Problem

The key is comparing each metal's reactivity to hydrogen using the reactivity series (or standard reduction potentials). A metal reacts with dilute HCl only if it's more reactive than hydrogen—meaning it can displace $\text{H}^+$ ions and form $\text{H}_2$ gas. Silver sits below hydrogen in the series and won't react, while iron and zinc both sit above it and will. This is a quick check of whether electron transfer can spontaneously occur.

The key is comparing each metal's reactivity to hydrogen using the reactivity series (or standard reduction potentials). A metal reacts with dilute HCl only if it's more reactive than hydrogen—meaning it can displace $\text{H}^+$ ions and form $\text{H}_2$ gas. Silver sits below hydrogen in the series and won't react, while iron and zinc both sit above it and will. This is a quick check of whether electron transfer can spontaneously occur.