Chemistry 0620 · IGCSE · Rate of reaction

Rate of reaction — practice question

At room temperature and pressure, r.t.p., aqueous hydrogen peroxide, $\text{H}_2\text{O}_2$, decomposes slowly into water and oxygen. Manganese(IV) oxide catalyses this reaction. $2\text{H}_2\text{O}_2$(aq) $\rightarrow$ $2\text{H}_2\text{O}$(l) + $\text{O}_2$(g)
(a)[1]

State the test for oxygen gas and the observation.

(b(i))[1]

State how the graph in Fig. 4.1 shows the rate of reaction at time $t_2$ is lower than at time $t_1$.

(b(ii))[2]

Explain, using collision theory, why the rate of reaction at time $t_2$ is lower than at time $t_1$.

(b(iii))[2]

On Fig. 4.1, sketch the graph obtained when the experiment is repeated using aqueous hydrogen peroxide at a higher temperature. All other conditions remain unchanged.

(c)[5]

Calculate the concentration of the aqueous hydrogen peroxide in g/dm$^3$ by following these steps: • Work out the amount of oxygen gas produced in moles. • Find the amount of hydrogen peroxide that reacts in moles. • Work out the concentration of aqueous hydrogen peroxide in mol/dm$^3$. • Work out the concentration of aqueous hydrogen peroxide in g/dm$^3$.

(d)[1]

Suggest the identity of one other metal oxide that also catalyses this reaction.

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