0.84 gms, of metal hydride contains 0.04 gms of hydrogen. The equivalent wt. of metal is.

Options

A. 80
B. 40
C. 20
D. 60

Answer

To find the equivalent weight of the metal in the metal hydride, we can follow these steps:

### Step 1: Determine the mass of the metal
Given:
- Mass of metal hydride = 0.84 g
- Mass of hydrogen in the hydride = 0.04 g

To find the mass of the metal, we subtract the mass of hydrogen from the mass of the metal hydride:

\[ \text{Mass of metal} = \text{Mass of metal hydride} - \text{Mass of hydrogen} \]

\[ \text{Mass of metal} = 0.84 \, \text{g} - 0.04 \, \text{g} = 0.80 \, \text{g} \]

### Step 2: Calculate the equivalent weight of hydrogen
The equivalent weight of an element is given by the formula:

\[ \text{Equivalent weight} = \frac{\text{Atomic mass}}{\text{Valence}} \]

For hydrogen:
- Atomic mass of hydrogen (H) = 1 g/mol
- Valence of hydrogen in metal hydride = 1 (since it is in the form of hydride, H^-)

Thus, the equivalent weight of hydrogen is:

\[ \text{Equivalent weight of hydrogen} = \frac{1}{1} = 1 \, \text{g/equiv} \]

### Step 3: Relate the mass of metal to the mass of hydrogen
In the reaction, the mass of the metal that reacts with hydrogen can be related to the equivalent weights. The equivalent weight of the metal can be calculated using the ratio of the mass of the metal to the mass of hydrogen:

\[ \text{Equivalent weight of metal} = \frac{\text{Mass of metal}}{\text{Mass of hydrogen}} \times \text{Equivalent weight of hydrogen} \]

Substituting the values we have:

\[ \text{Equivalent weight of metal} = \frac{0.80 \, \text{g}}{0.04 \, \text{g}} \times 1 \, \text{g/equiv} \]

\[ \text{Equivalent weight of metal} = 20 \, \text{g/equiv} \]

### Final Answer
The equivalent weight of the metal is **20 g/equiv**.

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