The molecular mass of metal chloride, `MCl`, is 74.5. The equivalent : mass of the metal M wil be -

Options

A. 39
B. 74.5
C. `110.0`
D. 35.5

Explanation

To find the equivalent mass of the metal M in the metal chloride \( MCl \) with a molecular mass of 74.5 g/mol, we can follow these steps:

### Step 1: Determine the mass of the metal M
The molecular mass of \( MCl \) is given as 74.5 g/mol. The atomic mass of chlorine (Cl) is approximately 35.5 g/mol.

To find the mass of the metal M, we can use the formula:
\[ \text{Mass of metal (M)} = \text{Molecular mass of } MCl - \text{Mass of Cl} \]
Substituting the values:
\[ \text{Mass of metal (M)} = 74.5 \, \text{g/mol} - 35.5 \, \text{g/mol} = 39.0 \, \text{g/mol} \]

### Step 2: Determine the equivalent mass of metal M
The equivalent mass of a substance is calculated using the formula:
\[ \text{Equivalent mass} = \frac{\text{Molar mass}}{n} \]
where \( n \) is the number of moles of reactive species (which can be the charge of the metal in this case).

For \( MCl \), chlorine (Cl) typically has a charge of -1 when it forms a chloride. Therefore, the metal M must have a charge of +1 to balance the charge in the compound \( MCl \). This means \( n = 1 \).

Now we can calculate the equivalent mass of metal M:
\[ \text{Equivalent mass of M} = \frac{39.0 \, \text{g/mol}}{1} = 39.0 \, \text{g} \]

### Final Answer:
The equivalent mass of the metal M is **39.0 g**.

---