The molarity of a solution obtained by mixing 800 mL of 0.5 M HCl with 200 mL of 1 M HCl will be

Options

A. 0.8 M
B. 0.6 M
C. 0.4 M
D. 0.2 M

Answer

To find the molarity of a solution obtained by mixing 800 mL of 0.5 M HCl with 200 mL of 1 M HCl, we can follow these steps:

### Step 1: Convert volumes from mL to L
- Volume of first solution (V1) = 800 mL = 800/1000 = 0.8 L
- Volume of second solution (V2) = 200 mL = 200/1000 = 0.2 L

### Step 2: Calculate the number of moles of HCl in each solution
- For the first solution (0.5 M HCl):
\[ N1 = M1 \times V1 = 0.5 \, \text{mol/L} \times 0.8 \, \text{L} = 0.4 \, \text{mol} \]

- For the second solution (1 M HCl):
\[ N2 = M2 \times V2 = 1 \, \text{mol/L} \times 0.2 \, \text{L} = 0.2 \, \text{mol} \]

### Step 3: Calculate the total number of moles of HCl
- Total moles (N_total):
\[ N_{\text{total}} = N1 + N2 = 0.4 \, \text{mol} + 0.2 \, \text{mol} = 0.6 \, \text{mol} \]

### Step 4: Calculate the total volume of the mixed solution
- Total volume (V_total):
\[ V_{\text{total}} = V1 + V2 = 0.8 \, \text{L} + 0.2 \, \text{L} = 1.0 \, \text{L} \]

### Step 5: Calculate the molarity of the mixed solution
- Molarity (M):
\[ M = \frac{N_{\text{total}}}{V_{\text{total}}} = \frac{0.6 \, \text{mol}}{1.0 \, \text{L}} = 0.6 \, \text{M} \]

### Final Answer:
The molarity of the solution obtained by mixing 800 mL of 0.5 M HCl with 200 mL of 1 M HCl is **0.6 M**.

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