Calculate the percentage composition of:
Alumina `(Al_(2) O_(3)`, potassium oxide `(K_(2) O)`, and silcia `(SiO_(2))` in the sample of clay `(Al_(2) O_(3). K_(2) O. 6SiO_(2))`.
b. Potassium sulphate `(K_(2) SO_(4))`. Aluminium sulphate, and water of crystallisation in the simple of potash alum, `(K_(2) SO_(4). Al_(2) (SO_(4))_(3). 24H_(2) O)`.

Explanation

Molar mass of `Al_(2) O_(3). K_(2) O. 6 SiO_(2)`
`= (2 xx 27 + 3 xx 16) + (2 xx 39 + 16) + 6 (28 + 2 xx 16)`
`= 102 + 94 + 360 = 556 g`
`Mass % of Al_(2)O_(3) = (102)/(556) xx 100 = 18.35%`
Mass % of `K_(2) O = (94)/(556) xx 100 = 16.90 %`
Mass % of `SiO_(2) = (360)/(556) xx 100 = 64.75%`
b. Molar mass of `K_(2) SO_(4) Al_(2) (SO_(4))_(3) 23 H_(2) O`
`= (2 xx 39 + 32 + 64) + [2 xx 27 + 3 (32 + 64) + 24 xx 18]`
`= 174 + 342 + 432 = 948 g`
Mass % of `K_(2) SO_(4) = (174)/(948) xx 100 = 18.35%`
Mass % of `Al_(2) (SO_(4))_(3) = (342)/(948) xx 100 = 36.07 %`
Mass % of `H_(2) O = (432)/(948) xx 100 = 45.56 %`
c. Molar mass of `4 (SO_(4)^(2-)) = 4(32 + 64) = 384 g`
Mass % of `SO_(4)^(2-) = (384)/(948) xx 100 40.50%`