1. Gypsum has the formula as CaSO₄.2H₂O. Hence, CaSO₄ is bound with two H₂O. CaSO₄ has 1 Ca atom, 1 S atom and 4 O atoms. 2H₂O have 4 H atoms and 2 O atoms.
Hence,
total Ca atoms = 1
total S atoms = 1
total O atoms = 4 + 2 = 6
total H atoms = 4
total number of atoms = 1 + 1 + 6 + 4 = 12
2. Cellulose has the formula as C₆H₇O₂(OH)₃. But there are 2 molecules. Hence, to find total atoms in each element, number of atoms should be multiplied by 2 .The elements of the cellulose are C, H, and O.
Hence,
total C atoms = 6 x 2 = 12
total O atoms = (2 + 3) x 2 = 10
total H atoms = (7 + 3) x 2 = 20
total number of atoms = 12 + 10 + 20 = 42
3. The formula of the antiperspirant is Al₂Cl(OH)₅. It has Al, Cl, O and H as the elements. Hence, the number of atoms in each element can be found as follows;
total Al atoms = 2
total Cl atoms = 1
total H atoms = 1 x 5 = 5
total O atoms = 1 x 5 = 5
total number of atoms = 2 + 1 + 5 + 5 = 13
