Gravimetric Analysis. Percentage (by mass) of Pb5Sb4S11

Gravimetric Analysis. Percentage (by mass) of Pb5Sb4S11

 

 

A 4.18-g geological sample, containing the mineral Boulangerite (Pb5Sb4S11) as the only lead-bearing compound, is subjected to chemical treatment in which the lead is quantitatively recovered as solid PbCl2. The mass of PbCl2 obtained is 2.44 g. What was the percentage (by mass) of Pb5Sb4S11 in the sample?

 

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PbCl2의 몰질량 = 278.11 g/mol 이므로,

PbCl2 2.44 g의 몰수를 계산하면,

2.44 g / (278.11 g/mol) = 0.0087735 mol

 

Pb5Sb4S11 : PbCl2 의 몰수 비 = 1 : 5 이므로,

Pb5Sb4S11의 몰수를 계산하면,

Pb5Sb4S11 : PbCl2 = 1 : 5 = ? : 0.0087735

? = 0.0087735 / 5 = 0.0017547 mol

 

Pb5Sb4S11의 몰질량 = 1875.76 g/mol 이므로,

Pb5Sb4S11 0.0017547 mol의 질량을 계산하면,

0.0017547 mol × (1875.76 g/mol) = 3.2914 g

 

질량 백분율 = (3.2914 g / 4.18 g) × 100 = 78.7%

 

 

답: 78.7%

 

 

한 번에 계산하면,

[(2.44 / 278.11 / 5 × 1875.76) / 4.18] × 100 = 78.7%