Law of reciprocal proportion

source : Hemantmore.org.in

## Law of reciprocal proportion-

### Question 2 ) Copper sulphide contains 66.5 % Cu, copper oxide contains 79.9 % Cu and sulphur trioxide contains 40% Sulphur.Show that the data illustrates the law of reciprocal proportions.

### Solution)

source : Hemantmore.org.in

*In Copper sulphide ,*

*mass of Cu = 66.5 gm*

*mass of sulphur = 100 – 66.5 = 33.5 gm*

*In Copper oxide,*

*mass of Cu = 79.9 gm*

*mass of oxygen = 100 – 79.9 = 20.1 gm*

*Let us fix the mass of Cu to 1 gm.*

*In Copper sulphide ,*

*66.5 gm Cu combine with sulphur = 33.5*

*1 gm Cu combine with sulphur = 33.5 / 66.5 = 0.5 gm*

*In , Copper oxide ,*

*79.9 gm of Cu combine with oxygen = 20.1*

*1 gm of Cu combine with oxygen = 20.1 / 79.9 = 0.25 gm*

*The ratio of masses of sulphur and oxygen which combine with the fixed mass of Cu ( 1.0 gm) is ,*

*0.50 : 0.25 or 2 : 1*

*In SO3 ,*

*mass of sulphur = 40 gm*

*mass of oxygen = 100 – 40 = 60 gm*

*The ratio of masses of sulphur and oxygen in SO _{3} is ,*

*40 : 60 = 2 : 3*

*Now comparing the ratio, 2 / 1 : 2/3= 3 : 1*

*This is a simple whole number ratio.*

*Hence given data follows law of reciprocal proportion.*

### Question 3) Illustrate the law of reciprocal proportions from the following data, KCl contains 52% potassium , KI contains 23.6% potassium and ICl contains 78.2 % iodine .

### Solution )

*In KCl ,*

*mass of K = 52.0 gm*

*mass of Cl = 100 – 52.0 = 48.0 gm*

*In KI ,*

*mass of K = 23.6 gm*

*mass of I = 100 – 23.6 = 76.4 gm*

*Let us fix the mass of K to 1 gm.*

*In KCl ,*

*52.0 gm K combine with Cl = 48*

*1 gm K combine with Cl = 48 / 52 = 0.92 gm*

*In KI ,*

*23.6 gm of K combine with I = 76.4 gm*

*1 gm of K combine with I = 76.4 / 23.6 = 3.24 gm*

*The ratio of masses of Cl and I which combine with the fixed mass of K ( 1.0 gm) is ,*

*0.92 : 3.24 or 1 : 3.5*

*In ICl ,*

*mass of I = 78.2 gm*

*mass of Cl = 100 – 78.2 = 21.8 gm*

*The ratio of masses of Cl and I in ICl is ,*

*21.8 : 78.2 = 1 : 3.5*

*Now comparing the ratio, 1/ 3.5 : 1/3.5= 1 : 1*

*This is a simple whole number ratio.*

*Hence given data follows law of reciprocal proportion.*