Question

A piece of rock salt weighs 108.2g in air and 48.2g in saturated brine of relative density 1.2. What is the relative density of rock salt?

Answer 1

Weight of brine displaced is the buoyancy force . If 108.2g of salt are pushing down but we record a weight of 48.2g then displaced brine pushed back with the weight of 60g. 

We are told that density of brine is 1.2 

We know that d = m/v 

So, 1.2g/cc = 60g/ x 

x = 60 g/1.2g/cc 

x = 50 cc 

So that has to be the volume of the rock salt. 

Again, we know that 

d = m/v 

d = 108.2/ 50cc 

d = 2.164