Question

which of the following is a combination reaction? a) d) agno3 (aq) + nacl (aq) → agcl (s) + nano3 (aq) b) a) cacl2 (aq) + na2so4 (aq) → caso4 (s) + 2nacl (aq) c) c) n2 (g) + o2 (g) → 2no (g) d) b) koh (aq) + hno3 (aq) → hn2o (l) + kno3 (aq)

Explanation:

A combination reaction is one where two or more substances combine to form a single product. In option C, nitrogen gas ($N_2$) and oxygen gas ($O_2$) combine to form nitrogen - monoxide ($NO$). Options A and B are double - displacement reactions where the cations and anions of two different compounds exchange places. Option D is an incorrect reaction as the products are not formed as shown; a correct acid - base neutralization reaction of $KOH$ and $HNO_3$ would form $H_2O$ and $KNO_3$.

Answer:

C. $N_2(g)+O_2(g)
ightarrow 2NO(g)$