Copper sulphate is soluble in water.

Explanation

In demethyl ether, the size of the methyl group is smaller as compared with that of ethyl group in diethyl ether. Therefore , the extent of hydrogen bonding in he molecules of dimethyl ether and water is large compared with molecules of diethyl ether . As a result dimethyl ether is completely soluble or miscible in water while diethyl ether is soluble only to small extent.