CIE iGCSE Co-Ordinated Science C6.2 Rate of reaction Exam Style Questions Paper 1
Question
Dilute hydrochloric acid is added to excess solid calcium carbonate. Which change increases the rate of this reaction?
A. decrease the concentration of the acid
B. decrease the volume of the acid
C. reduce the size of the solid particles
D. reduce the temperature
▶️Answer/Explanation
Answer: C. reduce the size of the solid particles
Explanation: Reducing the size of solid particles increases the surface area available for the reaction, which increases the rate of reaction. Decreasing the concentration, volume, or temperature would slow down the reaction.
Question
A known mass of solid sodium carbonate is added to excess hydrochloric acid. Which conditions give the shortest reaction time?
| solid particle size | acid concentration | |
|---|---|---|
| A | large | high |
| B | large | low |
| C | small | high |
| D | small | low |
▶️Answer/Explanation
Answer: C) small | high
Explanation: Smaller particle size increases the surface area, and higher acid concentration increases the reaction rate, leading to the shortest reaction time.
Question
Aqueous hydrogen peroxide decomposes slowly and produces water and oxygen gas.
The equation for this decomposition is shown.
2H2O2 → 2H2O + O2
The experiment is repeated using a catalyst.
Which row describes the results for the second experiment?
A less time to produce first 20 cm3 of gas / same total volume of gas
B less time to produce first 20 cm3 of gas / more total volume of gas
C more time to produce first 20 cm3 of gas / same total volume of gas
D more time to produce first 20 cm3 of gas / more total volume of gas
▶Answer/Explanation
Answer: A
Explanation: A catalyst speeds up the reaction, so less time is needed to produce the first 20 cm3 of gas. However, the total volume of gas produced remains the same.
Question
When solid pieces of calcium carbonate are added to dilute hydrochloric acid in a flask, carbon dioxide gas is given off.
The mass of the flask and its contents are measured over time.
Two different experiments are carried out. In both experiments the acid is in excess.
The results of these two experiments are shown.
Which statement explains the different shapes of the curves?
A Experiment 2 uses a catalyst.
B Experiment 2 uses acid at a higher temperature.
C Experiment 2 uses acid that is more dilute.
D Experiment 2 uses powdered calcium carbonate.
▶️Answer/Explanation
Ans :A
Question
A fixed mass of a solid is reacted with a liquid.
The volume of gas given off from the reaction over time is shown by line S.
Which change to the reaction conditions produces line T on the graph?
A increasing the amount of catalyst added
B increasing the concentration of the liquid
C increasing the particle size of the solid
D increasing the temperature of the reaction
▶️Answer/Explanation
Ans :C
Question
A chemical reaction produces a gas.
The volume of gas given off over time is measured.
The results are shown.
During which time period is the rate of reaction greatest?
(A) 0–10 seconds
(B) 20–30 seconds
(C) 40–50 seconds
(D) 60–70 seconds
▶️Answer/Explanation
Ans: A
Question
Two separate experiments X and Y are used to investigate the rate of the reaction between equal
masses of calcium carbonate and excess dilute hydrochloric acid.
The volume of carbon dioxide given off is measured over time.
A graph of the results is shown.
Which statement explains the difference between experiments X and Y?
(A) A catalyst is added to Y.
(B) A higher temperature is used in Y.
(C) Larger pieces of calcium carbonate are used in X.
(D) The acid is more concentrated in X.
▶️Answer/Explanation
Ans: D
Question
The rate of a reaction between a powdered metal and a dilute acid is investigated by measuring the volume of hydrogen gas produced per minute.
The investigation is repeated using a catalyst. The same mass of powdered metal and the same volume and concentration of acid is used.
Which statement about the second investigation is correct?
(A) The rate of the reaction is higher and a greater total volume of hydrogen is produced.
(B) The rate of the reaction is higher and the same total volume of hydrogen is produced.
(C) The rate of the reaction is lower and a smaller total volume of hydrogen is produced.
(D) The rate of the reaction is lower and the same total volume of hydrogen is produced.
▶️Answer/Explanation
Ans : B
Question
Which statement about rates of reaction is correct?
A Catalysts never affect the rate of reaction.
B Decreasing the temperature of a reaction increases the rate of reaction.
C Increasing the concentration of a reacting solution decreases the rate of reaction.
D Using smaller sized pieces of a solid increases the rate of reaction.
▶️Answer/Explanation
Ans : D
Question
Dilute hydrochloric acid reacts with calcium carbonate.
The equation for the reaction is shown.
CaCO3 + 2HCl → CaCl2 + CO2 + H2O
Which change increases the rate of the reaction?
(A) decreasing the temperature of the hydrochloric acid
(B) increasing the concentration of the hydrochloric acid
(C) increasing the size of the calcium carbonate particles
(D) increasing the volume of the hydrochloric acid
▶️Answer/Explanation
Ans: B
Question
Hydrogen gas is given off when zinc reacts with dilute sulfuric acid.
Which piece of apparatus is used to collect the hydrogen gas and measure its volume?
(A) balance
(B) gas syringe
(C) pipette
(D) test-tube
▶️Answer/Explanation
Ans: B
Question
Magnesium ribbon is reacted with 50 cm³ of dilute hydrochloric acid. Which change does not increase the rate of the reaction?
A. Increase the concentration of the hydrochloric acid.
B. Increase the temperature of the hydrochloric acid.
C. Increase the volume of the hydrochloric acid.
D. Use powdered magnesium.
▶️Answer/Explanation
Answer: C. Increase the volume of the hydrochloric acid.
Explanation: Increasing the volume of the hydrochloric acid without changing its concentration does not increase the rate of reaction. The rate depends on the concentration of reactants, temperature, and surface area (e.g., using powdered magnesium increases the surface area).
Question
Magnesium is tested as shown.
Magnesium + dilute hydrochloric acid → Test 1: Bubbles observed, Test 2: Lamp lights.
Which row shows the results of the tests?
| Test 1 | Test 2 | |
|---|---|---|
| A | Bubbles | Lamp does not light |
| B | Bubbles | Lamp lights |
| C | No bubbles | Lamp does not light |
| D | No bubbles | Lamp lights |
▶️Answer/Explanation
Answer: B. Bubbles, Lamp lights.
Explanation: Magnesium reacts with hydrochloric acid to produce hydrogen gas (bubbles) and the reaction is exothermic, which can light a lamp if connected to a circuit.
Question
When limestone is heated it thermally decomposes into lime. What is the word equation for this reaction?
A. calcium carbonate → calcium + carbon dioxide
B. calcium carbonate → calcium oxide + carbon dioxide
C. calcium hydrogencarbonate → calcium + carbon dioxide + water
D. calcium hydrogencarbonate → calcium oxide + carbon dioxide + water
▶️Answer/Explanation
Answer: B
Explanation: When limestone (calcium carbonate) is heated, it decomposes into calcium oxide (lime) and carbon dioxide. The correct word equation is: calcium carbonate → calcium oxide + carbon dioxide.
Question
Which processes are chemical changes?
1 conversion of steam to liquid water
2 cracking of alkanes
3 fractional distillation of petroleum
4 thermal decomposition of calcium carbonate
A 1 and 3
B 1 and 4
C 2 and 3
D 2 and 4
▶️Answer/Explanation
Answer: D
Explanation: Cracking of alkanes and thermal decomposition of calcium carbonate are chemical changes, as they involve the breaking and forming of chemical bonds.
Question
When 50 cm3 of dilute hydrochloric acid and excess solid sodium carbonate are mixed, they react to form carbon dioxide gas. The gas is collected in a gas syringe. The experiment is repeated using 25 cm3 of dilute hydrochloric acid.
Which statement about the second experiment compared to the first experiment is correct?
A It has the same initial rate of reaction and produces a lower volume of gas.
B It has the same initial rate of reaction and produces the same volume of gas.
C It has a slower initial rate of reaction and produces a lower volume of gas.
D It has a slower initial rate of reaction and produces the same volume of gas.
▶️Answer/Explanation
Answer: A
Explanation: The initial rate of reaction depends on the concentration of the acid, which is the same in both experiments. However, using half the volume of acid will produce half the volume of gas.
Question
Hydrogen peroxide decomposes very slowly. When element X is added, hydrogen peroxide decomposes much faster. Element X is unchanged at the end of this reaction.
What is element X?
▶️Answer/Explanation
Answer: D
Explanation: Element X is a catalyst, as it speeds up the decomposition of hydrogen peroxide without being consumed in the reaction. Catalysts remain unchanged at the end of a reaction.
Question
Which processes produce carbon dioxide?
1 acid reacting with a metal
2 respiration
3 combustion of ethanol
4 acid reacting with a metal oxide
A 1 and 2
B 1 and 4
C 2 and 3
D 3 and 4
▶️Answer/Explanation
Answer: C
Explanation: Respiration and the combustion of ethanol both produce carbon dioxide as a byproduct.
Question
Iron increases the rate of a reaction. What is the role of iron in this reaction?
A. catalyst
B. electrolyte
C. element
D. isotope
▶️Answer/Explanation
Answer: A
Explanation: Iron acts as a catalyst in this reaction. A catalyst increases the rate of a chemical reaction without being consumed in the process.