A sample is a mixture of Mohr's salt and (NH4)2SO4. A 0.5 gram sample of the mixture gave a precipitate of 0.75 grams of Barium sulphate. Calculate the percentage composition of the mixture. What weight of Fe2O3 be obtained if 0.2 grams of the mixture were ignited in air?

Dear Student,

When the mixture of mohr's salt and ammonium sulphate reacts with barium chloride, only ammonium sulphate reacts to form barium sulphate. The reaction being:

NH4SO4 + BaCl2  BaSO4 + 2NH4ClFrom the equation, it can be seen that;For 1 mole of BaSO4, 1 mole of NH4SO4 is required.i.e. For 233.38g of BaSO4, 132.14g of NH4SO4 is required.According to the question, 0.75 gm of BaSO4 was formedSo, For  0.75g of BaSO4, 132.14233.38× 0.75g of NH4SO4 is required=0.42g of NH4SO4 is requiredsince the mixture was 0.5 g,amount of mohr salt = 0.5 - 0.42 = 0.08gpercentage composition of mohr's salt = 0.080.5×100 = 16%percentage composition of  NH4SO4 = 100 - 16 = 84%
 

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