In an experiment, 4 90 g of copper oxide was obtained from 3 92 g of copper In another - Science - Atoms and Molecules

Question

In an experiment, 4 90 g of copper oxide was obtained from 3 92
g of copper In another experiment, 4 55g of copper oxide gave, on
reduction, 3 64 g of copper Show with the help of calculations that
these figures verify the law of constant proportions

Mohit Gupta · Accepted Answer

The law
of constant proportion is also known as the law of
definite proportion This law states that in a compound,
the elements are always present in definite proportions by mass The
reaction between copper and oxygen leading to the formation of
copper oxide is written as follows

2Cu +
O2
â†’ 2CuO

As per
the given data, 4 90 g of copper oxide was obtained from 3 92 g of
copper Therefore, the percentage of copper in 4 90g of CuO will
be

= (mass
of copper / mass of CuO) X 100

= (3 92
/ 4 9) X 100

= 80
%

As per
the data of the second experiment, 3 64g of copper is obtained from
4 55g of CuO So, percentage of copper in this sample of copper
oxide will be

= (mass
of copper / mass of CuO) X 100

= (3 64
/ 4 55) X 100

= 80
%

Thus,
we see that percentage of copper in both samples of CuO is the same
This means that copper and oxygen always combine in a fixed ratio
by mass to form CuO Thus the law of constant proportions is
satisfied here

In an experiment, 4.90 g of copper oxide was obtained from 3.92 g of copper. In another experiment, 4.55g of copper oxide gave, on reduction, 3.64 g of copper. Show with the help of calculations that these figures verify the law of constant proportions.