Quick questions on Rates of reaction - WJEC A-Level Chemistry

The distribution plots the number of molecules against energy. The area beyond $E_a$ represents molecules able to react. Raising the temperature shifts the curve to higher energies and flattens the peak, so a much larger fraction exceeds $E_a$, which is why a small temperature rise produces a large rate increase. A catalyst lowers $E_a$, moving the threshold leftward so more molecules can react at the same temperature.

Rate is found by measuring how a property linked to concentration changes with time. Common methods include collecting and measuring the volume of gas produced, recording the mass loss as a gas escapes, or timing how long a precipitate takes to obscure a mark (the classic sodium thiosulfate and acid experiment). Plotting concentration against time gives a curve whose gradient is the rate, steepest at the start when concentrations are highest and levelling off as reactants are used up.

Platinum and rhodium catalysts in car exhausts lower the activation energy for converting toxic $\text{CO}$ and $\text{NO}_x$ into $\text{CO}_2$ and $\text{N}_2$, a vital rate application. Enzymes in the body. Biological catalysts lower activation energies so metabolic reactions proceed fast at body temperature, the same Maxwell-Boltzmann logic applied to living systems.

State the two conditions a collision must meet to be successful. [1 mark]

Explain how a catalyst increases the rate of reaction. [2 marks]

State the effect of increasing the surface area of a solid reactant on rate. [1 mark]

State the effect of a catalyst on the activation energy and on the enthalpy change of a reaction. [1 mark]

Name one method of following the rate of a reaction that produces a gas. [1 mark]