(a) When MgSO\(_4\).XH\(_2\)O… | Chemistry

Question 1 Report

(a) When MgSO\(_4\).XH\(_2\)O crystals were exposed to the atmosphere for several days, three was a loss in mass

(i) What name is given to this phenomenon?

(ii) Give another example of a compound that exhibits this phenomenon

(b) If 0.50 mole of MgSO\(_4\).XH\(_2\)O has a mass of 123g. calculate the value of X. (H = 1, O = 16, Mg = 24, S = 32)

Answer

Answer Details

(a)(i) The loss in mass of a hydrated crystal (loss of water of crystallisation) to the atmosphere is called efflorescence.

(ii) Another example: sodium trioxocarbonate(IV) decahydrate, Na₂CO₃·10H₂O (washing soda).

(b) Finding X in MgSO₄·XH₂O

Molar mass of the hydrate \( = \dfrac{\text{mass}}{\text{moles}} = \dfrac{123}{0.50} = 246\ \text{g mol}^{-1} \)

Molar mass of anhydrous MgSO₄ \( = 24 + 32 + (4\times16) = 120\ \text{g mol}^{-1} \)

Mass of water \( = 246 - 120 = 126\ \text{g} \)

\[ X = \frac{126}{18} = \mathbf{7} \]

The compound is MgSO₄·7H₂O.

(a) When MgSO\(_4\).XH\(_2\)O crystals were exposed to the atmosphere for several days, three was a loss in mass (i) What name is given to this phenomenon? ...