calcium in water is determined by the deposition of calcium oxalate. Precipitate

Question

calcium in water is determined by the deposition of calcium oxalate. Precipitated calcium oxalate was washed with excess of sulfuric acid and titrated with potassium permanganate. 200 ml of tap water consumed at such analysis 12 ml of 0,450 g / dm3 solution of potassium permanganate. calculate mass of calcium in 1 L of water calcium in water is determined by the deposition of calcium oxalate. Precipitated calcium oxalate was washed with excess of sulfuric acid and titrated with potassium permanganate. 200 ml of tap water consumed at such analysis 12 ml of 0,450 g / dm3 solution of potassium permanganate. calculate mass of calcium in 1 L of water

Explanation / Answer

The volume of water used = 200mL

In acidic solution the reaction will be

2MnO4+5CaC2O4 + 16H+2Mn2+ + 10CO2 + 8H2O + 5Ca+2

So they will react in 2:5 molar ratio

the mass of KMnO4 used = strength X volume = 0.450 X 12 / 1000 = 0.0054 grams

Moles of KMnO4 = Mass / mol wt = 0.0054 / 158 = 3.42 X 10^-5 moles

so moles of calcium oxalate = 5 X 3.42 X 10^-5 /2 moles = 8.55 X 10^-5 moles

mass = moles X atomic weight of Ca = 8.55 X 10^-5 X 40 = 3.42 X 10^-3 grams

This is present in 200mL

So mass in 1L = 3.42 X 1000 X 10^-3 / 200 = 17.1 X 10^-3 grams

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