Gravimetric Analysis

Question

In gra‎vimetric det‎ermination of Phospohrus, 0.2161 g Mg₂P₂O₄ was obtai‎ned after preciptation of 0.3516 g det‎ergent sample. Cal‎culate the perce‎ntage of the phosphorus.

Answer 1

Atomic mass P = 30.97 g / mol

Atomic mass Mg = 24.31 g/mol

Molar mass Mg₂P₂O₄ = 174.6 g/mol

% by mass Mg in Mg₂P₂O₄ = (2x24.31 g) / (174.6 g) x 100% = 27.85% Mg

mass of Mg in 0.2161 g Mg₂P₂O₄ = 27.85% x 0.2161 g = 0.0602 g Mg

% Mg in original sample = 0.0602 g / 0.3516 g (x100%) = 3.700 %