Question 6:
Calcium sulfate dihydrate is a chemical compound with the formula CaSO4•2H2O, which means it contains one calcium, one sulfur, four oxygen, and two water molecules. The chemical formula of sodium carbonate is Na2CO3, which means it contains 2 sodium, one carbon and 3 oxygen atoms.
The compound you mentioned contains 4.8 moles of sodium carbonate (Na2CO3) which is not a component of Calcium sulfate dihydrate(CaSO4•2H2O) thus the question is invalid.
Question 7:
To find the number of moles of water in the sample, you need to use the molar mass of water. The molar mass of water is 18.02 g/mol.
1.17 g of water / 18.02 g/mol = 0.0649 moles of water
So, the sample contains 0.0649 moles of water.
Sodium acetate trihydrate is chemical compound with the formula CH3COO-Na.3H2O which means it contains one sodium, 2 acetate and 3 water molecules.