50 g of a sample of Ca ( OH ) 2 is dissolved in 50 ml of 0.5 N HCl solution. The excess of HCl was back titrated with 0.3 N NaOH . The volume of NaOH used was 20cc. Calculate the percentage purity o

Question

50 g of a sample of Ca ( OH ) 2 ​ is dissolved in 50 ml of 0.5 N HCl solution. The excess of HCl was back titrated with 0.3 N NaOH . The volume of NaOH used was 20cc. Calculate the percentage purity of Ca ( OH ) 2 ​ (M Ca = 40, Mo = 16, M H = 1)

TestHub · Accepted Answer

Number of equivalents of Ca(OH)₂ = ( 50 × 0.5 × 1 0 − 3 ) − ( 20 × 1 0 − 3 × 0.3 ) Number of moles of Ca(OH)₂ = 2 ( 25 − 6 ) × 1 0 − 3 ​ = 9.5 × 1 0 − 3 Mass of Ca(OH)₂ = ( 9.5 × 1 0 − 3 ) × 74 g % purity = 50 9.5 × 1 0 − 3 × 74 ​ × 100 = 1.4%

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