Answer:
20.93%
Explanation:
The percent by mass (%mass) of water in the following compound can be calculated thus:
%mass of H2O = mass of 2H2O/mass of compound × 100
Where;
Ca = 40
S = 32
O = 16
H = 1
Hence, the molar mass of CaSO4•2H20 = 40 + 32 + 16(4) + 2{ 1(2) + 16}
= 40 + 32 + 64+ 2{18}
= 172g/mol
Molar mass of 2H2O = 2{2 + 16}
2(18)
= 36g/lol
Therefore, the percent by mass of 2H2O in CaSO4•2H20 is as follows:
36/172 × 100
= 0.2093 × 100
= 20.93%
