Question

10 ml of 0.5 M HCl is mixed with 30 ml of 0.3 M HCl, the molarity of the solution is:

• A. 0.40 M
• B. 0.25 M
• C. 0.35 M
• D. 0.68 M

Hint:

The molarity of a solution after mixing is calculated using the dilution formula.

Answer 1

The Correct Option is A

Step 1: Understanding molarity and dilution.
To calculate the molarity of the resulting solution, we use the equation for dilution: \[ M_1 V_1 + M_2 V_2 = M_3 (V_1 + V_2) \] Where \(M_1\) and \(M_2\) are the initial molarities, and \(V_1\) and \(V_2\) are the volumes of the two solutions.

Step 2: Substituting the given values.
\[ (0.5 \, \text{M} \times 10 \, \text{ml}) + (0.3 \, \text{M} \times 30 \, \text{ml}) = M_3 \times (10 \, \text{ml} + 30 \, \text{ml}) \] \[ (5) + (9) = M_3 \times 40 \] \[ M_3 = \frac{14}{40} = 0.40 \, \text{M} \]

Final Answer: \[ \boxed{\text{A) 0.40 M}} \]