Chemistry

pH = -log [H+] pOH = -log [OH-] 14.00 = pH + pOH

[H+] = antilog(pH) or 10-pH [OH-] = antilog(pOH) or 10-pOH Kw = [H+][OH–]= 1.0 x 10-14

pKa = -log(Ka) Kw = Ka Kb for conj. pair

Weak acids in water: Ka = [H+][A-] / [HA]init Weak bases in water: Kb = [-OH] [BaseH] /[Base]init % ionization = [H+] / [HA]init x 100 % % ionization = [A-] / [HA]init x 100 %

 

ΔSreaction° = SmS° (products) – SnS° (reactants) Units: J / (mole . K) ΔG = ΔH – TΔS

Practice Exam Section: Please show all work for full credit on this assignment.

 

1. Rank in order of increasing acidity: (Note: the end of a line represents a Carbon atom)

a. b.

 

 

c. HF

 

 

 

2. a. Define pH and pOH

b. Write equations for converting pH and [H+]

c. Write equations for converting pOH and [OH-]

d. Write the equation relating pH and pOH

e. Write the equation for relating Kw to the hydroxide/hydrogen ions.

 

 

3. Complete the table below

pH

pOH

[H+]

[OH-]

Acidic/Basic/Neutral

9.68

8.90

7.8 x 10-5
1.1 x 10-13

 

13.1

8.07

4. What is the pH of a 0.075 M solution of hydroiodic acid, HI?

 

5. Calculate the pH for each of the following

a. 0.60 M HNO2, Ka = 4.0 10–4. b. 0.16 M solution of HOCl, Ka = 3.5 10–8.

 

 

6. Calculate the pH for each of the following weak bases.

a. 0.570 M solution of aniline, Kb = 7.4 × 10-10 b. 0.380 M solution of ethylamine, Kb = 4.3 × 10-4

 

 

 

7. Predict whether the following salts will from a solution that is acidic, basic or neutral.

a. FeCl3 e. NaF b. NH4ClO f. LiClO4 c. K2CO3

 

8. Calculate the Ka value for a 1.0 M solution of a weak acid that is

a. 5.0% ionized b. 0.50 % ionized c. 20. % ionized

 

 

 

9. Select which of the following will produce a buffered solution.

a) 100 mL of 0.1 M Na2CO3 and 50 mL of 0.1 M HCl

b) 100 mL of 0.1 M NaHCO3 and 25 mL of 0.2 M HCl

c) 100 mL of 0.1 M Na2CO3 and 75 mL of 0.2 M HCl

d) 50 mL of 0.2 M Na2CO3 and 5 mL of 1.0 M HCl

e) 100 mL of 0.1 M Na2CO3 and 50 mL of 0.1 M NaOH

 

10. Calculate the pH in a 2.0-liter buffered solution that is 0.82 M NH3 (Kb = 1.8 x10–5) and 0.26 M NH4F.

 

 

 

 

11. Calculate the pH of a 1.00 M acetic acid (Ka = 1.8 x 10–5) after adding 0.0040 M NaOH.

 

12. Calculate the pH after adding 0.30 L of 0.020 M KOH to a 1.0-liter solution containing 0.25 M HF and
0.66 M NaF (Ka for HF is 7.2 10–4).

 

 

 

13. What is the molarity of a sodium hydroxide solution if 27.9 mL of this solution reacts exactly with 22.30
mL of 0.253 M sulfuric acid?
14. Calculate the pH if 25 mL of 0.750 M HCl are titrated with 100. mL of 0.346 M NaOH.

 

15. Calculate Ksp if the solubility of CaSO4 in pure water at 0oC is 1.13 gram(s) per liter.
16. Silver chromate, Ag2CrO4, has a Ksp of 9.00 x 10–12. Calculate the solubility in mol/L of silver chromate.

17. ΔS° for the following reaction is -258.2 J/mol∙ K. Calculate S° for C3H4.

C3H4(g) + 2 H2(g) → C3H8(g)

S° 130.6 269.9 J/mol∙deg

 

18. Indicate if entropy will increase or decrease.

a) precipitation

b) gaseous reactants forming a liquid

c) a burning piece of wood

d) melting ice

e) evaporation of 1 mol of CCl4(l)

f) mixing 5 mL ethanol with 25 mL water

g) compressing 1 mol Ne at constant temperature from 1.5 L to 0.5 L

h) raising the temperature of 100 g Cu from 275 K to 295 K

i) grinding a large crystal of KCl to powder

 

19. Calculate ΔG° at 25°C for N2O4(g) → 2 NO2(g) ΔH° = 58.03 kJ ΔS° = 176.7 J/K

 

 

20. Calculate ΔS°rxn or the reaction, CaCO3(s) → CaO(s) + CO2(g)
S° (J/mol K) 88.70 39.75 213.6

 

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