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Chemical Equilibrium

Total questions: 37

Worksheet time: 38mins

Name
Class
Date
1.
2A + 3B  <---->  2AB
The forward reaction forms the substance __________.
a)
A
b)
B
c)
AB
d)
A + B
2.
2A + 3B  <---->  2AB
The reverse reaction points towards the __________.
a)
left
b)
right
c)
up
d)
down
3.
What are the two factors to look for when determining if the reaction is at equilibrium?
a)
Forward reaction rate is faster than the reverse and concentrations are equal
b)
Forward and reverse reaction rates are equal and concentration is conctant
c)
Forward and revers reaction rates are equal and concentration is equal
d)
Forward reaction rate is faster than the reverse and concentration is equal
4.
This symbol indicates that a reaction is ____________
a)
reversible
b)
irreversible
5.
At what time the reaction reached equilibrium?
a)
t1
b)
t2
c)
t3
d)
t4
6.
Which of the following is NOT true at equilibrium?
a)
The forward and reverse reactions proceed at the same rate.
b)
The concentrations of reactants and products do not change.
c)
The concentration of the reactants is equal to the concentration of the products.
d)
The forward and reverse reactions continue to occur.
7.
If a reaction is reversible and has reached equilibrium, what can be said about the amounts of reactants and products?
a)
some reactant, some product
b)
no reactant, all product
c)
all reactant, no product
8.

A complete reaction is in which:

a)

All the reactants convert into products

b)

All the reactants do not convert into products

c)

Half reactants convert into products

d)

only 10% reactants convert into products

9.
2SO2(g)+O2(g)⇌2SO3(g)
Removing O2(g) will
a)
shift equilibrium right
b)
shift equilibrium left
c)
decrease temperature
d)
have no change
10.
2SO2(g)+O2(g)⇌2SO3(g)
Adding SO2(g) will
a)
shift equilibrium right
b)
shift equilibrium left
c)
increase rate of reaction
d)
have no change
11.
Changes in pressure will only affect substances that are in the __________ state.
a)
gaseous
b)
liquid
c)
solid
d)
plasma
12.
What is the equilibrium-constant expression for 
CO2(g) + H2(g) ↔ CO(g) + H2O(l)
a)
Kc= [CO][H2O] / [CO2][H2]  
b)
Kc= [CO2][H2] / [CO]
c)
Kc= [CO2][H2] / [CO][H2O]
d)
Kc= [CO] / [CO2][H2]  
13.
2SO2(g)+O2(g)⇌2SO3(g)
Decreasing volume of container will
a)
shift equilibrium right
b)
shift equilibrium left
c)
change K
d)
have no change
14.

H2(g)+Cl2(g)⇌2HCl(g)

Increasing the pressure will

a)

shift equilibrium right

b)

shift equilibrium left

c)

You cannot predict the effect

d)

have no change

15.

H2(g)+Cl2(g)⇌2HCl(g)

The forward reaction is exothermic. What will happen to the equilibrium if the temperature is increased?

a)

equilibrium shifts right

b)

equilibrium shifts left

c)

You cannot predict the effect

d)

no change

16.

What kind of equilibrium does the reaction below show?

H2(g) +I2(g) ↔ 2HI(g)

a)

Heterogeneous equilibrium, all the reactants and products are in the same physical state.

b)

Homogeneous equilibrium, all the reactants and products are in the same physical state.

c)

Heterogeneous equilibrium, the reactants and products are present in more than one physical state

d)

Homogeneous equilibrium, the reactants and products are present in more than one physical state

17.
For the reaction...
heat  +  N2  +  O2  <−>  2NO
If the heat is removed from the chemical system, the concentration of N2 will _______.
a)
increase
b)
decrease
c)
remain the same
d)
double
18.

An equilibrium constant with a value of 4.6 x 1015 indicates that at equilibrium

a)

the reactants are favored.

b)

the products are favored.

c)

approximately equal concentrations of reactants and products are present.

19.

When pressure decreases, in which direction does the equilibrium shift?

a)

The equilibrium shifts in the direction that increases the number of moles of gas.

b)

The equilibrium shifts in the direction that decreases the number of moles of gas.

c)

The equilibrium does not shift.

d)

The equilibrium shifts always shifts to the right.

e)

The equilibrium shifts always shifts to the left.

20.

For an endothermic reaction, increasing the temperature

a)

does not shift the equilibrium since K is a constant.

b)

increases the rate of the reverse reaction to form more reactants.

c)

increases the rate of the forward reaction to form more products.

d)

increases the rate of the reverse reaction to form more products.

21.

What is the value for Kc if [CO] = 0.025, [H2] = 0.013 and [CH3OH] = 0.0028 for the following reaction?

CH3OH(g) ⇌ CO(g) + 2 H2(g)

a)

0.12

b)

9.1 × 10-7

c)

6.6 × 102

d)

1.5 × 10-3

e)

8.6

22.

For the reaction PCl5 (g) → PCl3 (g) + Cl2 (g) Kc = 0.0454 at 261°C. If a vessel is filled with these gases such that the initial concentrations are [PCl5] = 0.25M, [PCl3] = 0.20 M, and [Cl2] = 2.25 M, in which direction will a reaction occur and why?

a)

toward products because Q = 0.56

b)

toward reactants because Q = 1.8

c)

it is at equilibrium

d)

toward reactants because Q = 0.0454

e)

toward products because Q = 2.8

23.

Consider the following reaction.

C(s) + H2O(g) ⇌ CO(g) + H2(g)

At equilibrium at a certain temperature, [H2O(g)] = 0.12 M, and [CO(g)] = [H2(g)] = 1.2 M. If suddenly these concentrations are increased by 0.50 M, which of the following is true?

a)

Since Kc does not change, nothing happens.

b)

more products are formed

c)

more H2O(g) will be formed

d)

Kc = 4.66

24.

For the reaction: CH4(g) + 2 H2O(g) ⇔ CO2(g) + 4 H2(g) ΔH° = +190 kJ raise the temperature to 1200 K:

a)

the temperature increases.

b)

the ΔH° increases.

c)

the reaction reacts to the right.

d)

the reaction reacts to the left.

e)

there is no change.

25.

Consider the reaction: CH4(g) + 4 Cl2(g) ⇔ CCl4(l) + 4 HCl(g) ΔH° -398 kJ/mol The equilibrium is displaced to the right if:

a)

the pressure is lowered

b)

the temperature is raised

c)

some hydrogen chloride is added

d)

some hydrochloric acid is removed

26.

Choose the correct statement about a container in which the chemical equilibrium is established:

2 SO2(g) + O2(g) → 2 SO3(g) + heat

a)

A decrease in the volume will decrease the amount of SO2 present.

b)

An increase in amount of O2 will increase the amount of SO2 present.

c)

A decrease in temperature will increase the amount of SO2 present.

d)

A decrease in the amount of SO3 present will increase the amount of SO2 present.

e)

A decrease in amount of O2 will decrease the amount of SO2 present.

27.

For a reaction Keq = 1.2 × 10-6 at T = 200 K. What is ΔG° for the reaction?

a)

-22.7 kJ/mol

b)

22.7 kJ/mol

c)

53.6 kJ/mol

d)

170 kJ/mol

e)

-53.6 kJ/mol

28.

Calculate the temperature for which Keq for a reaction is 1.04 × 103 where ΔH° = -83.2 kJ/mol and ΔS° = -246 J/mol ∙ K.

a)

0.307 K

b)

307 K

c)

274 K

d)

0.274 K

e)

cannot be determined without ΔG°

29.

Given N2 (g) + 3 H2 (g) ⇌ 2 NH3 (g), which scenario will allow you to eventually reach an equilibrium mixture involving these chemicals?

a)

Place only N2 into a sealed vessel.

b)

Place only H2 into a sealed vessel.

c)

Place only NH3 into a sealed vessel.

d)

none of the above

30.

Le Chatelier's Principle states that:

a)

a disturbing force must be applied to a system in order for it to reach equilibrium.

b)

when a system at equilibrium is disturbed, a new equilibrium constant is established.

c)

when a chemical system at equilibrium is disturbed, the system shifts in order to minimize the effect.

d)

when a chemical system is at equilibrium it is no longer possible to alter the system.

31.

What is the equilibrium expression for:

Fe3O4(s) + 4H2(g) <=> 3Fe(s) + 4H2O(g)

Kc =

a)

[Fe]3 [H2O]4 / [Fe3O4] [H2]4

b)

[Fe3O4] [H2]4 / [Fe]3 [H2O]4

c)

[H2O]4 / [H2]4

d)

[Fe] [H2O] / [Fe3O4] [H2]

32.

A catalyst is added to a system at equilibrium.

The concentration of the reactants will then

a)

decrease


b)

increase


c)

remain the same

d)

approach zero

e)

none of the above

33.

A solution at equilibrium must be

a)

concentrated

b)

saturated

c)

unsaturated

d)

diluted

34.

If QC > KC , in order to achieve chemical equilibrium, the reaction shift to the

a)

Left

b)

Right

35.

Given the Kc for a forward reaction, how can you find Kc for the reverse reaction?

a)

Divide Kc by 1

b)

Divide 1 by Kc

c)

Square Kc

d)

Take the square root of Kc

36.
Why is equilibrium called a dynamic state?
a)
Chemists try to convert as much reactants as possible into products.
b)
The reactions at equilibrium continue to take place once equilibrium is established.
c)
The products of a forward reaction are favored, so equilibrium lies to the right.
d)
All chemical reactions are considered to be reversible under suitable conditions.
37.
The picture shows a reversible chemical reaction taking place. How can equilibrium be reached?
a)
Stopper the flask.
b)
Add more reactants.
c)
Add more products.
d)
Cool the contents.