CHEM - Rate of Reaction
Chemistry, rate of reaction, catalyst - IGCSE | IBDP | DSE | GCE | AP Chemistry
Rate of Reaction
Rate of reaction is the amount of reactant used up or amount of product formed per unit time.
Rate of reaction = (amount of reactant used up) ÷ (time taken)
Rate of reaction = (amount of product formed) ÷ (time taken)
For IGCSE Chemistry, it's important to understand how these factors 👇 affect rate of reaction
Factors that Affect Rate of Reaction
I. Surface Area of a Solid
II. Concentration of a Solution
Let's take a look at some IGCSE Chemistry questions on rate of reactions 😄
A student investigates the rate of decomposition of hydrogen peroxide solution. The diagram shows the apparatus he uses in his experiments. The equation for the decomposition is
2H2O2 → 2H2O + O2
(a) The student keeps the amount, in moles, of H2O2 in the solution constant at the start of each experiment. State two properties of the solution that he should keep the same to ensure that the amount of H2O2 is the same in each experiment.
(b) The student carries out the experiment five times. He uses a different solid in each experiment to see how effective each solid is as a catalyst in the decomposition. He removes the bung, adds a small amount of one of the solids and quickly replaces the bung. He records the time taken to collect 100 cm3 of oxygen in the syringe.
(i) Which solid does not seem to act as a catalyst?
(c) In the first experiment the student added 1g of solid A. Describe what he could do with the contents of the conical flask at the end of the experiment to show that A was a catalyst, and not a reactant.
The student investigated the effect that changing the concentration of the hydrogen peroxide solution has on the rate of the decomposition of hydrogen peroxide. He used solid manganese(IV) oxide as the catalyst in each experiment. This is the method he used.
(a) (i) State one property of each substance that the student should keep the same in each experiment.
(ii) What is the purpose of the cotton wool?
(b) The graph shows the results of one of the student’s experiments.
(i) Why does the balance reading decrease during the experiment?
(ii) What does the slope of the curve indicate about the reaction?
(d) The results of some of the student’s other experiments are shown on this graph.
(i) Which one of the experiments was the fastest?
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