Paper 2 · November 2019 · Stoichiometry and Mole Calculations
In a titration where sodium hydroxide solution, NaOH(aq), is added from a burette into a conical flask containing dilute sulfuric acid, H2SO4(aq), with 2-3 drops of a solution Y added to the acid beforehand, what is the role of solution Y?
AIt is the limiting reagent that determines the maximum yield of salt formed.
BIt is an indicator that changes colour to show the end point of the reaction.
CIt is a catalyst that increases the rate of the neutralisation reaction.
DIt is a buffer that keeps the pH of the mixture constant throughout the titration.
Explanation
Solution Y is an indicator: it changes colour according to pH, showing when the acid has been exactly neutralised (the end point).
Derived from ZIMSEC Chemistry 4024/2 Paper 2 Theory, November 2019, Q1