Which of the following aqueous methods cannot be used to distinguish between a strong acid and a a weak acid?
Answer Details
The aqueous method that cannot be used to distinguish between a strong acid and a weak acid is the action on starch iodide paper.
The reason for this is that both strong acids and weak acids are capable of reacting with the starch-iodide paper to produce a blue-black color. This reaction occurs because the iodide ions in the paper react with the hydrogen ions released by the acids to form hydrogen iodide gas. The hydrogen iodide gas then reacts with the starch in the paper to produce the blue-black color.
Conductivity measurement and measurement of pH are useful methods to distinguish between strong acids and weak acids. Strong acids completely dissociate in water, producing a high concentration of ions that conduct electricity well and have a very low pH. Weak acids only partially dissociate in water, producing a lower concentration of ions that conduct electricity less efficiently and have a higher pH.
Measurement of heat of neutralization is also a useful method to distinguish between strong acids and weak acids. Strong acids release more heat during neutralization than weak acids because they produce more hydrogen ions when they react with a base.