IGCSE Coordinated Chemistry Workout 28

Which statement describes an exothermic reaction?

• Heat energy is transferred from the surroundings and the temperature decreases.

• Heat energy is transferred from the surroundings and the temperature increases.

• Heat energy is transferred to the surroundings and the temperature decreases.

• Heat energy is transferred to the surroundings and the temperature increases.

Dilute hydrochloric acid is added to lumps of calcium carbonate. Which change decreases the rate of the reaction?

• Decrease the temperature of the acid.

• Increase the concentration of the acid.

• Use a larger volume of the acid.

• Use powdered calcium carbonate.

When iron is heated with steam, a black solid is formed. Which statement about this reaction is correct?

• Iron has been oxidised because it has gained oxygen.

• Iron has been reduced because it removed oxygen from water.

• Iron oxide has been reduced because it contains oxygen.

• Water has been oxidised because it contains oxygen.

Zinc sulfate is made by adding zinc oxide to dilute sulfuric acid. The steps used to obtain zinc sulfate crystals are listed.

1 filter the solution to remove excess zinc oxide

2 warm the zinc sulfate solution

3 add excess zinc oxide and stir

4 filter and dry the crystals

What is the correct order of the steps?

• 1 → 3 → 4 → 2

• 2 → 1 → 3 → 4

• 3 → 1 → 2 → 4

• 3 → 2 → 1 → 4

Which diagram represents the structure of an alloy?

• A

• B

• C

• D

Four iron nails are placed in four test-tubes as shown. In which test-tube does the iron nail rust most quickly?

• A

• B

• C

• D

During the manufacture of sulfuric acid by the Contact process, sulfur trioxide is produced. The sulfur trioxide is dissolved in concentrated sulfuric acid. Which statement explains why sulfur trioxide is not dissolved in water?

• The reaction is too endothermic.

• The reaction is too exothermic.

• The reaction is too slow.

• The reaction needs a high pressure.

Ethanol is manufactured by reacting ethene with steam in the presence of a catalyst. Which type of reaction occurs?

• addition

• oxidation

• polymerisation

• reduction

What is a harmful effect of an increase in carbon dioxide in the atmosphere?

• It allows more heat from the Sun to enter the Earth’s atmosphere.

• It decreases the rate at which organisms respire.

• It increases the rate at which plants photosynthesise.

• It prevents reflected heat from leaving the Earth’s atmosphere.

Which statement about noble gases is correct?

• All noble gases have eight electrons in their outer shell.

• Argon is used to fill weather balloons.

• Neon atoms have the same electronic structure as sodium ions.

• The element with atomic number 4 is a noble gas.