A volume of 20 ml of M K₂Cr₂O₇ solution is diluted to 200 ml. Twenty five millilitres of diluted solution is mixed with 50 ml of 4 M H₂SO₄ solution. Thirty millilitres of this mixture is diluted to 15

Question

A volume of 20 ml of M K₂Cr₂O₇ solution is diluted to 200 ml. Twenty five millilitres of diluted solution is mixed with 50 ml of 4 M H₂SO₄ solution. Thirty millilitres of this mixture is diluted to 150 ml. How many millilitres of 0.02 M H₂O₂ solution is needed to titrate 15 ml of the diluted solution?

TestHub · Accepted Answer

Taking the K₂Cr₂O₇ as 1 M: 20 ml holds 20 mmol; diluted to 200 ml → 0.1 M; 25 ml holds 2.5 mmol; mixed with 50 ml acid (75 ml) → 1/30 M; 30 ml (1 mmol) diluted to 150 ml → 1/150 M. 15 ml holds 0.1 mmol Cr₂O₇²⁻ = 0.6 meq. H₂O₂ (n = 2) is 0.04 N, so V = 0.6/0.04 = 15 ml - not listed, option (d).

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