Question: 1 gm NaOH and 1 gm HCl are mixed together in one litre solution. Find the nature of solution -...

Question

1 gm NaOH and 1 gm HCl are mixed together in one litre solution. Find the nature of solution -

Answer 1

Solution

The reaction between NaOH (a strong base) and HCl (a strong acid) is a neutralization reaction:

$NaOH(aq) + HCl(aq) \rightarrow NaCl(aq) + H_2O(l)$

To determine the nature of the solution, we need to find the number of moles of each reactant.

Given mass of NaOH = 1 gm
Molar mass of NaOH = 23 (Na) + 16 (O) + 1 (H) = 40 g/mol
Number of moles of NaOH = $\frac{\text{mass}}{\text{molar mass}} = \frac{1 \text{ gm}}{40 \text{ g/mol}} = 0.025$ mol

Given mass of HCl = 1 gm
Molar mass of HCl = 1 (H) + 35.5 (Cl) = 36.5 g/mol
Number of moles of HCl = $\frac{\text{mass}}{\text{molar mass}} = \frac{1 \text{ gm}}{36.5 \text{ g/mol}} \approx 0.0274$ mol

According to the balanced chemical equation, 1 mole of NaOH reacts with 1 mole of HCl.
We have 0.025 mol of NaOH and approximately 0.0274 mol of HCl.
Since the number of moles of HCl (0.0274 mol) is greater than the number of moles of NaOH (0.025 mol), HCl is the excess reactant and NaOH is the limiting reactant.

The reaction consumes 0.025 mol of NaOH and 0.025 mol of HCl.
Moles of HCl remaining = Initial moles of HCl - Moles of HCl reacted
Moles of HCl remaining $\approx 0.0274 \text{ mol} - 0.025 \text{ mol} = 0.0024$ mol

Since there is excess HCl remaining in the solution, the solution will be acidic. HCl is a strong acid, and the presence of excess HCl determines the acidic nature of the solution.

The volume of the solution is 1 litre. The concentration of the remaining HCl is approximately $\frac{0.0024 \text{ mol}}{1 \text{ L}} = 0.0024$ M.
Since HCl is a strong acid, it dissociates completely, so $[H^+] \approx 0.0024$ M.
Since $[H^+] > 10^{-7}$ M, the solution is acidic.