Question

CuS contains 66.6% Cu, CuO contains 79.9% Cu & SO3 contains 48% S. Show that these data illustrates law of reciprocal proportion .

Answer 1

In copper sulphides: Cu : S mass ratio is 66.6 : 33.4 .

In sulphur trioxide: O : S (O:S) mass ratio is 60:40 .

Now in CuS: 33.4 parts of sulphur combines with 66.6 parts of Cu.

40.0 parts of sulphur combines with 66.6 x 40/33.4 = 79.8 parts of Cu.

Now the ratio of masses of Cu and O which combines with same mass (40 parts) of sulphur separately is 79.8:60 …(1)

Cu : O ratio by mass in CuO is 79.9: 20.1 …(2)

ratio 1 : ratio 2 = 79.8× 20.1

60. × 79.9 = 1:3

Which is simple whole number ratio, hence law of reciprocal proportion is proved.