25cm\(^3\) of a 0.2 mol dm\(^3\) solution of Na\(_2\)CO\(_3\) requires 20 cm\(^3\) of a solution of HCl for neutralization. The concentration of the HCl solution is
-
0.5 mol dm3
- 0.6 mol dm3
- 0.2 mol dm3
- 0.4 mol dm3
The correct answer is: A
Explanation
First, write a balanced chemical equation or the reaction:
Na\(_2\)CO\(_3\) + 2HCl → 2NaCl + H\(_2\)O + CO\(_2\)
From the balanced equation, we can deduce that N\(_A\) = 2 , N\(_B\) = 1
We were also given from the question, C\(_A\) = ? C\(_B\) = 0.2 mol/dm\(^3\) V\(_A\) = 20cm\(^3\) V\(_B\) = 25 cm\(^3\)
Using the relationship, \(\frac{C_A V_A}{C_B V_B}\) = \(\frac{N_A}{N_B}\)
C\(_A\) = \(\frac{C_B V_B N_A}{V_A N_B}\)
C\(_A\) = \(\frac{0.2 X 25 X 2}{20 X 1}\) = 0.5 mol/dm\(^3\)