Sulphate of an element is a compound that contains the element and sulphate ions. In this case, the compound contains 42.2% of the element.

To find the equivalent weight of the element, we need to determine the ratio of the element to the sulphate ion in the compound.

Let's assume the molecular formula of the compound is XSO4, where X represents the element.

We know that the molar mass of sulphate (SO4) is 48 g/mol. Since the equivalent weight of sulphate is given as 48, it means that one mole of sulphate contains one equivalent of sulphate.

To find the equivalent weight of the element, we need to determine the number of equivalents of the element in one mole of the compound.

To do this, we can calculate the molar mass of the compound, XSO4.

Let's assume the molar mass of the compound is M g/mol.

Since the compound contains 42.2% of the element, it means that 100 - 42.2 = 57.8% of the compound is sulphate.

Therefore, the molar mass of the element in the compound is 57.8% of M.

We can now set up the equation:

(57.8/100) * M = 48

Simplifying the equation:

0.578 * M = 48

Dividing both sides of the equation by 0.578:

M = 48 / 0.578

M ≈ 83.08 g/mol

So, the molar mass of the compound XSO4 is approximately 83.08 g/mol.

Since the molar mass of the element in the compound is 57.8% of the compound's molar mass, the molar mass of the element is approximately 0.578 * 83.08 = 47.98 g/mol.

Rounding this value to the nearest whole number, we get 48 g/mol.

Therefore, the equivalent weight of the element is 48 g/mol, which corresponds to option B) 35.0.