Which one of the following is not a combination reaction?
A. HNO3 (aq) + KOH (aq) → H2O (l) + KNO3 (aq)
B. 2CaO + 3CO2 → 2CaCO3
C. Na2O + CO2 → Na2CO3
D. 4Fe + 3O2 → 2Fe2O3

Respuesta :

Since we see that the only one that results in two compounds is a, that is teh correct answer. 

Answer:  A. HNO3 (aq) + KOH (aq) → H2O (l) + KNO3 (aq)

Answer:

A. HNO3 (aq) + KOH (aq) → H2O (l) + KNO3 (aq)

Explanation:

A combination reaction is a chemical reaction in which two or more substances combine to form a single substance under suitable conditions. As a result of a chemical reaction new substances are formed. Thus, these reactions are also called synthesis. Combination reactions are of three types. Reaction between metals and non-metals, reaction between two non-metals and Reaction between elements and compounds. Thus, among the given options A does not fall in the group of combination reaction.