This is an acid-base reaction (neutralization): HI is an acid, KOH is a base.

### Word equation

hydrogen iodide + potassium hydroxide → potassium iodide + water

### Input interpretation

HI + KOH → KI + H2O

Hydrogen iodide potassium hydroxide potassium iodide water

### Balanced equation

Balance the chemical equation algebraically:

HI + KOH → KI + H2O

Add stoichiometric coefficients, c,, to the reactants and products:

c1 HI + c2 KOH → c3 KI + c4 H2O

Set the number of atoms in the reactants equal to the number of atoms in the products for H, I, K and O:

H: c1 + c2 = 2c4

I: c1 = c3

K: c2 = c3

O: c2 = c4

Since the coefficients are relative quantities and underdetermined, choose a coefficient to set arbitrarily. To keep the coefficients small, the arbitrary value is ordinarily one. For instance, set c1 = 1 and solve the system of equations for the remaining coefficients:

c1 = 1 c2=1

c3 = 1 c4=1

Substitute the coefficients into the chemical reaction to obtain the balanced equation: