Calculate:
a)percentage of hydrogen in ammonium sulphate
b)percentage composition of water present in washing soda
c)mass of oxygen present in 72 g of pure water

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Solution

Dear Student,

$a) Molecular formula of Ammonium Sulphate is ({NH}_{4})_{2} {SO}_{4} Molecular mass of : Ammonium sulphate ({NH}_{4})_{2} {SO}_{4} = 14.0 \times 2 + 1.00 \times 8 + 32.1 + 16.0 \times 4 = 132.1 g Hydrogen = 1.00 \times 8 = 8 g Now, % of hydrogen = \frac{Mass of hydrogen}{Mass of Ammonium Sulphate} \times 100 % of hydrogen = \frac{8}{132.1} \times 100 = 6.0560 % b) Molecular formula of washing soda is {Na}_{2} {CO}_{3} . 10 H_{2} O Molecular mass of : {Na}_{2} {CO}_{3} . 10 H_{2} O = (2 \times 23) + 12 + (3 \times 16) + 10 (2 \times 1 + 16) = 46 + 12 + 48 + 180 = 286 g water molecules = 10 \times (2 \times 1 + 16) = 180 g % of water in washing soda = \frac{The mass of water in wasing soda}{Molecular mass of washing soda} \times 100 % of water in washing soda = \frac{180}{286} \times 100 = 62.93 % c) Molecular formula of water is H_{2} O Molecular mass of H_{2} O = 2 \times 1 + 16 = 18 g Number of moles in 72 g of water = \frac{Mass}{Molae mass} = \frac{72}{18} = 4 mol Now, 1 mole of H_{2} O contains 16 g of O Therefore, 4 mol of H_{2} O contains 4 \times 16 = 64 g of oxygen$

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