Exam code: 9701
Hydrogen gas reacts with bromine gas.
Which row explains why the rate of reaction is higher at 500 K than at 400 K?
collision frequency | proportion of effective collisions | activation energy | |
|---|---|---|---|
A | increases | increases | decreases |
B | increases | increases | remains constant |
C | increases | remains constant | decreases |
D | remains constant | increases | remains constant |
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What is the main reason for the increase in the rate of a reaction when the temperature increases?
the activation energy of the reaction decreases
the activation energy of the reaction increases
the frequency of collisions between molecules increases
more molecules have energy greater than or equal to the activation energy
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The rate of a reaction roughly doubles when the temperature is increased from 40 °C to 50 °C.
Which statement explains this?
the average kinetic energy of each molecule doubles
the average velocity of the molecules doubles
the frequency of molecular collisions doubles
the number of molecules with energy greater than or equal to the activation energy doubles
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The pressure of a fixed mass of gaseous reactants is increased at constant temperature.
What is the reason for the resulting increase in the rate of reaction?
the activation energy of the reaction decreases
the average kinetic energy of the molecules increases
the frequency of collisions between molecules increases
the proportion of molecules with energy greater than or equal to the activation energy increases
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Two experiments are carried out to measure the rate of reaction between solid calcium carbonate and dilute hydrochloric acid.
Experiment 1: 1.5 g of CaCO3 (s) is added to 100 cm3 of 0.50 mol dm-3 HCl (aq).
Experiment 2: 1.5 g of CaCO3 (s) is added to a mixture of 100 cm3 of 0.50 mol dm-3 HCl (aq) and 100 cm3 of distilled water.
The initial rate of reaction in Experiment 1 is higher than the initial rate in Experiment 2.
Which statement explains this?
adding water decreases the proportion of reacting particles with energy greater than or equal to the activation energy
adding water decreases the proportion of effective collisions between reacting particles
adding water increases the activation energy of the reaction
adding water reduces the frequency of collisions between reacting particles
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Two experiments are carried out to measure the rate of reaction between solid calcium carbonate and dilute hydrochloric acid.
Experiment 1: 1.5 g of CaCO3 (s) is added to 100 cm3 of 0.50 mol dm-3 HCl (aq).
Experiment 2: 1.5 g of CaCO3 (s) is added to a mixture of 100 cm3 of 0.50 mol dm-3 HCl (aq) and 100 cm3 of distilled water.
The initial rate of Experiment 1 is higher than the initial rate of Experiment 2.
Which row explains the difference in the initial rate when water is added?
frequency of collisions between reacting particles | proportion of effective collisions | activation energy | |
|---|---|---|---|
A | decreases | decreases | remains constant |
B | decreases | remains constant | remains constant |
C | decreases | remains constant | increases |
D | remains constant | decreases | increases |
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The equation for a reaction is shown.
NaOH (aq) + HCl (aq) → NaCl (aq) + H2O (l)
The rate of this reaction can be determined by monitoring the concentration of which species over time?
H+
Cl-
Na+
H2O
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When 1 cm3 of 0.1 mol dm-3 HCl (aq) is added to 10 cm3 of 0.02 mol dm-3 Na2S2O3 (aq), a pale yellow precipitate forms slowly.
When the experiment is repeated using 10 cm3 of 0.05 mol dm-3 Na2S2O3 (aq), the precipitate forms more quickly.
Which statement explains this observation?
the reacting particles collide more frequently
the collisions between reacting particles are more energetic
the activation energy of the reaction is lower
the proportion of particles with energy greater than or equal to the activation energy increases
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A quantity of solid Y was placed in a previously evacuated vessel, and the apparatus was then held at a series of different temperatures. At each temperature, the mass of Y in the vapour state was calculated from pressure measurements. The results are shown below.
What can be deduced from the diagram?
liquid appears at temperature T
the initial mass of solid Y placed in the vessel is m
the pressure of the vapour remains constant at temperatures above T
the volume of the vapour increases at temperatures above T
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Curve 1 shows the volume of oxygen produced over time during the decomposition of 100 cm3 of 1.0 mol dm-3 hydrogen peroxide in the presence of a manganese(IV) oxide catalyst.
Which change to the experiment produces curve 2?
raising the temperature
adding more manganese(IV) oxide catalyst
adding water
adding some 0.1 mol dm-3 hydrogen peroxide
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