Exam 3

Le Châtlier's

100

Which is the correct equilibrium constant expression for the rxn: 

Fe2O3(s) + 3H2(g) ⇋ 2Fe(s) + 3H2O(g)k

Kc = [H2O]3 / [H2]3

200

 Calculate Kp for the reaction 2NOCl(g) ⇋ 2NO(g) + Cl2(g) at 400°C if Kc at 400°C for this reaction is 2.1 x 10–2

1.2

300

1. Consider the two gaseous equilibria
   2SO2(g) + O2(g) → 2SO3(g) K1 

2SO3(g) →2 SO2(g) + O2(g) K2
The values of the equilibrium constants K1 and K2 are related by 

K2 = 1/K1

400

Consider the reaction A(g) ⇋ 2 B(g) where Kp = 5.0 at 25 °C. If 0.50 mol A and 2.0 mol B are introduced into a 1.0 L flask at 25 °C, what change in concentrations (if any) will occur in time?

[A] will increase and [B] will decrease

500

1. The following reactions occur at 500 K. Arrange them in order of increasing tendency to proceed to completion (least completion to greatest completion). 

1)2NOCl→2NO+Cl2    Kp =1.7x10^–2

2) N2O4 → 2NO2        Kp = 1.5x10³

3)2SO3 → 2SO2 +O2      Kp =1.3x10^–5

4)2NO2 → 2NO+O2    Kp =5.9x10^–5 

3,4,1,2

Acids and Bases

100

Calculate the hydrogen ion concentration in a solution of iced tea with lemon having a pH of 2.87.

1.3*10^-3

200

Acid strength decreases in the series HI > HSO4– > HF > HCN. Which of these species is the weakest base?

I–

300

Identify the conjugate base of HPO₄^2– in the reaction

        HCO^-₃ + HPO₄^-2  ->  H₂CO₃ + PO₄^3–

PO4^-3

400

Which of the following yields an acidic solution when dissolved in water?

A) HNO2 B) LiOH C) KClO2 D) NaCl E) Ca(OH)2

HNO2

500

List strong acids and strong bases.

HCl, HBr, HI, HNO3, HClO3, HCLO4, H2SO4

LiOH, NaOH, KOH, RbOH, CsOH, Sr(OH)2, Ba(OH)2

Buffer

100

Acid strength increases in the series: HCN < HF < HSO4–. Which of these species is the strongest base?

CN–

200

Calculate the pH of a buffer solution prepared by dissolving 0.20 moles of hydrocyanic acid and 0.80 moles of sodium cyanide in enough water to make 1.0 liter of solution.

Ka of HCN= 2.0 x 10 ^-4

pH=4.30

300

A 0.14 M HNO2 solution is 5.7% ionized. Calculate the H+ ion concentration.

8.0 x10–3 M

400

Calculate the pH of a buffer solution of 0.25M benzoic acid (C6H5CO2H) and 0.15M sodium benzoate (C6H5COONa) Ka = 6.5 x 10 ^-5 for benzoic acid.

3.97

500

You are asked to go into the lab and prepare an acetic acid-sodium acetate buffer solution with a pH of 4. What molar ratio of acetic acid to sodium acetate should be used? Ka= 1.8 x 10 ^-5

a. 0.18 b. 0.84 c. 1.19 d. 5.50 e. 0.10

5.50 or .18

Titrations

100

A 40 mL sample of .1M acetic acid (pKa=4.76) is titrated with.15M sodium hydroxide.

Calculate the pH when 0.0 mL of sodium hydroxide are added to the solution.

2.8

200

From the previous question, Calculate the pH when 20mL of sodium hydroxide are added to the solution.

5.2

300

What is the pH at the equivalence point in the titration of 100mL of a 0.10M HCN (Ka= 4.9x10^-10) with 0.10M NaOH?

11

400

 In which one of the following solutions will acetic acid have the greatest percent ionization? 

A)  0.1 M CH3COOH 

B)  0.1 M CH3COOH dissolved in 1.0 M HCl 

C)  0.1 M CH3COOH plus 0.1 M CH3COONa 

D)  0.1 M CH3COOH plus 0.2 M CH3COONa 

 A

500

If 100mL of 0.30M sodium hydrogen carbonate is mixed thoroughly with 100mL of 0.10M sodium hydroxide, what is the pH when the pka of hydrogen carbonate is 10.3?

10

Miscellaneous

100

Best qb in the nfl?

Patrick Mahomes

200

Who created the national anthem?

Lana del Rey

300

Who was in Paris?

The peer leader Paris

400

This person was awarded two similar-looking towers in NYC in a particular day in September 2001

Osama Bin Laden

500

What is my favorite yearning song?

The one that got away by Katy Perry