to weight BaCl₂ or Na₂SO₄

a) use a polythene bags and spring balance

b) use a watch glass and spring balance

c) use a polythene bags and physical balance

d) use a watch glass and physical balance

For this use a watch glass and physical balance. 

 First weigh the watch glass then put salt on the watch glass and weigh. 

 The weight of the salt = (weight of watch glass+ salt ) - ( weight of watch glass)