Equilibria Quiz

Question 1 of 22

1

Dynamic Equilibrium: A situation in which the ❌ of a constant ❌ reaction mixture does not ❌ because both forward and backward reactions are proceeding at the same ❌.

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composition

concentration

rate

change

Explanation

Question 2 of 22

1

Which of the following are conditions which apply to all equilibria?

Select one or more of the following:

Equilibrium can only be reached in a closed system.
Equilibrium can only be reached if the reaction starts from the reactants on the left of the equation.
Equilibrium is a dynamic process which is reached when the rates of two opposing simultaneous processes are the same.
Equilibrium has been reached when the amounts of products and reactants in the equilibrium mixture is the same.
You can tell that equilibrium has been reached when the macroscopic properties of the system do not change with time (i.e. density, concentration, colour and pressure)

Explanation

Question 3 of 22

1

Once equilibrium is reached the concentrations of the reactants and the products do not change.

Select one of the following:

True
False

Explanation

Question 4 of 22

1

What can be said about the rates of the forwards and backwards reactions when equilibrium has been reached?

Select one of the following:

They are equal and constant.
The rate of the reactions is zero as the reactions have stopped.
They are still changing.

Explanation

Question 5 of 22

1

A + B <---> C + D
At the ❌ of the reaction the forward rate is fast, because A and B are ❌. There is no ❌ because there is no C and D.
Then as the ❌ of C and D build up, the reverse reaction speeds up. At the same time the concentrations of A and B ❌ so the forward reaction ❌.
A point is reached where exactly the same ❌ are changing from A and B to C and D as are changing from C and D to A and B. ❌ has been reached.

NB. An equilibrium ❌ can have any proportions of reactants and products. The proportions may be changed depending on the ❌ of the reaction, such as temperature, ❌, and concentration. But at any given constant conditions the proportions of reactants and products ❌ change.

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start

plentiful

reverse reaction

concentrations

decrease

slows down

number of particles

Equilibrium

mixture

conditions

pressure

do not

Explanation

Question 6 of 22

1

Le Chatelier's Principle: For a closed system in dynamic equilibrium, if a change is made the equilibrium will shift to increase that change.

Select one of the following:

True
False

Explanation

Question 7 of 22

1

If you ❌ the concentration of one of the reactants, Le Chatelier's principle says that the ❌ will shift in the direction what tends to reduce the concentration of this reactant.
A(aq) + B(aq) <---> C(aq) + D(aq)
If you add some extra A (increase its ❌), the only way that the system can reduce the concentration of A is by ❌ it with B to form more C and D. So, adding more A uses up more B, ❌ more C and D, and moves the equilibrium to the ❌. You end up with a ❌ proportion of products in the reaction mixture than before.

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increase

concentration

reacting

produces

right

greater

equilibrium

Explanation

Question 8 of 22

1

Pressure changes only affect reactions involving ❌. Changing the overall pressure will only change the position of equilibrium of a gaseous reaction if there are a ❌ number of molecules on either side of the equation.

N204(g) <---> 2NO2
❌ the pressure of a gas means that there are more molecules of it in a given volume - it is equivalent to increasing the ❌ of a solution.
If you increase the pressure on this system, Le Chatelier's principle tells us that the position of equilibrium will move to ❌ the pressure. This meas it will more to the ❌ because fewer molecules exert less pressure.

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gases

different

Increasing

concentration

decrease

left

Explanation

Question 9 of 22

1

Increasing the pressure or decreasing the volume of a mixture of gases decreases the concentration of all the reactants and products by the same amount, not just one of them.

Select one of the following:

True
False

Explanation

Question 10 of 22

1

The rate at which equilibrium is reached will be speeded up by increasing the pressure, as there will be more collisions in a given time.

Select one of the following:

True
False

Explanation

Question 11 of 22

1

Increasing the temperature of a reaction will cause the equilibrium to shift in which direction?

Select one of the following:

To favour the endothermic reaction
To favour the exothermic reaction

Explanation

Question 12 of 22

1

What effect would adding a catalyst have on a reversible reaction in a closed system? (Choose TWO)

Select one or more of the following:

The position of equilibrium would shift to favour the forwards reaction.
The position of equilibrium would shift to favour the reverse reaction.
The position of equilibrium would not change.
Equilibrium would be reached faster.
The reaction would never reach equilibrium.

Explanation

Question 13 of 22

1

80% of ammonia produced is used to make which product?

Select one of the following:

Fertilisers
Synthetic fibers
Dyes
Explosives
Plastics

Explanation

Question 14 of 22

1

N2(g) + ❌H2(g) <---> ❌NH3(g) [delta H = -92kJmol^-1]

Almost all ammonia is made by the ❌ process, in which the reaction above is the key step. A low temperature and high ❌ would give close to 100% conversion whereas low pressure and high temperature would give almost no ❌. However, a compromise is used to ensure the rate of reaction is ❌ viable and the conditions safe. Most plants run at a pressure of around 20000kPa (c. ❌ atmospheres) and a temperature of about ❌K (c. 450 celsius).
The raw materials for the Haber process are air (providing the nitrogen), water, and natural gas (methane). These provide the hydrogen by the following reaction:
❌(g) + H2O(g) ---> ❌(g) + 3H2(g)
The nitrogen and hydrogen are fed into a converter in the ratio ❌ and passed over an ❌ catalyst.
The conversion is not at maximum as the conditions are not optimum (a ❌ is used) and the gases flow continuously over the catalyst so they do not spend long enough in contact with the catalyst to reach ❌. Any unconverted reactants are ❌ through the converter to increase the yield.

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3

2

Haber

pressure

ammonia

200

670

economically

CH4

CO

1:3

iron

compromise

equilibrium

recycled

Explanation

Question 15 of 22

1

The most common source of ethanol for industrial use is the fermentation of sugars such as glucose.

Select one of the following:

True
False

Explanation

Question 16 of 22

1

Fill the blank spaces to complete the text.

Ethanol is the alcohol in alcoholic drinks, but also has many uses for example making cosmetics, drugs, detergents, inks, and as a motor . At present the main source of ethanol for industrial use is from crude oil.
Ethanol is made by the hydration of ethene. The reaction is and is speeded up by a catalyst of acid absorbed on silica.
The equation is:
C2H4(g) + (g) <---> C2H5OH(g) [delta H = -46kJmol^-1]
Applying Le Chatelier's principle to this predicts the maximum yield will be produced with pressure, low temperature, and excess steam. However, there are practical problems: high pressure can cause ethene to polymerise; high pressure increases and danger; low temperature reduces the rate of reaction; too much steam dilutes the catalyst. Therefore in practise, conditions of about 570K and kPa are used. These give a conversion to ethanol of only around 5%, but the unreacted reactants are until about 95% conversion is obtained.

Explanation

Question 17 of 22

1

Le Chatelier's principle tells us that the methanol synthesis reaction will give the highest yield at low temperature and high pressure.

Select one of the following:

True
False

Explanation

Question 18 of 22

1

Which of the following is true?
The Kc of a reaction is...

Select one of the following:

[products]/[reactants]
[reactants]/[products]
([reactants]x[products])/2

Explanation

Question 19 of 22

1

Kc > 1 --> ❌
Kc = 1 --> ❌
Kc < 1 --> ❌

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equilibrium lies towards the products

equal concentrations

equilibrium lies towards the reactants

Explanation

Question 20 of 22

1

The equilibrium constant (Kc) does not change with concentration or pressure, but it does when the temperature is changed.

Select one of the following:

True
False

Explanation

Question 21 of 22

1

When can the number of moles of products and reactants be used to calculate the Kc instead of the concentrations?

Select one of the following:

When all the products and reactants have different powers/indicies.
When there is only one product.
When all the products and reactants have equal volume.

Explanation

Question 22 of 22

1

The Kc of the reaction between nitrogen monoxide (NO) and oxygen (O2) to form nitrogen dioxide (NO2) has no units.

Select one of the following:

True
False

	Created by Leah Firmstone about 7 years ago

A level Chemistry A level Quiz on Equilibria Quiz, created by Leah Firmstone on 02/26/2017.

Equilibria Quiz

Equilibria Quiz

Question 1 of 22

Dynamic Equilibrium: A situation in which the ❌ of a constant ❌ reaction mixture does not ❌ because both forward and backward reactions are proceeding at the same ❌.

Drag and drop to complete the text.

Explanation

Question 2 of 22

Which of the following are conditions which apply to all equilibria?

Select one or more of the following:

Explanation

Question 3 of 22

Once equilibrium is reached the concentrations of the reactants and the products do not change.

Select one of the following:

Explanation

Question 4 of 22

What can be said about the rates of the forwards and backwards reactions when equilibrium has been reached?

Select one of the following:

Explanation

Question 5 of 22

Drag and drop to complete the text.

Explanation

Question 6 of 22

Le Chatelier's Principle: For a closed system in dynamic equilibrium, if a change is made the equilibrium will shift to increase that change.

Select one of the following:

Explanation

Question 7 of 22

Drag and drop to complete the text.

Explanation

Question 8 of 22

Drag and drop to complete the text.

Explanation

Question 9 of 22

Increasing the pressure or decreasing the volume of a mixture of gases decreases the concentration of all the reactants and products by the same amount, not just one of them.

Select one of the following:

Explanation

Question 10 of 22

The rate at which equilibrium is reached will be speeded up by increasing the pressure, as there will be more collisions in a given time.

Select one of the following:

Explanation

Question 11 of 22

Increasing the temperature of a reaction will cause the equilibrium to shift in which direction?

Select one of the following:

Explanation

Question 12 of 22

What effect would adding a catalyst have on a reversible reaction in a closed system? (Choose TWO)

Select one or more of the following:

Explanation

Question 13 of 22

80% of ammonia produced is used to make which product?

Select one of the following:

Explanation

Question 14 of 22

Drag and drop to complete the text.

Explanation

Question 15 of 22

The most common source of ethanol for industrial use is the fermentation of sugars such as glucose.

Select one of the following:

Explanation

Question 16 of 22

Fill the blank spaces to complete the text.

Explanation

Question 17 of 22

Le Chatelier's principle tells us that the methanol synthesis reaction will give the highest yield at low temperature and high pressure.

Select one of the following:

Explanation

Question 18 of 22

Which of the following is true? The Kc of a reaction is...

Select one of the following:

Explanation

Question 19 of 22

Kc > 1 --> ❌ Kc = 1 --> ❌ Kc < 1 --> ❌

Drag and drop to complete the text.

Explanation

Question 20 of 22

The equilibrium constant (Kc) does not change with concentration or pressure, but it does when the temperature is changed.

Select one of the following:

Explanation

Question 21 of 22

When can the number of moles of products and reactants be used to calculate the Kc instead of the concentrations?

Which of the following is true?
The Kc of a reaction is...

Kc > 1 --> ❌
Kc = 1 --> ❌
Kc < 1 --> ❌