Zinc powder is reacted with dilute hydrochloric acid. $\text{Zn} + 2\text{HCl} \rightarrow \text{ZnCl}_2 + \text{H}_2$ If $20.0\,\text{cm}^3$ of dilute hydrochloric acid is added to excess zinc, the volume of hydrogen gas obtained at room temperature and pressure is $60.0\,\text{cm}^3$. Calculate the concentration, in $\text{mol dm}^{-3}$, of the dilute hydrochloric acid.
The reaction is carried out again, but large pieces of zinc are used in place of zinc powder. All other conditions remain unchanged. Describe how the rate of reaction changes. Explain your answer using ideas about collisions between particles.
Dilute hydrochloric acid is electrolysed. Write an ionic equation for the reaction at the cathode.
Zinc is used to stop iron from rusting. State the essential conditions needed for rusting.
Explain how zinc prevents iron from rusting by sacrificial protection.
Give one example of where sacrificial protection is used.