Question

Which equation describes a single-replacement reaction?

Responses

Cl2(g) + 2Kl(s) → 2KCl(s) + l2(g)

uppercase C lowercase l subscript 2 end subscript open parenthesis lowercase g close parenthesis plus 2 uppercase K l open parenthesis lowercase s close parenthesis rightwards arrow 2 uppercase K C lowercase l open parenthesis lowercase s close parenthesis plus uppercase l subscript 2 end subscript open parenthesis lowercase g close parenthesis

H2 (g) + Br2 (g)→2HBr (g)

uppercase H subscript 2 end subscript open parenthesis lowercase g close parenthesis plus uppercase B lowercase r subscript 2 end subscript open parenthesis lowercase g close parenthesis rightwards arrow 2 uppercase H B lowercase r open parenthesis lowercase g close parenthesis

2N2O5 (g)→O2 (g) +  4NO2 (g)

2 uppercase N subscript 2 end subscript uppercase O subscript 5 end subscript open parenthesis lowercase g close parenthesis rightwards arrow uppercase O subscript 2 end subscript open parenthesis lowercase g close parenthesis plus 4 uppercase N O subscript 2 end subscript open parenthesis lowercase g close parenthesis

2Na(s) +Cl2(g) → 2NaCl(s)

Answer 1

Cl2(g) + 2KI(s) → 2KCl(s) + I2(g)

Reason: This is a single‑replacement (displacement) reaction — chlorine (an element) replaces iodine in KI, producing KCl and elemental I2.