The vapour density of a tribasic acid is x. The equivalent mass of that acid is

Options

A. `(x)/(3)`
B. `x-3`
C. `(2x)/(3)`
D. `2x-3`

Explanation

To determine the equivalent mass of a tribasic acid given its vapor density (x), we can follow these steps:

### Step 1: Understand the relationship between vapor density and molar mass
The vapor density (VD) of a substance is related to its molar mass (M) by the formula:
\[ \text{Vapor Density} = \frac{\text{Molar Mass}}{2} \]
From this, we can express the molar mass in terms of vapor density:
\[ \text{Molar Mass} = 2 \times \text{Vapor Density} \]

### Step 2: Substitute the given vapor density
Given that the vapor density of the tribasic acid is \( x \), we can substitute this into the equation:
\[ \text{Molar Mass} = 2x \]

### Step 3: Determine the n-factor for a tribasic acid
A tribasic acid can donate three protons (H⁺ ions) when it dissociates in solution. Therefore, the n-factor (number of moles of H⁺ ions that can be produced) for a tribasic acid is 3.

### Step 4: Calculate the equivalent mass
The equivalent mass (E) of the acid can be calculated using the formula:
\[ \text{Equivalent Mass} = \frac{\text{Molar Mass}}{\text{n-factor}} \]
Substituting the values we have:
\[ \text{Equivalent Mass} = \frac{2x}{3} \]

### Final Answer
Thus, the equivalent mass of the tribasic acid is:
\[ \text{Equivalent Mass} = \frac{2x}{3} \]

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