1 M, 2.5 litre NaOH solution is mixed with another 0.5 M and 3 litre NaOH solution. The molarity of the result

Question

1 M, 2.5 litre NaOH solution is mixed with another 0.5 M and 3 litre NaOH solution. The molarity of the resultant solution will be:

Accepted Answer

1. **Identify the Principle:** Molarity ($M$) is defined as the number of moles of solute dissolved in one litre of solution . When mixing two solutions of the same solute, the total number of moles is the sum of the moles in each solution, and the total volume is the sum of the individual volumes.
2. **Calculate Moles in Solution 1 ($n_1$):**
   $$ n_1 = M_1 	imes V_1 = 1	ext{ M} 	imes 2.5	ext{ L} = 2.5	ext{ mol} $$
3. **Calculate Moles in Solution 2 ($n_2$):**
   $$ n_2 = M_2 	imes V_2 = 0.5	ext{ M} 	imes 3	ext{ L} = 1.5	ext{ mol} $$
4. **Calculate Resultant Molarity ($M_{mix}$):**
   $$ n_{total} = n_1 + n_2 = 2.5 + 1.5 = 4.0	ext{ mol} $$
   $$ V_{total} = V_1 + V_2 = 2.5 + 3.0 = 5.5	ext{ L} $$
   $$ M_{mix} = \frac{n_{total}}{V_{total}} = \frac{4.0}{5.5} \approx 0.727	ext{ M} $$
5. **Rounding:** The value rounds to approximately $0.73	ext{ M}$.

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