State the equation for the reaction between sodium and water.

State and explain one difference between the reactions of sodium and potassium with water.

\({\text{2Na(s)}} + {\text{2}}{{\text{H}}_{\text{2}}}{\text{O(l)}} \to {\text{2NaOH(aq)}} + {{\text{H}}_{\text{2}}}{\text{(g)}}\);

Accept multiple and fractional coefficients.

reaction with K is more vigorous than with Na / reaction with K causes \({{\text{H}}_2}{\text{(g)}}\) to ignite / a lilac flame is observed with K / more heat produced / more exothermic / OWTTE;

K is oxidized more readily than Na / K is more reactive than Na / K loses an electron more readily than Na / K is higher than Na in reactivity series / OWTTE;

Mark M1 and M2 independently.

Part (a) produced a wide variety of equations, some giving \({\text{N}}{{\text{a}}_{\text{2}}}{\text{O}}\) and/or H atoms as products.

Part (b) was generally answered correctly. In fact many answers went well beyond that required by the markscheme and would not have disgraced HL candidates.