Catalysts

Hydrogen peroxide solution, H₂O₂(aq), decomposes to make water and oxygen gas.

Complete the balanced symbol equation for the reaction.

Describe a test and its result which shows that the gas produced in the reaction is oxygen.

Test........

Result........

A hydrogen peroxide solution produces oxygen gas slowly.

A student adds a piece of potato to the hydrogen peroxide solution. The potato contains a biological catalyst.

What name is given to biological catalysts?

Describe and explain the effect of adding the piece of potato to the hydrogen peroxide solution.

Include ideas about rate of reaction and activation energy.

The student measures the total volume of oxygen produced in the reaction with and without the piece of potato.

With the potato, the total volume is: increased, decreased, stays the same.

Tick (✓) one box.

The piece of potato added to the hydrogen peroxide solution is a six-sided cube.

Calculate the surface area of the piece of potato in cm². (i)

A student thinks that cutting the potato into smaller pieces will make the catalyst more effective.

Explain why the student is correct.

Tick (✓) one box.

The student measures the rate of reaction when the piece of potato is added to the hydrogen peroxide.

The rate of reaction is 1.5 cm³ / s.

They then measure the rate of reaction again with an increased concentration of hydrogen peroxide.

What would the rate of reaction be now?

Tick (✓) one box.

Hydrogen peroxide solution, H₂O₂(aq), decomposes to make water and oxygen gas.

Complete the balanced symbol equation for the reaction.

Describe a test and its result which shows that the gas produced in the reaction is oxygen.

Test........

Result........

A hydrogen peroxide solution produces oxygen gas slowly.

A student adds a piece of potato to the hydrogen peroxide solution. The potato contains a biological catalyst.

What name is given to biological catalysts?

Describe and explain the effect of adding the piece of potato to the hydrogen peroxide solution.

Include ideas about rate of reaction and activation energy.

The student measures the total volume of oxygen produced in the reaction with and without the piece of potato.

With the potato, the total volume is: increased, decreased, stays the same.

Tick (✓) one box.

The piece of potato added to the hydrogen peroxide solution is a six-sided cube.

Calculate the surface area of the piece of potato in cm². (i)

A student thinks that cutting the potato into smaller pieces will make the catalyst more effective.

Explain why the student is correct.

Tick (✓) one box.

The student measures the rate of reaction when the piece of potato is added to the hydrogen peroxide.

The rate of reaction is 1.5 cm³ / s.

They then measure the rate of reaction again with an increased concentration of hydrogen peroxide.

What would the rate of reaction be now?

Tick (✓) one box.

What are catalysts found in biological systems called?

A Bacteria

B Enzymes

C Isotopes

D Vitamins

Which of the catalysts is an example of an enzyme ?

A Alumina – used in the cracking of hydrocarbons

B Copper – used in the reaction between zinc and dilute sulfuric acid

C Lipase – used to help humans absorb fats

D Manganese oxide – used in the decomposition of hydrogen peroxide

The diagram shows the reaction profile for an uncatalysed reaction.

How does adding a catalyst to the reaction change the reaction profile?

A X is larger

B X is smaller

C Y is larger

D Y is smaller

Which reactions can be catalysed by an enzyme?

A Combustion reactions

B Electrolysis of metal ores

C Reactions in biological systems

D Reactions of metals with acids

Which reactions can be catalysed by an enzyme?

A Combustion reactions

B Electrolysis of metal ores

C Reactions in biological systems

D Reactions of metals with acids

A student has four different solids.

• One of the solids is a catalyst.

• The student tests 1 g of each solid in a chemical reaction.

The table shows the student’s observations for each solid.

Which solid is the catalyst?

The processing of crude oil by the petrochemical industry can be shown by different experiments.

Fig. 14.1 shows an experiment where paraffin is turned into decane and gas X.

Fig. 14.1

Fig. 14.2 shows the reaction of paraffin, C₁₄H₃₀, to make decane, C₁₀H₂₂, and gas X.

Fig. 14.2

Complete the sentences below to describe the experiment.

The experiment is called cracking / displacement / distillation.

It is an example of combustion / reduction / thermal decomposition.

The porous pot in Fig. 14.1 acts as a catalyst in the reaction.

What effect does the porous pot have on the rate of the reaction ?

decreases it
increases it
no effect

What effect does the porous pot have on the activation energy of the reaction?

decreases it
increases it
no effect

Use Fig. 14.2 to answer these questions.

Write the formula of gas X.

Describe what happens to a molecule of paraffin as it turns into a molecule of decane.

A student investigates the reaction between zinc and dilute sulfuric acid.

The student observes that bubbles are produced slowly during the reaction.

They want to find a catalyst for the reaction. They repeat the experiment, but each time they add a small piece of a different metal, R, S and T.

Look at the student’s results.

State if the metals, R, S and T are catalysts or not.

Explain your answers using the information in the table and your knowledge of catalysts.

A student investigates the reaction between zinc and dilute sulfuric acid.

The student observes that bubbles are produced slowly during the reaction.

They want to find a catalyst for the reaction. They repeat the experiment, but each time they add a small piece of a different metal, R, S and T.

Look at the student’s results.

State if the metals, R, S and T are catalysts or not.

Explain your answers using the information in the table and your knowledge of catalysts.

What is an example of a biological catalyst?

A A lipid

B An amino acid

C An enzyme

D A substrate

Hydrogen peroxide solution decomposes slowly to form water and oxygen.

Look at the equation for the reaction.

2H₂O₂(aq) → 2H₂O(l) + O₂(g)

This reaction, shown in Fig. 13.1, is very slow.

Fig. 13.1

A student thinks that adding manganese(IV) oxide, MnO₂, will catalyse the decomposition reaction.

Her experiment is shown in Fig. 13.2.

When she puts the glowing spill into the test tube in Fig. 13.2 the spill relights.

The student separates the manganese(IV) oxide from the reaction mixture.

She adds this manganese(IV) oxide to a new solution of hydrogen peroxide.

Predict the results of this experiment if manganese(IV) oxide is a catalyst.

Explain your answer.

How does a catalyst speed up a reaction?

A It decreases the activation energy.

B It decreases the energy of the reactant particles.

C It increases the activation energy.

D It increases the energy of the reactant particles.

Which statement about catalysts is correct?

A A catalyst decreases the rate of many different reactions.

B A catalyst for one reaction will be the catalyst for many different reactions.

C A catalyst has no effect on the rate of the reaction.

D A catalyst usually increases the rate of a reaction.

Why does a catalyst speed up a chemical reaction?

A It causes the reactants to collide less frequently.

B It decreases the overall energy change of the reaction.

C It lowers the activation energy of the reaction.

D It makes more product.