Reaction monitoring methods (titration, gas volume, temperature): Practice Questions

Which of the following methods for following the progress of a chemical reaction is considered a discontinuous monitoring technique?

The reaction between bromine and methanoic acid can be followed using several different methods:

\(Br_2(aq) + HCOOH(aq) \rightarrow 2Br^-(aq) + 2H^+(aq) + CO_2(g)\)

Which of the following monitoring methods is/are suitable for this reaction?

I. Colorimetry to monitor the concentration of \(Br_2(aq)\).
II. Measuring the change in gas pressure in a closed system.
III. Measuring the volume of gas produced in an open system connected to a gas syringe.

The reaction between peroxodisulphate ions and iodide ions is shown below:

\(S_2O_8^{2-}(aq) + 2I^-(aq) \rightarrow 2SO_4^{2-}(aq) + I_2(aq)\)

Which of the following monitoring methods is LEAST suitable for determining the initial rate of this reaction in a school laboratory?

Which of the following methods is least suitable for following the progress of the reaction between dilute nitric acid and potassium hydroxide solution?

Titrimetric analysis is used to monitor the rate of the alkaline hydrolysis of an ester:

\(CH_3COOCH_2CH_3(l) + OH^-(aq) \rightarrow CH_3COO^-(aq) + CH_3CH_2OH(aq)\)

Why is it essential to add the reaction samples to a large volume of ice-cold water immediately before performing the titration?

Explain why temperature measurement is a suitable method for monitoring the progress of the displacement reaction between zinc powder and aqueous copper(II) sulphate.

For an exothermic reaction occurring in solution, such as a neutralization reaction, explain how monitoring temperature changes over time can be effectively used to determine the reaction rate. What assumption is made about the heat transfer during this monitoring process?

A student needs to determine the rate of decomposition of hydrogen peroxide, \(2H_2O_2(aq) \rightarrow 2H_2O(l) + O_2(g)\). Compare the suitability of using titrimetric analysis and gas volume measurement for monitoring this reaction, outlining a key principle or advantage for each method.

A student uses a gas syringe to monitor the reaction between magnesium ribbon and excess dilute hydrochloric acid:
\( \text{Mg(s)} + 2\text{HCl(aq)} \rightarrow \text{MgCl}_2\text{(aq)} + \text{H}_2\text{(g)} \)
(a) State the physical property being measured to follow the progress of the reaction.
(b) Explain why measuring the change in mass of the reaction system is not a suitable method for monitoring this specific reaction in a school laboratory.

A student monitors the displacement reaction between excess zinc powder and \( 50.0 \text{ cm}^3 \) of \( 0.40 \text{ mol dm}^{-3} \) copper(II) sulphate solution in a well-insulated polystyrene cup:
\( \text{Zn(s)} + \text{CuSO}_4\text{(aq)} \rightarrow \text{ZnSO}_4\text{(aq)} + \text{Cu(s)} \)
(a) Explain why the rate of this reaction can be monitored by measuring the temperature change of the mixture.
(b) Calculate the number of moles of copper(II) sulphate used.
(c) Calculate the theoretical maximum temperature rise (\( \Delta T \)) for this reaction. (Given: The enthalpy change of reaction is \( -210 \text{ kJ mol}^{-1} \); specific heat capacity of the solution is \( 4.2 \text{ J g}^{-1} \text{K}^{-1} \); density of the solution is \( 1.0 \text{ g cm}^{-3} \)).