Question

When potassium metal is placed in water a large amount of energy is released as potassium hydroxide and hydrogen gas are produced in the reaction 2k(s)+2h2o=2koh(aq)+h2(g). Your lab partner says this is a redox reaction and a combustion reaction. Do you agree? Defend your answer by explaining whether or not it meets the requirements of each type of reaction.

Answer 1

Explanation:

$2K(s)+2H_2O\rightarrow 2KOH(aq)+H_2(g)$

The given reaction is redox reaction but not combustion reaction.

Redox reaction : It is a chemical reaction in which oxidation and reduction occurs simultaneously.Oxidation is gaining of electrons and reduction is loosing of electrons.

$K\rightarrow K^++e^-$ oxidation

$2H^++2e^-\rightarrow H_2$ reduction

Potassium when reacts with water ,gives potassium ion in aqueous medium and combines with hydroxide ion present in water to form potassium hydroxide where as $H^+$ ions of water by gaining electrons (from potassium in water) gives hydrogen gas.

Hence , yes it is a redox reaction

Combustion reaction are the chemical reaction in which one reactant react with oxygen molecule to give heat and light.

Here in given reaction no oxygen molecule is appearing on reactant side.

Hence not a combustion reaction.