Special TopicsMath and chemistry review,

solutions, and concentrations

http://www.youtube.com/watch?v=lMW5YYiEfgU

Outline

I. Metric system reviewII. Concentration of solutions

A. SoluteB. SolventC. Grams %D. Molarity (M)E. Molality (m)F. Osmolality and dissolutionG. Sample problems

Symbol prefix 100 1 one

   d deci* 101 0.1   tenth

   c centi* 102 0.01   hundredth

   m milli 103 0.001 thousandth

   µ micro 106 0.000 001 millionth

   n nano 109 0.000 000 001 billionth

   p pico 1012 0.000 000 000 001 trillionth

   f femto 1015 0.000 000 000 000 001

   a atto 1018 0.000 000 000 000 000 001

   z zepto 1021 0.000 000 000 000 000 000 001

   y yocto 1024 0.000 000 000 000 000 000 000 001

http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/index.html

King Henry Slider

Distance, volume, mass and temperature

Scientific Notation

• The notation is based on powers of base number 10. The general format looks something like this:

• N X 10x • where N= number greater than 1

but less than 10 and x=exponent. • Placing numbers in exponential

notation has several advantages. • Concise! • Easier math without your

calculator!• Let’s practice!

Now let’s talk about solutions Water is the most abundant liquid on the

earth and is necessary for all life. Because of water's great dissolving properties, any sample is a solution

containing solids, other liquids, and gases from the environment.

Aqueous solutions

• A solution is a homogeneous mixture of ions or molecules of two or more substances.

• Two parts• Solvent is the component

that is in the largest quantity (water)

• Solute is the component that is dissolved in the solvent.

Concentration

• A measure of how much of a substance (solute) is dissolved in another substance (solvent)

• To calculate [concentration]:

• Common usages of concentration:• Mass (m/v) conc. (grams%= grams per 100 ml, etc.)• Molarity (units are moles/L or M)• Molality (units are moles/kg or m)• osmolality

solventofamount

soluteofamountsoluteofconc .

gm %

• Let’s practice:• What is the gm% of 5.0 x101 g

of NaCl in 100 ml of water?• What about 0.009 gm in 100ml

of water?• Of the three ways we will

determine a solution’s concentration, this is the easiest one.

• Why?

In the case of dilute aqueous solutions, scientists often use the approximationapproximation:

We are walking sacks of dilute aqueous solutions.

Molarity (mol/L) = Molality (mole/kg solvent)This is a very close approximation for dilute solutions

because:

• 1) 1 kg of water 1 L

• 2) volume of solvent >> volume of solute therefore:– volume of solution volume of solvent– mass of solution mass of solvent

Molality (moles/kg)• What is a mole?• Avogadro’s number: 6.02 x 10 23

• Number of atoms or molecules necessary to reach atomic or molecular mass in grams

• How much does one mole of sodium weigh?

• Sodium Chloride?• Need periodic table

Above I show some pictures: one is a poor representation of a great Italian theoretician: the other a good representation of a poorly spelled Italian theoretician. I implore my students to notice the differences.

Dissociation factor to determine osmolality (dissolution)

• Ionic compounds that are soluble in water dissociate completely and exist in solution entirely as ions.

• Soluble ionic compounds are strong electrolytes.

• NaCl, KCl, MgCl2, HCl, CaCl2

• Molecular compounds such as sugars, proteins, fats and alcohol are non-electrolytes. They have no tendency to come apart, and they exist in solution entirely as aqueous molecules.

• What is the osmolality of a

5.4 % glucose solution?

• Is the solution hyperosmotic, hypo-osmotic, or isosmotic?

Question

Steps to complete the task• Write out the grams%• Convert to grams per liter (multiply by

1000ml/ 1 Liter)• Convert the grams to moles (you need

MW to do this! Multiply by 1mole/mw gms of substance)

• multiply by 1,000mmole/Mole to get mmole

• You now have mM/L . Multiply by 1L/1kg to convert to molality (mM/kg)

• Multiply by the dissociation factor and you now have osmolality! (glucose and proteins are “1”)

• The chorus breaks out into song!

Osmolality of a 5.4 % Glucose Solution

MW glucose = 180 gm/mol5.4 % = 5.4 gm 100ml5.4gm X 1000ml = 54 gm 100ml L L

Isosmotic—what would the cell do?

54 gm x 1 mol = .3 mol X 1000mmol =L 180 gm L 1 mole

Dissociation factor is one so: 300 mOsmkg

• What is the osmolality of a 3.0% NaCl solution?

Question

• Is the solution hyperosmotic, hypo-osmotic, or isosmotic?

Osmolality of a 3% NaCl Solution

For NaCl, 1 mmol = 2 mOsm513 mmol x 2 mOsm = 1026 mOsm = 1026mOsm/kg

LL mmolHyperosmotic—what would the cell do?In order to understand this concept, you need to learn about body fluid compartments!

MW NaCl = 58.53 % = 3 gm/100ml 3 gm X 1000ml = 30 gm 100ml L L

30 gm x 1 mol = .513 mol =L 58.5 gm L

513mmol/L