500 ml of 2M NaCl solution was mixed with 200 ml of 2 M NaCl solution. Calculate the molarity of NaCl in final solution

Answer

To calculate the molarity of NaCl in the final solution after mixing two solutions, we can follow these steps:

### Step 1: Identify the given values
- Molarity of the first solution (M1) = 2 M
- Volume of the first solution (V1) = 500 ml = 0.5 L
- Molarity of the second solution (M2) = 2 M
- Volume of the second solution (V2) = 200 ml = 0.2 L

### Step 2: Calculate the number of moles of NaCl in each solution
The number of moles (n) can be calculated using the formula:
\[ n = M \times V \]

For the first solution:
\[ n_1 = M_1 \times V_1 = 2 \, \text{M} \times 0.5 \, \text{L} = 1 \, \text{mol} \]

For the second solution:
\[ n_2 = M_2 \times V_2 = 2 \, \text{M} \times 0.2 \, \text{L} = 0.4 \, \text{mol} \]

### Step 3: Calculate the total number of moles of NaCl
\[ n_{\text{total}} = n_1 + n_2 = 1 \, \text{mol} + 0.4 \, \text{mol} = 1.4 \, \text{mol} \]

### Step 4: Calculate the total volume of the final solution
\[ V_{\text{total}} = V_1 + V_2 = 0.5 \, \text{L} + 0.2 \, \text{L} = 0.7 \, \text{L} \]

### Step 5: Calculate the final molarity of NaCl
Using the formula for molarity:
\[ M_f = \frac{n_{\text{total}}}{V_{\text{total}}} \]

Substituting the values:
\[ M_f = \frac{1.4 \, \text{mol}}{0.7 \, \text{L}} = 2 \, \text{M} \]

### Conclusion
The molarity of NaCl in the final solution is **2 M**.

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