Chem 30 Unit D Review

Dynamic Equilibrium

100

Name three stressors that can be applied to an equilibrium system

1) Temperature

2) Concentration

3) Pressure/Volume

200

Write the Equilibrium Law expression for the following equation 

Zn(s) + Cu²⁺(aq)  ↔  Cu(s)  +  Zn²⁺(aq)

Kc = Zn²⁺(aq) / Cu²⁺(aq)

300

Draw the equilbrium expression for the following:

2H₂(g)  + O₂(g)  ↔  2H₂O (l)

[H_2]²[O_2]

_{H2O (l)  is a liquid and not part of this equilibrium expression.}

400

In the following system:  
N₂(g)  + 3H₂(g)   ↔  2NH₃(g) 

0.249 mol/L of N₂(g),  3.21 X 10^-2  mol/L of  H₂(g) and 6.42 X 10^-4 mol/L of NH₃(g) are combined in a 1.00 L vessel at 375°C.

What is the K_c value for the reaction and are the products or reactants favored?

0.0500

Reactants are favored since 0.05 < 1
(Ignore the temperature.)

500

C

ICE Tables

100

What does ICE stand for?

Initial, Change, Equilibrium

200

Consider the reaction for the decomposition of hydrogen iodine at 448°C. The initial concentration of HI(g) was 1.00x10^-3 mol/L. Once an equilibrium was established, the concentration of HI(g) was measured to be 0.078x10^-3 mol/L. Calculate the equilibrium constant (K_c)

2HI(g) < --> H₂(g) + I₂(g) 

8.73

300

In a 500 mL stainless steel reaction vessel at 900°C, carbon monoxide and water vapour react to produce carbon dioxide and hydrogen. Evidence indicates that this reaction establishes an equilibrium with only partial conversion of reactants to products. Initially, 2.00 mol of each reactant is placed in the vessel. The K_C for this reaction is 4.20 at 900°C. What will be the concentration of each substance at equilibrium?

CO(g)  +  H₂O(g)   ↔   CO₂ (g)   +  H₂ (g)

CO(g) & H₂O(g): 1.31mol/L

CO₂(g) & H₂(g): 2.69mol/L

400

If a 100 mL sample of 0.344 mol/L unknown acid has a pH of 4.1 at 30 degrees, then the Ka is?

Ka = 1.8 x 10^-8

500

A student measures the pH of a 0.25 mol/L solution of carbonic acid to be 3.48. Calculate the Ka for carbonic acid from this evidence

Ka = 4.39x10^-7

Bronsted-Lowry & Arrhenius

100

What is the Bronsted-Lowry definition of an acid and a base?

Acid: proton donor

Base proton acceptor

200

Identify the bases in the following chemical equation

HSO4- (aq) + HPO4^2- (aq) <--> H2PO4- (aq) + SO4^2- (aq)

HPO4^2-

SO4^2-

300

Identify the conjugate acid base pairs from the following reaction

HCO₃^- (aq)  +  CN^- (aq)  < -- > CO₃^2- (aq) +  HCN (aq)

1. HCO₃^-(aq) & CO₃^2-(aq) 

2. CN^-(aq) & HCN(aq)

400

What will be the predominant reaction if nitric acid is mixed with potassium fluoride 

H₃O⁺(aq)  +  F^-(aq) --> H₂O(l) + HF(aq)

Le Chatelier's Principle

100

True or false: According to Le Chatelier's Principle, when a stressor is applied to a a system at equilibrium, the system will shift to oppose the change until a new equilibrium is established.

True

200

If the concentration of HF(g) increased, which direction would the equilibrium shift and would this produce more or less product? 

CCl4(l) + 2HF(g) <--> CCl2F2(g) + 2HCl(g)

Equilibrium would shift right and more product would be produced

300

If the pressure of this system increased, which direction would the equilibrium shift?

2SO2(g) + O2(g) <--> 2 SO3(g)

right

400

If the volume of this system decreased, which direction would the equilibrium shift?

H₂(g) + Cl2(g) < -- > 2HCl(g)

The equilibrium would not shift