Unstable potassium oxide reacts with water vapor in the air to produce potassium hydroxide:

K2O + H2O → KOH

What, if anything, should be done to balance this chemical equation?

A) Nothing. It is balanced.

B) Put a "2" in front of the KOH.

C) Put a "4" in front of the KOH.

D) Put ".5" in front of both K2O and H2O.

B) Put a "2" in front of the KOH.

Explanation:

We are given;

The unbalanced equation;

K₂O + H₂O → KOH

Why is it unbalanced?

The equation is unbalanced because the number of atoms of each elements are not equal on both sides of the equation. That is; Reactant side; 2 K atoms, 2 H atoms, and 2 O atoms while the product side has 1 K atom, 1 O atom and 1 H atom.

How should we make the equation balanced?

In order to balance an equation we put appropriate coefficients in front of reactants or products. In this case, we can balance the equation by putting 1 in front of K₂O, 1 in front H₂O and 2 in front of KOH which simply means putting a "2" in front of KOH Therefore, the balanced equation is;

K₂O + H₂O → 2KOH