Question

A volume of 25cm3 of a carbonate solution of concentration 0.2mol dm-3 was neutralized by 20 cm3 of acid of concentration 0.5 mol dm-3. The mole ratio in which the reactants combine is?

1 mol of carbonate to 1 mol of acid

1 mol of carbonate to 2 mol of acid

2 mol carbonate to 1 mol of acid

3 mol of carbonate to 1 mol of acid

Answer 1

Answer: 1 mol of carbonate to 2 mol of acid

Explanation:

To calculate the number of moles for given molarity, we use the equation:

$\text{Molarity of the solution}=\frac{\text{Moles of solute}\times 1000}{\text{Volume of solution in ml}}$  

a) $\text{Moles of carbonate}=\frac{0.2moldm^{-3}\times 25cm^3}{1000}=0.005mol$

b) $\text{Moles of acid}=\frac{0.5moldm^{-3}\times 20cm^3}{1000}=0.01mol$

Thus the mole ratio of carbonate to acid is = $\frac{0.005}{0.01}=\frac{1}{2}$