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Do Now • Take out your notes packet • Identify the solute, solvent and solution for hot chocolate
Do Now
• Take out your notes packet• Identify the solute, solvent and solution for
hot chocolate
Solution: What is a solution? Solute, solvent and solution
• The term ‘solution’ may be one you are familiar with outside of chemistry, but the definition for it in chemistry may be different than what you thought. In chemistry a solution is defined as “A homogeneous mixture formed from a solute dissolved into a solvent”. Remember that ‘homogenous’ means that it has the same consistency throughout the mixture. Solute and solvent may be new terms for you as well. A solute is what is being dissolved, and the solvent is the one that is doing the dissolving. Most of the time in class water will be our solvent.
• 2. Identify the solute, solvent and the solution for a pitcher of kool-aid
• Solute:____________• Solvent:________________• Solution:____________
What is happening when something is dissolving?
• Using an example to answer this question will be helpful. Let’s take a look at dissolving Sodium Chloride (NaCl), table salt. Salt in the crystal form is really organized and the ions are locked into place because of their opposite charges. When these crystals are introduced to water, which is polar, they begin to interact. The positive ends of the polar water molecule are attracted to the negative chloride ion. The negative ends of the water are attracted to the positive sodium ions. The water molecules begin to surround the individual ions and tear them away from the other ions in the crystal. These ions are kept separated from each other by the water molecules
Simulator
• This may help• Online version
Use the image on the previous page to answer the following questions
• 1. How is the left and right image different from each other?
• 2. What is the difference between how the water molecules surround the Na+ ions and how they surround the Cl- ions?
• 3. Let’s say all the water molecules were ‘busy’ separating the ions from each other. What would happen if you added more salt?
c) How much ‘stuff’ is dissolved: Saturated, unsaturated and supersaturated
• There is a limit to how much solute (‘stuff’) a certain amount of solvent (usually water) can dissolve. At a certain point the solution becomes saturated. An analogy may help make sense of the term ‘saturated’. A sponge, like a solution, can only hold so much ‘stuff’ before it cannot hold any more. When a sponge is saturated, it can no longer hold any more water. When a solution becomes saturated, it can no longer ‘hold’ (dissolve) any more ‘stuff’ (solute). If you were to add more solute it would simply sink to the bottom of the solution as an undissolved solid. This undissolved solute is called the precipitate, hence the saying: “If you aren’t part of the solution, then you’re part of the precipitate!” (lol). If a solution has dissolved as much solute as it can possibly hold, it is described as saturated. If it can still dissolve more solute, then it is described as unsaturated. Sometimes solutions can be ‘tricked’ into dissolving more solute than it should be able too. This is a special condition referred to as supersaturated. Rock candy is made from making use of a supersaturated solution of sugar and water. Carbonated water is another example. The closed bottle forces more CO2 to dissolve in the water by increasing the pressure. Once it is opened the CO2 slowly escapes as bubbles. This process can be sped up by the addition of a nucleation site (such as ones found on a Mentos candy). Remember, if it is supersaturated, all the ‘extra’ solute is actually dissolved, and not sitting at the bottom of the solution.
Cool demo
• Supersaturated solution used as a heat pack• Neat experiments using them• What happens when salt water starts to evapo
rate?
Where is the precipitate
OH NO!!!
Do Now
• Pick up a copy of the lab (for later) (due Tuesday when we return)
• Take out your notes packet• Try and come up with a way to remove the
permanent marker on the board with…
Factors affecting solubility; How can we make more stuff dissolve?
• ‘Like dissolves like’: Why doesn’t water and oil mix?
• The first factor to be examined for how to make more stuff dissolve can be remembered with the simple phrase ‘like dissolves like’. It refers to the polarity of a the solute and the solvent. If both are polar or if both are nonpolar, then the solvent will dissolve the solute. If they are different (one polar and the other nonpolar) then the solvent will not dissolve the solute. An example of this can be seen when you mix oil with water. Water is polar, and oil is nonpolar. This will result in neither dissolving into the other. You may have previously believed that oil and water didn’t mix because of their different densities, but YOU WERE WRONG! They do not mix because they have different polarities! The reason why the oil sits on top of the water is because it is the less dense of the two, but the reason they don’t mix is because of the difference in polarities. PLEASE, correct your friends and strangers alike from this point forth if they have this misunderstanding.
• The idea of ‘like dissolves like’ can also be applied to permanent markers. They are considered ‘permanent’ because you would probably try to clean them with water. The pigments in the marker are nonpolar, and water is polar. This means that when you try to clean the marker with water, the water will not be able to dissolve it! If you were a clever science student, you would try a different, nonpolar, solvent to clean it with (benzene or ethyl acetate AKA nail polish remover). PLEASE NOTE, before you go marking stuff up, it works best on clean, non-porous surfaces. Also, using these nonpolar solvents may also damage the thing you are trying to clean, so be careful…don’t ruin anything!
Let me show you
• Water and oil in slow-mo
Temperature and pressure: Why does soda go flat?
• Other factors that affect how much solute can dissolve in a solution are temperature and pressure. Temperature can have different effects on different types of solutes. For solid solutes, generally speaking, the higher the temperature, the more solute can be dissolved. This can be seen with salt and water. If you had some salt water with salt sitting undissolved at the bottom, you could heat the water up and more salt would dissolve. For gases, generally speaking, as temperature increases its solubility decreases. Think about what happens to soda once it gets warm…it goes flat. The water cannot hold as much carbon dioxide gas and it loses its fizz!
• - Pressure only affects gaseous solutes, and has no effect on solids. Gases become more soluble with an increase in pressure. You can think of it as the pressure is pushing more of the gas into the liquid. This is also why, once you open the pressurized soda bottle, the gases start to bubble out, there is now less pressure!
• On the axis to the side, draw a solid line showing the relationship between temperature and solubility for solids, and a dashed line for gas.
Solid line = solids
Dashed = gases
Practice problems
• 1. Nuclear power plants produce a lot of uncontaminated warm water which gets dumped into rivers. Why would this be a concern for the fishes that live in the water?
• 2. Scuba divers use pressurized tanks to store air so that they can dive deep underwater and still breath. The further down they go, the greater the pressure there is on their body. How would this affect the amount of air that would dissolve into the divers body?
• 2b. OH NO! AN EMERGENCY! RISE! RISE! RISE! A scuba diver experiences a problem and must immediately surface after spending a bit of time swimming very deep. What would happen to the amount of gas that could be dissolved in their blood when they surfaced?
2c. Why might this cause some issues for the diver?
For the solutes below, dissolved in water:
If temperature is increased, the solubility of this solute will:
If temperature is decreased, the solubility of this solute will:
If pressure is increased, the solubility of this solute will:
NH3 (g)
KCl (s)
Draw the structures of the compounds If they are molecular.
Is the solute polar or nonpolar or ionic?
Will this solute dissolve in water or benzene?
CH4
H2S
Do Now
• Take out the quarterly review you picked up on Friday
• Work on it• Questions? Throw a hand up
Major Topics
• -Periodic table• Organization of periodic table (atomic number, groups
vs. periods, principle energy levels, valence electrons)• Chemical properties based on location on periodic table• Classifying elements on the PT (metals, nonmetals,
metalloids, noble gases) (you wont have your PT for the quarterly)
• Calculating parts of the atoms (protons, neutrons, electrons, mass etc..)
• Various models of the atom (Dalton, Bohr, etc..)
Major Topics
• Bonding: • Determining types of bonds (END, metals and
nonmetals, etc.)• Determine bond polarity• Determining molecular polarity• Calculating: gfm, converting to and from
moles, %composition
Major Topics
• Equations• Balancing chemical equations• Determining type of reaction based on
equation• Stoichiometry: using balanced equations to
solve stoichiometry problems
How Mr. Donohue Would Study
• Read through each notes packet as a refresher– Came across stuff I totally didn’t remember:– Rewrite it out “Periods go across = PEL”
• Redo the homework problems– Cover the answers, check them– Not sure what the answer is…– Do some research and find out the right
answer• Retake the test(s) and see how I did
For right now
• I’ve put together some practice problems• Do them, check the answers, consult a friend
then me if you can not figure out the right answer
• Finished? Read over the notes packets, redo the homework packets/tests. Keep studying (20% of your grade is kind of a big deal)
Do now
• Pick up a copy of the lab and read it over• Homework: Finish the lab• Read the next topic in the notes
– C. Solubility Curves• TEST Friday after regents week (start reading
the rest of the packet)• DIDN’T TAKE LAST UNITS TEST: itll be a zero if
you don’t make it up…
Safety
• Goggles• Pretty safe lab…don’t do anything silly• No rough housing• No squirting each other with water…
The Story
• Someone stole my Pez Dispenser!• Luckily they left a ransom note• The ink from the note will be analyzed and
compared to the pens found in the 4 suspects offices
Big Idea• Markers are a mixture of different pigments, some
of which are really polar and some of which are really nonpolar
• This difference will be used to separate the pigments– Polar pigments will dissolve in and travel with the water– Nonpolar pigments will stick to the nonpolar filter paper
• This will allow us to examine the pigments in different pens and ID the pen used to write the ransom note
GO DO IT!
• Homework: Finish the lab• Read the Rest of the notes packet over the
next 9 days…
Do Now
• A bit-o-review• Solute – Solvent – Solution…• To increase solubility of a solid solute you
_________ temperature• To increase solubility of a gaseous solute you
can ___________ temperature OR __________ ______________
• CSI Lab due tomorrow
c) Solubility curves
Go Ahead and take out your RT + Notes packet
c) Solubility curves• Solubility curves show the solubility of different solutes in water at different
temperatures. The lines represent how much of that solute can dissolve in 100. grams of water at the given temperatures. Don’t let the unit ‘g solute/100.g H2O’ throw it off. Remember, if we used more water we could dissolve more solute, therefore we need to pick a specific amount of water used to dissolve the solute. 100. Grams is a nice round number. If you used 200. grams of water instead, you would be able to dissolve twice as much solute. If you used 50. g instead of 100 g, then you could only dissolve half of the solute indicated on the graph.
• You also need to be able to use this chart to determine if a solution is saturated, unsaturated or supersaturate. Remember, the lines represent saturation, so if you were given a point and it fell directly on the line, then that solution is saturated. If your point fell below the line, that means more solute could be dissolved in the solution, making it unsaturated. If your point fell above your line, then that solution is holding more solute than it is supposed to be able to hold and is supersaturated.
• Example: • How many grams
of NaNO3 are required to make a saturated solution in 100 g of water at 30oC?
• Start at 30oC, move up to the NaNO3 line. Scoot across to Solute (g).
• 96 grams can be dissolved in 100 g of water at 30oC.
• How many grams of NaNO3 are required to make a saturated solution in 50 g of water at 30oC?
• Since in the last question, it was determined that 96 grams of NaNO3 can be dissolved in 100 g H2O, since 50 g is half as much water, only half as much NaNO3 can be dissolved. Therefore, 96/2 = 48 g of NaNO3 can be dissolved in 50 g H2O.
• What is the solubility of HCl in 100 g of water at 70oC?
• • Start at 70oC, up
to HCl and across: 52 g HCl in 100 g H2O @ 70oC
• What kind of solution do you have if 80 grams of KClO3 are dissolved in 100 g of water at 40oC?
• Start at 80 grams, and 40oC. See where the lines intersect with respect to the KClO3 line. They intersect far above the KClO3 line. At 40oC, the solubility of KClO3 is only 16 grams in 100 g of water. This solution is supersaturated.
• For the above solution, what can you do with temperature and amount of KClO3 to make the solution saturated?
• If you want to dissolve 80 g of KClO3 in 100 grams of water, the table says you need to heat the solution to 75oC (adding an additional 35oC to the current temperature of 40oC).
Practice in the notes
• Your turn!
• 1) As the temperature decreases, the solubility of gases
• 2) As the temperature decreases, the solubility of solids in liquids
• 3) Which of the salts on Table G is the least soluble at 90oC
• 4) Which gas on Table G is most soluble at 60oC?
• 5) Which salt on Table G shows the least change in solubility between 30oC and 70oC?
• 6) 108 g of KNO3 at 60oC
• • 7) 20 g of NH4Cl
at 30oC
• 9) What is the solubility of NaNO3 in 100 grams of water at 40oC?
• 10) How many grams of KClO3 can be dissolved in 1000 g of water at 30oC?
• 11) What is the solubility of NaCl in 50 grams of water at 70oC?
• How many grams of solute must be added to a solution containing 30 g of NH4Cl in 100 g of H2O at 90oC in order to make it a saturated solution?
• A solution contains 80 g of KNO3 in 100 g of H2O at 80oC. To what temperature must the solution be lowered in order to make it a saturated solution?
• Consider a saturated solution of NaNO3 in 100 g of H2O at 70oC. If the solution is cooled to 20oC, how many grams of solute will precipitate?
• 15) How many grams of solute will precipitate if a saturated solution of NaNO3 in 50. g of water at 30oC is evaporated to dryness?
• 16) At what temperature do KCl and HCl have the same solubility?
Do Now
• TURN IN YOUR CSI LAB• Take out your notes packets and reference
tables• Open your notes to page 8/9• Leave them open for now• Notes check on this periods stuff before you
leave
Neighbor Practice
• Using R.T. G, answer the following regents questions.
• Answers are on the back to check as you go• Quiz on this stuff tomorrow• After this, we are going to get into
concentrations, so make sure through page 9 is done in your notes
• HOMEWORK: Make sure to finish the lab, READ AND DO PAGES 10, 11, 12!
Notes check time
• On solubility• Can use your notes
Do Now
• TURN IN YOUR CSI LAB (only 7 people did)• Take out your notes, opened to page 8-9• Pick up a copy of the lab and read over the
background
Any Questions on The Homework
• Molarity = moles/liter• Dilutions: M1V1= M2V2
• Percents?• Ppm?• Quiz tomorrow on it…
TONIGHTS HOMEWORK
• READ AND DO PAGES 10, 11, 12!• HONORS: Also read pages 14+15• Lab due Monday
Safety:• Bunsen burner safety• Heating things up over the Bunsen burner, be
careful not to burn yourself• ‘Snowing’ = record the temperature
– Not a couple of particles, but really looks like its snowing• DO NOT EMPTY ANYTHING OUT BETWEEN TRIALS
– Just reheat it to dissolve it all again…• Measuring out the correct mass is critical, do a good
job
Big idea
• We have an unknown salt• We are going to create a solubility curve for it• Each group will have a different amount of salt
to dissolve• Collect data as a class• Compare our graph to the R.T. and ID which it
best matches with
Assigned grams of salt / 10.0 g of H2O
Average Crystallization Temperature (oC)(X-Axis on Graph)
Grams of salt100 grams H2O(Y-Axis on Graph)
3.0 g 4.0 g 5.0 g 6.0 g 7.0 g 8.0 g
Assigned grams of salt / 10.0 g of H2O
Average Crystallization Temperature (oC)(X-Axis on Graph)
Grams of salt100 grams H2O(Y-Axis on Graph)
3.0 g 4.0 g 5.0 g 6.0 g 7.0 g 8.0 g
Notes Check Time
• Just on Solubility, you may use your notes• ~9 minutes
Do now
• TURN IN YOUR Magical Mystery Salt LAB• Take out your notes packet and open to pages
8+9
Concentration of solutions; How do we measure how ‘concentrated’ a solution is?
• Being able to quantify how concentrate a solution is, is very important. There are a number of different ways to measure this, and each is easier to use in different situations.
a) Molarity: Moles of solute / Liter of solution
• As suggested by its name, molarity has to do with how many moles are dissolved in a liter of solution and the unit used to measure it is called molar. For example, if you had a 1 molar solution of NaCl (aq), you know you would have one mole of NaCl for every liter of solution. This way of measuring concentration is the most common in the chemistry lab.
a) Molarity: Moles of solute / Liter of solution
• To experimentally determine the molarity of a solution:
• 1) Determine the volume of solution you have• 2) Determine how many moles of solute are
dissolved in the solution by• a) Evaporating off the solvent• b) Weighing the solute• c) Dividing the mass of the solute by the
formula mass of the solute• 3) Molarity (M) = moles of solute/L of solution.
Molarity Simulator
• Show values, lets crunch some numbers!• File• internet
Practice:
• 1. What is the molarity of a solution if it contains 2.0 moles of KNO3 in 4.0 L of solution?
• 2. What is the molarity of a solution if it contains 2.0 moles of NaCl in 250. mL of solution?
• 3. What is the molarity of a solution if it contains 20. grams of NaOH in 2.0 L of solution?
Practice
• 4. How many moles of NaOH are needed to make 4.0 L of a 0.50 M solution of NaOH?
• 4b. How many grams of NaOH would this be?
• 5. How many grams of KCl are needed to make 500. mL of a 0.100 M solution of KCl?
i) Making dilutions
• Making dilutions is a crucial skill for a chemist, and is one that I as your teacher use often. For example, the hydrochloric acid that we order comes in a concentration of 6.0 molar, or 6.0 M. This is very concentrated and needs to be diluted for what we do in lab.
i) Making dilutions• Before we get into the math, let’s think conceptually about
what is happening when we dilute something. I pour out a little bit of the 6.0 M HCl into a beaker. As long as I don’t spill any of this solution, the total amount of HCl in that beaker shouldn’t change. If I add more water to it, there is still the same number of moles of HCl in the beaker, it just makes it less concentrated. Therefore we know that the moles that we start with (n1) has to be the moles that we end up with (n2). To figure out the initial number of moles we rearrange the molarity equation to solve for moles and we get;
i) Making dilutions
• Molarity1 x Liters1 = n1
• Molarity2 x Liters2 = n2
• Since the moles we start with has to equal the moles we also get:
• n1 = n2
• Now we can set the first two equations equal to each other and we get
• Molarity1 x Liters1 = Molarity2 x Liters2 OR M1 V1 = M2 V2
i) Making dilutions
• Practice• 1. You start with 1L of 6M HCl (aq) and dilute it to 6L.
What is the concentration of this new solution?• • 2. How much .1M NaCl (aq) solution can you make from
100.mL of 2M NaCl (aq)?• • • 3. How many milliliters of 6.0 M HCl (aq) are needed to
make 100.mL of .1M HCl (aq)?
c) Percent by volume: (volume solute/volume solution) x 100
• Just like percent by mass, except you use the volumes of solute and solution. This is used for liquid solutes, like alcohol. The percentages of alcohol on alcoholic beverages are given by volume. Generally speaking, if something is 50% alcohol by volume it is flammable. This is where the term proof comes from…back in the old days, a bartender might water down the whiskey to save money. Whiskey was supposed to be at least 50% alcohol by volume. If a patron demanded proof that the whiskey wasn’t watered down, a sample had to be touched with a flame. If it wouldn’t burn, the bartender might be shot! Or just run out of busines
Public Service Announcement: Do not drink underage, or at all! Alcohol is a poison
d) Parts per million: (mass of solute/mass of solution) X 1 000 000
• This unit is similar to percentages. Percentages give you the part out of 100, whereas ppm gives you the parts out of 1,000,000. It is used to determine trace amounts of dissolved ions in drinking water. Established toxic threshold levels are reported in ppm or sometimes ppb (parts per billion) if it is a particularly nasty toxin. It is also used to measure the concentration of particulates in the air. Air pollution is measured in parts per million, as is dust in a clean room at an electronics manufacturing plant.
d) Parts per million: (mass of solute/mass of solution) X 1 000 000
• What is the concentration, in ppm, of lead ions in 100. g of tap water with 0.0000450 g of lead ions dissolved in it?
• ppm = (g of solute / grams of solution) X 1 000 000
• = {(0.0000450 g) / (100. g)] X 1 000 000 • = 0.45 ppm
Concentration Practice
• 1) A sample of tap water is analyzed and shown to contain 0.015 grams of lead ions per 10 grams of solution. Calculate the concentration, in ppm, of this solution.
Concentration Practice• 2) Lead is a heavy metal that is found
in car batteries. If they are disposed of in the dump, they can leach the lead out and contaminate the ground water. The EPA has been called in to test the water around one particular dump and found that every 1000. g of groundwater tested contains 0.00027 grams of lead. The EPA’s legal limit on lead concentration is 0.015 ppm. Does the dump site break the legal limit? Show your work.
Concentration Practice
• 3) Calculate the percent by mass of a solution that contains 35.8 grams of Na2SO4 in 136.3 grams of solution.
Concentration Practice
• 4) Calculate the percent by volume of a solution that contains 4.55 mL of ethylene glycol in 7.83 mL of solution.
Do Now
• Pick up a copy of the notes check and get started
• treat it like a quiz (done individually)• You will have 10 minutes from the bell• Bonus: Which of the following 1 molal
solutions will have the LOWEST BOILING POINT:– NaCl C6H12O6 K3PO4 Cu(NO3)2
4) Conductivity; Electrolytes vs. nonelectrolytes
• Electrolytes: Most ionic compounds and many acids dissolve well in water. These are called electrolytes, because they cause the solution to conduct electricity due to the free-moving ions. They ionize 100% in water to yield ions in a reaction that resembles a decomposition reaction. The reaction is called dissociation, and it is a physical change, not a chemical change. The more ions a solute breaks up into, the more conductive it can become (as well as the higher the boiling point and the lower the freezing point of the solution will be).
• NaCl (s) Na+1 (aq) + Cl-1 (aq)• One mole of sodium chloride dissolves to form one mole of sodium ions
and one mole of chloride ions (2 moles of dissolved ions total).• CaBr2 (s) Ca+2 (aq) + 2 Br-1 (aq)• One mole of calcium bromide dissolves to form one mole of calcium ions
and two moles of bromide ions (3 moles of dissolved ions total)
See how they break up
• http://phet.colorado.edu/en/simulation/soluble-salts
• File• Conductivityfile• http://phet.colorado.edu/en/simulation/
sugar-and-salt-solutions
Practice:Ionic Compound # of and identity of CATION # of and identity of ANION Total # of Ions KHCO3
Fe(C2H3O2)2
Mg(OH)2
CaBr2
Nonelectrolytes: • Substances formed from covalent bonding (nonmetals bonded
together) do not dissolve into ions upon entering the water. These include polar molecules that dissolve, but do not ionize. These include sugar (C6H12O6, C12H22O11), antifreeze (CH2OHCH2OH ) and alcohol (C2H5OH). These have less impact on the melting and boiling point of a solution than ionic compounds do, because they do not break up any further.
• C12H22O11 (s) C12H22O11 (aq)• One mole of sucrose dissolves to form one mole of dissolved
sucrose. No ions are formed, so no electricity can be conducted.
Colligative properties: What happens to the properties of the solution when stuff is dissolved?
• - COLLIGATIVE PROPERTIES OF SOLUTIONS are physical properties of solutions that depend on the concentration of solute in a given amount of solvent.
• a)Freezing Point Depression: The freezing point of water decreases as solute is added to it.
• b) Boiling Point Elevation: The boiling point of water increases as solute is added to it.
Anitfreeze• Antifreeze. It isn’t just for breakfast anymore. Actually, it never was, as it is a deadly poison. As it metabolizes, it forms razor-sharp
crystals in the kidneys, liquefying them and leading to an excruciatingly painful death. Keep it away from children and pets. There is an antidote that prevents the crystals from forming, but it has to be administered before it metabolizes to that point.
• It might not be good to drink, but it is excellent at preventing the water coolant in your car’s engine from boiling or freezing. In hot weather, going up a steep hill, your car’s engine produces a lot of heat. Water flowing through pipes in the engine carries heat out of the engine, where it passes through the radiator and cooled before being sent back to the engine. The temperature might reach 100oC, the boiling point of water. If the water is allowed to boil, the pressure of the steam that is produced might cause the engine to crack. In addition, steam is only half as efficient per gram as liquid water at carrying heat away from the engine.
• This water coolant is still in your engine when the weather is cold. If the car is parked outside in sub-freezing temperatures, the water in the engine’s coolant pipes might freeze. Water expands when it freezes, and this would cause the pipes to burst, causing expensive repairs and towing costs.
• Adding a solute like antifreeze helps tremendously, because the solute makes it a lot harder for the water to boil or freeze. Remember, when solutes dissolve, water molecules hold on to the solute particles to keep them apart. To boil, the water has to be detached from the solute particles, which requires adding more energy than usual. When dissolving solutes in water, the boiling point increases. The more solute that is dissolved, the higher the boiling point will go.
• When a liquid like water freezes, it does so by forming a crystal lattice. The solute particles interfere with this process, meaning that the solution has to be cooled down to a lower temperature than the normal freezing point for it to freeze. The more solute that is added, the lower the freezing point will drop. This is why salt is dumped on the roadways during the winter! The road has snow packed on it. A truck comes along and dumps salt on the snow. When cars drive over the salted snow, the pressure and friction from the tires causes the snow to melt. The salt dissolves in the freshly melted snow, and prevents it from refreezing. The salt that is the least expensive to use is crushed halite salt (NaCl). More and more communities are using a different salt, calcium chloride (CaCl2). This forms round pellets; you may have seen them on the road or on a walkway. CaCl2 is more effective than halite salt at preventing the water from refreezing. NaCl breaks up into two ions (Na+1 and Cl-1) when dissolved. Calcium chloride breaks up into THREE ions when dissolved (one Ca+2 ion and two Cl-1 ions). The more ions that are dissolved in the water, the more they will interfere with water freezing, and the freezing point of water will drop even further…or the less salt you will need! The more ions that form, the greater the impact it will have on the melting and boiling points! Also, the more solute dissolved in solution, the greater the impact on the melting and boiling points.
Antifreeze
• Without antifreeze: water would boil from the engine and pressure would build until it broke
• Water would freeze in the winter and break the pipes and such (ice expands)
Antifreeze
• Dissolve stuff: • boiling point increases
(now the water wont boil)
• Freezing point goes down: it has to get REALLY cold for it to freeze
Salt on the roads
• Dissolving salts lower freezing point
• If the ice is at -2oC and you drop its freezing point by adding salt to -6oC, its going to melt!
Questions
• 1. Does adding salt to a pot of water really make it boil faster? Explain.
• (actually, you would need about 240 grams, over half a pound, of NaCl in 4 qts of water to make it boil 2 degrees higher)
Compound Ionic Or Molecular?
Electrolyte or Nonelectrolyte?
How many particles the compound breaks up into
Rank in order of which one affects the boiling and freezing points the least to most 1 = affects them least 4 = affects them most
BaBr2
LiF
C2H6O
Fe(NO3)3
• ______1) Which of the following 1 molal aqueous solutions will have the highest boiling point?
• a) NaCl (aq) b) C6H12O6 c) K3PO4 d) Cu(NO3)2
• • ______2) Which of the following 1 molal aqueous solutions will
have the lowest boiling point?• a) NaCl (aq) b) C6H12O6 c) K3PO4 d) Cu(NO3)2
• • ______3) Which of the following 1 molal aqueous solutions will
have the highest freezing point?• a) NaCl (aq) b) C6H12O6 c) K3PO4 d) Cu(NO3)2
• • • ______4) Which of the following 1 molal aqueous solutions will
have the lowest freezing point?• a) NaCl (aq) b) C6H12O6 c) K3PO4 d) Cu(NO3)2
• ______5) Which of the following aqueous solutions will have the highest boiling point?
• a) 500 g solute in 1000 g solvent b) 500 g solute in 500 g solvent• c) 1000 g solute in 500 g solvent d) 1000 g solute in 1000 g solvent• • ______6) Which of the following aqueous solutions will have the lowest
boiling point?• a) 500 g solute in 1000 g solvent b) 500 g solute in 500 g solvent• c) 1000 g solute in 500 g solvent d) 1000 g solute in 1000 g solvent• • ______7) Which of the following aqueous solutions will have the highest
freezing point?• a) 500 g solute in 1000 g solvent b) 500 g solute in 500 g solvent• c) 1000 g solute in 500 g solvent d) 1000 g solute in 1000 g solvent• • ______8) Which of the following aqueous solutions will have the lowest
freezing point?• a) 500 g solute in 1000 g solvent b) 500 g solute in 500 g solvent• c) 1000 g solute in 500 g solvent d) 1000 g solute in 1000 g solvent
• D) Based on this chart, to the right:• 1) If your cooling system has a
capacity of 14 quarts, how many quarts of antifreeze will be needed to protect your car’s engine down to -28oF?
• 2) Based on the bottom chart, does
dissolving a solute in water provide a greater protection against freezing or against boiling? Explain, using the information on the chart.
Determine the freezing and boiling points of solutions
• A) Freezing Point Depression: For every mole of particles that is dissolved in 1 kg of water, the freezing point decreases by 1.86oC. Ionic compounds (made of a metal and nonmetal or polyatomic ion) will break up to form 2 or more ions in water. For example, a 1 m solution of NaCl will have a 2 m concentration of particles (because it breaks into 2 ions). A 1 m solution of CaCl2 would have a 3m concentration of particles because of the 1 Ca+2 and the 2 Cl- ions. Molecules (made of covalently bonded nonmetal atoms, remember?) do not break up into ions when dissolved. 2 m antifreeze (ethylene glycol) contains 2 m of dissolved particles.
Determine the freezing and boiling points of solutions
• Tf = Kfm
• Tf = freezing point depression,
• Kf = freezing point depression constant (1.86oC/m for water)
• m is the molality (moles solute/kg solvent) of the dissolved particles, taking into account electrolytes.
• Ex. What is the freezing point of a 2.0 m solution of CaCl2 (aq)?
• CaCl2 is ionic, so it ionizes to form three ions (1 Ca+2 and 2 Cl-1).
• 2.0 m of solution has 2.0 X 3 = 6.0 m of dissolved particles.
• Tf = Kfm = (1.86oC/m) X (6.0 m) = 11 oC• Since water freezes at 0oC, the new freezing point
will be depressed by 11oC: • 0oC – 11oC = -11oC
• Ex. What is the freezing point of a 3.0 m solution of C12H22O11 (aq)?
• C12H22O11 is made entirely of nonmetals, so it is a nonelectrolyte.
• 3.0 m of solution has 3.0 m of dissolved particles.• Tf = Kfm = (1.86oC/m) X (3.0 m) = 5.6 oC• Since water freezes at 0oC, the new freezing point
will be depressed by 5.6oC: • 0oC – 5.6oC = -5.6oC
B) Boiling Point Elevation:
• For every mole of particles that is dissolved in 1 kg of water, the boiling point increases by 0.52oC.
• Tb = Kbm
• Tb = boiling point depression, • Kb = boiling point depression constant (0.52oC for
water) • m is the molality of the dissolved particles, taking
into account electrolytes.
• Ex. What is the boiling point of a 2.5 m solution of NaCl (aq)?
• NaCl is ionic, so it ionizes to form two ions (1 Na+1 and 1 Cl-1).
• 2.5 m of solution has 2.5 X 2 = 5.0 m of dissolved particles.
• Tb = Kbm = (0.52oC/m) X (5.0 m) = 2.6oC• Since water boils at 100oC, the new boiling point
will be elevated by 2.6oC: • 100oC + 2.6oC = 102.6oC
• Ex. What is the boiling point of a 1.5 m solution of CH2OHCH2OH (aq)?
• CH2OHCH2OH is made entirely of nonmetals, so it is a nonelectrolyte.
• 1.5 m of solution has 1.5 m of dissolved particles.• Tb = Kbm = (0.52oC/m) X (1.5 m) = 0.78oC• Since water boils at 100oC, the new boiling point
will be elevated by 0.78oC: • 100oC + 0.78oC = 100.78oC
• E) Calculate the phase change points of the following solutions:
• • 1) Freezing point of 0.500 m C6H12O6 • • 2) Boiling point of 3.00 m KCl • • 3) Freezing point of 2.00 m Na2CO3 • • 4) Boiling point of 0.100 m Al(NO3)3
• • 5) Freezing point of 1.50 m C2H6O2
Do Now
• Turn in Your Magical Mystery Salt Labs• Pick up a copy of the next units work packet• Take out your notes pack and open to the
review
Solutions Review
• 1) What is a solution?• • • • 2) How does a solution form?• • • • 3) What is solubility?
• 4) Fill in the chart below with either increases, decreases, or remains the same for changing the following factors on the SOLUBILITY of the solute in water:
Solute Increasing Temperature
Decreasing Temperature
Increasing Pressure
Decreasing Pressure
CO2 (g)
NaCl (s)
5) Using Reference Table G, determine the solubility of:
a) NaNO3 in 100 g of water at 30oC
c) KNO3 in 100 g of water at 40oC
b) NaNO3 in 200 g of water at 30oC
d) KNO3 in 50 g of water at 40oC
• 6) Using Reference Table G, determine if the following solutions are saturated, unsaturated or supersaturated. If they are anything but saturated, list two things you can do to make them saturated (include numbers).
Solution (in 100g H2O)
Sat, Unsat, Supersat +/- how many oC to make saturated?
+/- how many g to make saturated?
40 g of KClO3 at 50oC
110 g NaNO3 at 45oC
70 g KNO3 at 60oC
70 g NH4Cl at 70oC
7) Calculate the molarities of the following solutions:
• a) 120 g NaOH in 500. mL of solution• • • b) 3.0 moles NaCl in 750. mL of solution• • • c) 50.0 g of NaNO3 in 2.5 L of solution
8) Calculate the number of grams of solute needed to make the following solutions:
• a) 2.00 L of 0.50 M NaBr (aq)• • • b) 250. mL of 3.0 M KNO3 (aq)• • • c) 350. mL of 0.10 M HCl
9) Calculate the following concentrations:
• a) In ppm, of 0.044 grams of mercury ions in 200. g of solution
• b) In % by mass, 3.88 grams of NaCl in 10.0 g of solution
• c) In % by volume, 5.63 mL of ethyl acetate in 7.89 mL of solution
10) HONORS Calculate the melting point and freezing points of the following solutions:
Molality of solution: Freezing point Boiling Point
1.5 m C6H12O6
2.7 m NaCl
3.3 m CaCl2
8 m C2H6O2
Okay, lets look at concentrations again…
• What is the ppm of HCl if a solution has 365 grams of HCl dissolved in 3 kg of solution?
Okay, lets look at concentrations again…
• What is the percent of HCl if a solution has 365 grams of HCl dissolved in 3 kg of solution?
What is the molarity of a solution that has 365 grams of HCl dissolved in 4 liters of solution?
How much 1.0 M HCl solution can you make from that?
Any Questions?
P1+7 P3 Topic Homework (Due at the beginning of the next period)
2/5 2/5 Acids, Bases and their propertiesRead next topic; 2)Indicators +
3)pH. Do the practice
2/6 2/6 Indicators and pH Read next topic 4)Acid and Base Neutralization, Do the practice
2/8 2/7 Acids, bases and indicators lab
2/8 2/7 Acids, bases and indicators lab Finish the lab (due 2 days later)
2/6 2/8 Acid-Base Neutralization
2/7 2/12 Titration practiceRead the next topic; 5) Bronsted-
lowryDo the practice
2/12 2/11 Titration lab 2/12 2/11 Titration lab Finish the lab (due 2 days later)
2/11 2/13 Bronsted-Lowry Acids and bases Do the review problems and study for the test
2/13 2/13 Review Study for the test2/14 2/14 Test
