1994 WAEC Chemistry Theory (a) When MgSO\(_4\).XH\(_2\)O crystals were exposed to the atmosphere for several days, three  was a...

(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)

(a)(i) The name of the phenomenon is Efflorescence

(ii) Another example is Na\(_2\)CO\(_3\).10H\(_2\)O.

(b) Molar mass of MgSO\(_4\) x H\(_2\)O = 2x

123 = 246 i.e. 24 + 32 + (4 x 16) + x (2X 1 + 16) = 246

120 + 18x = 246;

18x = 246 - 120;

18x = 126

x = \(\frac{126}{18}\)

x = 7

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