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Academic Chemistry

SolutionsNotes

Unit #13 Test Date: 3 /yl

cinc che .p works.co &

Resource Unit 13

Unit 13 Water

Water (H?01 - We can learn about water by looking its physical

_ V j f . Understanding the properties of water

helps us understand mixtures containing water.

1. Lewis structure of water.

U LI l roms

q , r2. Water has a P ft v shape because of its electron arrangement

3. Water is POLAR. Electronegativity of O 3.5 H

The difference in electronegativity makes water polar.

l i|\Ve)y/ ando A polar compound has jOflS>l \VeAy

charged parts

4. Oxygen (-) is attracted to hydrogen (+) and vice versa forming

STRONG h drogen bonds between water molecules

o This explains water s boiling point HIGH heat

iof ap zallon, and HjGHsurface tension.

5. WATER is known as the UNIVERSAL SOLVENT because it is a

stable, polar liquid at normal temperatures.

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Water Unit 13

Density of H20State Temp (°C) Density (g/cm3)Vapor 100 0.9584

Water 50 0.9881Water 10 0.9997Water 4 1.0000*

ICE 0 0.9168

Above: The solid (frozen!) state of water is

liquid state of water.

/ rc< dense than the

ICE (H?Q)

When frozen, water has a 3D shape like a honeycomb. At 0°C, hydrogen

bonds between molecules stabilize naturally in this crystal shape. This

shape has more empty space (volume) than the liquid state. This is why

the density of ice is lower than the density of wat Ljmaking it FLOAT!

- TY\

l Hydrogen Bonds in an Ice Crystal

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Unit 13 Solutions

Solutions

¦ A solution is a homogenous mixture consisting of 2 parts:

a « 0 .

1. SOLVENT - ;P ( S I f & medium,

substance in LARGEST amount, usually liquid. Water is the

universal sol ent.

2. SOLUTE - substance being. isSoLV &P

substance in SMALLEST amount, usually a solid.

¦ Aqueous solution - a solute (solid, liquid, or gas) dissolved in

water.

¦ SOLVATION- the action of a solute dissolving into a

SO LU E WT

¦ SOLUBILITY is the number of

that dissolve in a given quantity of a solvent (usually 100 g) at a

given temperature producing a saturated solution.

o saturated solution - contains the

amount of dissolved solute at a constant temperature.

Solubility of Liquids

¦ -when two liquids are able to

dissolve into one another (ex. water and alcohol)

¦ ) yvi rVIIS. - when two liquids are VOT

able to dissolve into one another (ex. oil and water)

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Solutes / Electrolytes Unit 13

Types of Solutes in Water

Solute

Ionic(meta l/nonmetal)

Very Polar

Covalent(nonmetal/nonmetal)

Polar Nonpolar

Dissolvein water?

AfO

Conductselectricity > o Afo

Q: What is an electrolyte?

A: A substance that breaks into ions (+ and - charged particles) when

dissolved in a Solven OR

and therefore conducts electricity.

So IC compounds are

and covalent compounds are NONELECTROLYTES

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Unit 13 Solubility

Factors affecting solubility - IF & HOW MUCH DISSOLVES

1. TEMPERATURE- as temperaturet solubility 1• gases are the opposite; as temp t, gas solubility

2. NATURE {POLARITY) of S LU E and SqLV6 T

• polar solvents dissolve polar solutes

• nonpolar solvents dissolve nonpolar solutes

• So... dissolves

3. PRESSURE (for gases ONLY) - 1 6f£ASe, in pressure

results In in solubility of a gas in a

liquid (exa ple. godo, )

Factors affecting RATE of solubility HOW FAST IT DISSOLVES

1. TEMPERATURE - greater kinetic energy, more collisions, solute

dissolves faster.

2. AGITATION (stirring) - more contact with surface of solute,

solute dissolves faster

3. SIZE of particles SWAUEft _ particles expose more

surface area of the solute. So, the solute dissolves faster.

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Properties of Solutions Unit 13

Saturation of Solutions

1) Saturated solution - contains the X(//T) amount

of solute for a given amount of solvent at a constant temperature.

I s S2) Unsaturated solution - contains solute than a

SATURATED solution

3) Supersaturated solution - a solution that contains /ftDtLBSOLUTE than it should be able hold at a constant temperature.

Occurs when a saturated solution cools slowly and crystallization

has not occurred (yet).

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Unit 13 Solubility Graphs & Curves

Solubilities of Some Substances in Water at VariousTemperatures

Substance Formula

Solubility (grams/100g H2O)0 C 20°C 50°C 100°C

Potassium Chlorate KCIOs 4.0 7.4 19.3 56.0

Potassium Chloride KCI 27.6 34.0 42.6 57.6

Sodium Chloride NaCI 35.7 36.0 37.0 39.2

Sodium Nitrate NaNOs 74 88.0 114.0 182Silver Nitrate AgNOs 122 222.0 455.0 733Lithium Bromide LiBr 143.0 166 203 266.0

Sucrose (table sugar) C12H22O11 179 230.9 260.4 487Hydrogen H2 0.00019 0.00016 0.00013 0.0

Oxygen 02 0.0070 0.0043 0.0026 0.0

Carbon Dioxide CO2 0.335 0.169 0.076 0.0

Practice Questions:

1. Do the last three substances in the table bove increase or decrease

solubility in water as temperature increases? Why?

2. Is a solution of 45 grams of KCI dissolved in 100 grams of water at 50 °Cunsaturated, saturated, or supersaturated?

3. Is a solution of 222.0 grams of AgN03 dissolved in 100 grams of water at 20°C unsaturatecL saturated, or supersaturated?

4. Is a solution of 3.5 grams of KCI03 dissolved in 100 grams of water at 0 °C

unsaturated, sa urated, or supersaturated?

5. Which solute has the highest solubility at 20 °C?

Sl 'rtj e,

6. Which solute has the highest solubility at 50 °C?

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Solubility Graphs & Curves Unit 13

Solubility Curves - compare the solubility of a solute (solid, liquid, or

gas) in a solvent to the temperature of the solvent.

athat lies ONJJie solubility curve.

solution contains a mass of solute

...with a solute mass BELOW the curve is

...with a solute mass ABOVE the curve is

o<N

Eoo

sai i it l

ni.s atirr ate d

Temperature C

Discussion of GRAPH AT RIGHT1. For gases, how does solubil ty change

as temperature increases?

$o iV\ ( ofease

2. Is this a direct or inverse relationship?

3. The 4 gases in this graph all behavesimilarly. As temperature increases, gasvolume ( no EASES)/ DECREASES ), sothe density of the gases drops, and thegases escape the system!

GAS SOLUBILITY

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Unit 13 Solubility Graphs & Curves

Questions1. Which solute dissolves best when

the water is 10 °C?

nIO*} ICI

2. Which solute has the lowestsolubility at 60 °C? r

o££oo

3. How much KCI dissolves in 100 mlof water that is 45 °C?

iDq /O

CO

How much KN03 will dissolve in 500ml of water that is 45 °C? v 5

i5a* 5.,100*1 500 r*L

00 10 20 30 40 50 60 70 80 90 100

Temperature (°C)

5. If you stir 50 grams of KCI03 in 100 ml of water that is 70 °C, will all of itdissolve?

I\l09 190*1 OtA 3t)J

6. If you stir 100 grams of NaNOs in 100 ml of water that is 20 °C, how manygrams of it won't dissolve?

.So

7. How many grams of NaCI will dissolve in 200 ml of 90°C water?

|0 L L li8. You have 80 grams of KN03in 100 mLof H20 at 40°C. Is this unsaturated,

saturated, or supersaturated?

9. If you had 50 ml of water as solvent, how many grams of solid NaCI could

you diss lve in 100°C water?

v\,\ 40q XJ3IOO*

10. How many grams of CaCl2 are needed to saturate 100 ml of water at 20 °C?

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Concentration and Molarity

CONCENTRATION of a solution

Unit 13

Two common ways to describe concentration in a solution

1. Dilute solution -contains a L Q concentration

of solute

2. Concentrated solution -contains a Irl 1

concentration of solute

In Chemistry we will use to better

express concentration of solution

Molarity (M) - number of moles of solute dissolved per liter of solution

iv noU-S of Soly-

M = L * S l plOkl

S Example - 2.5 M HCI means:2.5 moles Hydrochloric acid

1 liter of solution (water

Practice: Find the molarity of a solution that contains 0.35 moles of

ammonium iodide (NH4I) in 100_mL of solution.mL 3 -fo l« fc L

0.355.1 q '

* i s'3 4

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Unit 13 Concentration and Molarity

• Practice: Find the molarity of a solution that is made by dissolving

53.0 g of potassium chloride (KCI) in Sj O ml of solution.

53vk£U I-I tel . O.IVM

jy\ . -o. ooo L

I.HrAkct

Practice: How many grams of sodium chloride (NaCI) are needed to

make 1.500 L of a 2.00 M solution?

= 3,0 r o|

58. W n5jKl»cl|

• Practice: What volume of 1.25 M sodium hydroxide (NaOH) can be

prepared using 60.0 grams of sodium hydroxide?

rvto'

4A W g_ I.SOrwl

l.ismV

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Dilution Unit 13

In Chemistry, we often need solutions of various molarities depending

on the task at hand. We can dilute a concentrated solution with a

solvent to obtain the molarity of solution we need.

When diluting, moles of solute t-es tsfnT cAtAr fe 1

A solution is diluted by adding So bt

We can express this change in a formula to predict our needs:

Mi = molarity (mols/L) of initial solution

Vi = volume (mL or L) of initial solution

M2 = molarity of new solution

V2 = volume of new solution

Practice: If you were preparing Oj mL of 0.40 M magnesium

sulfate from an initial solution of 2.0 M magnesium sulfate, how

much initial solvent would you use?

ool -V, * o.1o -o l00L

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Unit 13 Dilutionl r

• Practice: If you dilu g O ml of a 3.5 M solution to make 100.0 mL

of solution, what is the molarity of the dilute solution?

.5fY . 0.o?°Lfy\ . O'

Practice: If you neeggQ,mL of 2.0 M H2SO4 and all you have is a

pure 18.0 M stock solution, how much initial volume of solvent

would you need?

O.D L

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Page 10 of 12 Unit 13 Notes

13.4 COLLIGATIVE PROPERTIES OF SOLUTIONS

What is a colligati e property? - a property of solutions that depends ONLY on

and NOT the

Jow\ h efI O IMI.I UI 1 y a

1 &

3re are 3 colligative properties of solutions:

l) )~ >geMase (o Mfl P r f e (Jf tDiagram - rl r

o o o <S>0 <& >

1

a - 0 (

./ ,, ;o O L. - O C3 3 c3

n

> 3 O

•

ExplanatT' . , _ I, I . ' f) ¦ ,/A,

5 t ff U 15• • +• l+ p Decrease in vapor pressure is proportional to I t v , r * :

sucrose 1 Darticle, o ial wi-

NaCl particles ( )

CaBr2 particles ( / OhJ ( )

t+ cr tt ,, ,«ls ** 1

¦ r f-(

wv&'S'e. [V '! fo (e Solutions of equal molarity of Kl at I MgF2 re compared. Which would have a lower vapor pressure and why?

I'.-t

Explanation:

,fir+-! 1 r

t

leJ.. vw f

sovii a\tf . C0 rt? 'Examples:

1 -( o - T i\4L

I

'

oA

Page 11 of 12Unit 13 Notes

Examples: 'l[6\/ <

f t/\ J _> \ :E ¦ «i -1 o ,i. .1; .. |'r ', | J' f i 1 i<~ '[ n,A u ' > ;ur-¦ I'1

[ - VI- \( ( ll ! 1 !-( Solutions of equal molarity of Kl and MgF2 are compared. Which would have a higher boiling point and why?

M+ 1 l/f* ,!r J>,:'1 '1 - f ' i /,, nf ji v $ *

Which would have a lower freezing point and why? i t ) ' ry .

* ' x -

ViiTyndall effect -I 1 ,r

Susoension- ttUV K Hi li

IP

Colloids - ( A'l' 1 x Z a.' ". i

/ ft A , . .1 -.5J'P& . \,s,f

«

l| _'1

) / /'{-/ ¦ f- 2 ' .ftft’; r .<'p,.; 'iComoarison: Solutions. Colloids, and Suspensions

iS x < l% A Ia I «' - - ,x j, J, j f7

l

•ysi

Property Solution Colloid Suspension

Uniformityi:1.

*

(llcfcl,

Solute particle type, '? (jmm ki4 id

: ' < ¦ ¦ " : M

€'J-aM I

Particle size //,,'! - 1 A/'A /- f & T' A.

Effect of light ftft; ;x

Effect of gravity f ftxr l irv tz

Filtration f'} I i ( F } f:kr\((,>) ' d V

1 1 *

Examples - , '|j fM lA. . '¦ A ¦'

i -\ i, • , ! ’ ,,

. 1 t 1 1

Unit 13

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Unit 13 Electronegativity

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Extra Credit Unit 13

Solutions 1 * 3

1 Depends only on the number of particles dissolved andnot the nature of the solute (two wo ds).

3 Two liquids that are able to dissolve into one another(i,e, water & alcohol),

7 Substance being dissolved an lesser in amount.8 Two liquids that are not able to dissolve into one

anothe (i.e oil & water).12 Solution that contains mo e solute th n it should be

able to hold at a constant temperature,14 Solution that contains a low concentration of solute.15 N mber of particles that dissolves in a given quantity

of a solven((usually 100g)at a given temperature toroduce a saturated solution.

17 ete ogeneous mixtu e fro which particles se a atean settle to the bottom of the container upon standing.

18 Compound that conducts an electric cur ent in solutionor in the molten state.

20 Heterogeneous mixtu es containing particles that aresmaller than suspensions and large th n true solutions,

21. Temperature at which tire vapor pressure of thesol tion is equal to the at os he ic p essure a o ndthe solution (t o wo ds).

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DOWN2 Way to predict If a substance ill issolve (three

word ),4 Solution that contains the maximum amount of solute .

for a given amo nt of solvent at a contant temperature'.5 Moles of sol te divided by Liters of solution.6 A sol tion that contains a high concentration of solu e.9 omogeneous clea solution of small particles an no

Tyndall Effect.10 Proce s that occurs when a solute dissolves into a >

solvent,11 Solution that contains less solute than a saturated

solution.13 Scatte ing of visible li ht in all di ections hen passed

th ough a solution (two words),16 Dissolving medium and g eater in a ount,1 Molecule that has one negative end and one positive

end.

Solutions

Unit 13 Electronegativity

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Periodic Table Unit 13

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