solutions. composition solute solvent dilute concentrated

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Page 1: Solutions. Composition solute solvent dilute concentrated

Solutions

Page 2: Solutions. Composition solute solvent dilute concentrated

Composition

solutesolventdilute

concentrated

Page 3: Solutions. Composition solute solvent dilute concentrated

Composition

Molarity (M)—

the number of moles ofsolute per liter ofsolutionmol/L

Page 4: Solutions. Composition solute solvent dilute concentrated

Composition

Mass percent—

the mass of solute permass of solution x 100unit-less

Page 5: Solutions. Composition solute solvent dilute concentrated

Composition

Mole fraction ()—

the moles of solute pertotal moles of solution(solute) or the moles ofsolvent per total molesof solution (solvent)

Page 6: Solutions. Composition solute solvent dilute concentrated

Composition

Molality (m)—

the moles of solute perkilogram of solvent

mol/kg

Page 7: Solutions. Composition solute solvent dilute concentrated

Composition

Normality (N)—

the equivalents of soluteper liter of solution

eq/L

Page 8: Solutions. Composition solute solvent dilute concentrated

Composition

Equivalent—

the mass of an acid orbase that can furnish orreact with 1 mole ofprotons

Page 9: Solutions. Composition solute solvent dilute concentrated

Composition

Equivalent—

the mass of an oxidizingor reducing agent thatcan accept or furnish 1mole of electrons

Page 10: Solutions. Composition solute solvent dilute concentrated

Composition Practice

Mylanta® Liquid contains200mg of aluminumhydroxide for every 5mLof solution.

Page 11: Solutions. Composition solute solvent dilute concentrated

Composition Practice

1. Assuming that thealuminum hydroxide isthe only ingredient,what is the molarity ofthe solution?

Page 12: Solutions. Composition solute solvent dilute concentrated

Composition Practice

2. Assuming that thedensity of the solutionis 1g/mL, what is themass percent of thesolution?

Page 13: Solutions. Composition solute solvent dilute concentrated

Composition Practice

3. Assuming that themass of water is4800mg, what are themole fractions of boththe solute and thesolvent?

Page 14: Solutions. Composition solute solvent dilute concentrated

Composition Practice

4. What is the molalityof the solution?

5.What is the normality of thesolution?

Page 15: Solutions. Composition solute solvent dilute concentrated

1. 0.513 mol/L2. 4% (mass)3. 0.00953 = solute

0.990 = solvent

4. 0.534 mol/kg5. 1.538 eq/L

Page 16: Solutions. Composition solute solvent dilute concentrated

Energy of Solution Formation“like dissolves like”

due to the energy associated with the formation of a solutionStep 1: solute expands (endo)Step 2: solvent expands (endo)Step 3: solute and solvent

interact (usually exo)

Page 17: Solutions. Composition solute solvent dilute concentrated

Energy of Solution Formation

sum of steps 1-3 gives theenthalpy of solution, or heatof solution (Hsoln)

Hsoln= H1 + H2 + H3

Page 18: Solutions. Composition solute solvent dilute concentrated

Energy of Solution Formation

Consider mixing oil and water…They are immiscible.Oil molecules are large andhave LDF…thus, H1 will belarge and positive for theoil expansion

Page 19: Solutions. Composition solute solvent dilute concentrated

Energy of Solution Formation

Water molecules haveH-bonds…thus, H2 will belarge and positive for thewater expansion

Page 20: Solutions. Composition solute solvent dilute concentrated

Energy of Solution Formation

H3 will be small sincenonpolar and polar moleculestend to have no attractiveforces

Page 21: Solutions. Composition solute solvent dilute concentrated

Energy of Solution FormationHsoln will be large and positivebecause of the large impactthat H1 and H2 have.

Thus, it would require a largeamount of energy for the oiland water to mix

Page 22: Solutions. Composition solute solvent dilute concentrated

Energy of Solution Formation

Consider mixing NaCl andwater… They are soluble.NaCl formula units havestrong ionic forces…thus,H1 will be large and positivefor the NaCl expansion

Page 23: Solutions. Composition solute solvent dilute concentrated

Energy of Solution Formation

Again, water molecules haveH-bonds…thus, H2 will belarge and positive for thewater expansion

Page 24: Solutions. Composition solute solvent dilute concentrated

Energy of Solution Formation

H3 will be large andnegative since the attractiveforces between the ions andthe polar water moleculesare so strong

Page 25: Solutions. Composition solute solvent dilute concentrated

Energy of Solution Formation

The Hsoln for NaCl in water is actually 3 kJ/mol. It ispositive and small…and it ismore disordered than theoriginal NaCl and water…hence, favorable.

Page 26: Solutions. Composition solute solvent dilute concentrated

Solubility

•the amount of solute that dissolves in solvent

Page 27: Solutions. Composition solute solvent dilute concentrated

Factors Affecting Solubility

•Structure•Pressure•Temperature

Page 28: Solutions. Composition solute solvent dilute concentrated

Structure’s Effect

•A, D, E, & K are fat-soluble because nonpolar, long H-C chains (hydrophobic)

•B & C are water-soluble because they have polar

0-H and C-O bonds (hydrophilic)

Page 29: Solutions. Composition solute solvent dilute concentrated

Pressure’s Effect

•Gas in a liquid•Increased pressure above a liquid means increased solubility of a gas in the liquid…Henry’s Law

Page 30: Solutions. Composition solute solvent dilute concentrated

Henry’s Law

•Amount of a gas dissolved in solution is directly proportional to the pressure of the gas above the solution.

Page 31: Solutions. Composition solute solvent dilute concentrated

Henry’s Law•P = kC

•S1 = S2

P1 P2

•Obeyed particularly well in non-dissociated solutions

Page 32: Solutions. Composition solute solvent dilute concentrated

Temperature’s Effect•Most solids’ solubilities will increase as temperature is increased…but not all

•Must be determined by experimentation

Page 33: Solutions. Composition solute solvent dilute concentrated

Temperature’s Effect

Na2SO4

Na2SO

4

Page 34: Solutions. Composition solute solvent dilute concentrated

Temperature’s Effect•Gases’ solubilities will decrease as temperature is increased

•Thermal pollution

Page 35: Solutions. Composition solute solvent dilute concentrated

Lake Nyos, Cameroon

Page 36: Solutions. Composition solute solvent dilute concentrated

Lake Nyos, Cameroon

•August 21, 1986•>1700 people and >3000 cattle killed

•Lake turn-over thought to have been caused by volcanic activity

Page 37: Solutions. Composition solute solvent dilute concentrated

Lake Nyos, Cameroon

Page 38: Solutions. Composition solute solvent dilute concentrated

Vapor Pressure

•decreases with the addition of a nonvolatile solute to a solvent

•François Raoult studied the effects of a solute on vapor pressure

Page 39: Solutions. Composition solute solvent dilute concentrated

Raoult’s Law

•Psoln = (Posolvent)

(solvent)

•Linear relationship• y = mx + b

•b is zero

Page 40: Solutions. Composition solute solvent dilute concentrated

Raoult’s Law

•Psoln is the vapor pressure of the solution

•Posolvent is the vapor

pressure of the pure solvent

solvent is the mole fraction of the solvent

Page 41: Solutions. Composition solute solvent dilute concentrated

Raoult’s Law

•For volatile solutions,

•Ptotal = (PoA)(A) + (Po

B)(B)

Page 42: Solutions. Composition solute solvent dilute concentrated

Raoult’s Law•is to solutions what the ideal gas law is to gases

•Strong solute-solvent attraction results in a vapor pressure lower than what Raoult’s Law predicts

Page 43: Solutions. Composition solute solvent dilute concentrated

6. A carbonated beverage is bottled at 25°C with 5.00atm over the CO2 in the liquid. Assuming that the partial pressure of the CO2 in the atmosphere is

Page 44: Solutions. Composition solute solvent dilute concentrated

0.0004atm, calculate theequilibrium concentrations of CO2 before and after the bottle is opened. TheHenry’s Law constant forCO2 is 32Latm/mol at25°C

Page 45: Solutions. Composition solute solvent dilute concentrated

7. A solution was prepared by adding 20.0g of urea to 125g water at 25°C, the temperature at which water’s vapor pressure is 23.76torr. The

Page 46: Solutions. Composition solute solvent dilute concentrated

observed vapor pressureof the solution was

foundto be 22.67torr. What is the molar mass of urea?

Page 47: Solutions. Composition solute solvent dilute concentrated

8. A solution is prepared by mixing 5.81g acetone (C3H6O) and 11.9g chloroform (CHCl3). At 35°C this solution has a total vapor pressure of 260torr.

Page 48: Solutions. Composition solute solvent dilute concentrated

Is this an ideal solution?The vapor pressures ofpure acetone andchloroform at 35°C are345 and 293torr,respectively.

Page 49: Solutions. Composition solute solvent dilute concentrated

6.The unopened bottle’s CO2 concentration is 0.160 mol/L. The opened bottle’s concentration is 1.2 x 10-5 mol/L. That’s why it tastes flat.

Page 50: Solutions. Composition solute solvent dilute concentrated

7. The molar mass of urea is 59.7 g/mol.

8. The expected Ptotal is 319torr. Since Ptotal is actually 260torr, the solution does not behave ideally.

Page 51: Solutions. Composition solute solvent dilute concentrated

Colligative Properties•are dependent upon the number of solute particles dissolved in solution–Boiling point–Freezing point–Osmotic pressure

Page 52: Solutions. Composition solute solvent dilute concentrated

Boiling Point•is the temperature at which a substance’s vapor pressure equals the atmospheric pressure

•What effect does the addition of a nonvolatile solute have on vapor pressure?

Page 53: Solutions. Composition solute solvent dilute concentrated

Boiling Point•Thus, the boiling point of a solvent is elevated when a nonvolatile solute is added.

•The amount by which it increases is calculated by…

Tb = kbmsolutei

Page 54: Solutions. Composition solute solvent dilute concentrated

Boiling PointTb is the change in boiling point of the solution

•kb is the boiling point constant for the solvent

•msolute is the molality of the solute

•i is the van’t Hoff factor

Page 55: Solutions. Composition solute solvent dilute concentrated

Boiling Point

•van’t Hoff factor–the number of particles of dissolved solute per mole of solute…in other words, the number of dissociated particles

Page 56: Solutions. Composition solute solvent dilute concentrated

Boiling Point

•Know the boiling and point constant for water…

kb = 0.512°Ckg/mol

Page 57: Solutions. Composition solute solvent dilute concentrated

Freezing Point•is the temperature at which a solid’s vapor pressure equals its liquid’s vapor pressure

•A nonvolatile solute will lower the vapor pressure of the liquid.

Page 58: Solutions. Composition solute solvent dilute concentrated

Freezing Point•As the solution is cooled the vapor pressure of the pure solid decreases more rapidly than the vapor pressure of the pure liquid.

•Thus, the freezing point will be lowered.

Page 59: Solutions. Composition solute solvent dilute concentrated

Freezing Point

Tf = kfmsolutei

•Know the freezing point constant for water…

kf = 1.86°Ckg/mol

Page 60: Solutions. Composition solute solvent dilute concentrated

Osmotic Pressure•is the pressure needed to stop osmosis from occurring

•may be calculated using

= MRTi

Page 61: Solutions. Composition solute solvent dilute concentrated

Osmotic Presure is the osmotic pressure•M is the molarity of the solution

•R is the gas law constant, 0.08206 Latm/Kmol

•T is the Kelvin temperature

Page 62: Solutions. Composition solute solvent dilute concentrated

Osmotic Presure•When pressure greater than is applied, reverse osmosis will occur–Solute particles are filtered out

–Desalination is an example

Page 63: Solutions. Composition solute solvent dilute concentrated

•Isotonic solutions–same osmotic pressure

•Hypertonic solutions–migration of solvent out of cells results in crenation

•Hypotonic solutions–migration of solvent into cells results in hemolysis

Page 64: Solutions. Composition solute solvent dilute concentrated

9. My car’s cooling system contains 2.51kg of water and 2.45kg of ethylene glycol (antifreeze), C2H6O2. Below what temperature will my engine block freeze?

Page 65: Solutions. Composition solute solvent dilute concentrated

10. If I were to substitute the ethylene glycol with sodium chloride, below what temperature will my engine block freeze?

Page 66: Solutions. Composition solute solvent dilute concentrated

11. When 10.0g of camphor are added to 100g of benzene, To

b is 80.1°C and kb is 2.53 °Ckg/mol, the boiling point of the solution is 81.76°C. What is the molar mass of the camphor?

Page 67: Solutions. Composition solute solvent dilute concentrated

12. A 20.0-mg sample of a protein is dissolved in water to make 25.0mL of solution. The osmotic pressure of the solution is 0.56torr at 25°C. What is the molar mass of the protein?

Page 68: Solutions. Composition solute solvent dilute concentrated

9. -29.2 °C10. -62.1 °C11. 152g/mol12. 26550g/mol