Question

Calculate the number of moles of sulfur atoms present in each of the following samples.

(a) 2.16 g of sodium sulfate
(b) 2.16 g of sodium sulfite
(c) 2.16 g of sodium sulfide
(d) 2.16 g of sodium thiosulfate, Na₂S₂O<sub>3

2-</sub> Calculate the percent by mass of each element in the following compounds.

(c) MnO₂

manganese	%
oxygen	%

Answer 1

(a) 2.16 g of sodium sulfate Na2SO4 = 142.04

mol Na2SO4 = mass/MW = 2.16/142.04 = 0.015206

mol of S = 1*0.015206 = 0.015206 mol of S

(b) 2.16 g of sodium sulfite Na2SO3 = 126.043

mol Na2SO3 = mass/MW = 2.16/126.043 = 0.01713

mol of S = 1*0.01713= 0.01713 mol of S

(c) 2.16 g of sodium sulfide Na2S = 78.0452

mol Na2S = mass/MW = 2.16/78.0452 = 0.02767

mol of S = 1*0.02767= 0.02767mol of S

(d) 2.16 g of sodium thiosulfate, Na2S2O3 = 158.11

mol Na2S = mass/MW = 2.16/158.11 = 0.01366

mol of S = 2*0.01366= 0.02732 mol of S

2.

Mn = 54.938045

Oxygen = 16

total mas s= 54.938045 +16*2 = 86.938045

% Mn = 54.938045/86.938045*100 = 63.1921%

% O = 16*2/86.938045*100 = 36.8078 %