Answer:
no. of water molecules associated to each molecule of
= 4
Explanation:
Mass of
before heating = 19.8 g
Mass of
after heating = 12.6 g
Difference in mass of
before and after heating
= 19.8 - 12.6 = 7.2 g
Difference in mass corresponds to mass of water driven out.
Molar mass of water = 18 g/mol
No. of moles of water = 
Mass of
obtained after heating is mass of anhydrous
.
Mass of anhydrous
= 12.6 g
Molar mass of
= 125.9 g/mol
No. of mol of anhydrous
= 
so,
0.1 mol of
have 0.4 mol of water
1 mol of
will have = 
Hence, no. of water molecules associated to each molecule of
= 4