प्रतिशत संघटन Percentage composition | Chap 01 | Part 05 | Class 11th || Some basic concepts

1.5 g of a mixture containing As_2O_5 , Na_2HAsO_3 , and some inert impurities is dissolved in water, and the solution is kept neutral by adding excess of NaHCO_3 . The solution when titrated with 0.1 M I_2 required 35.0 nL of it for complete titration. The solution is then acidified and excess of KI is added to it. The I_2 liberated required 35.0mL of 0.3 M Na_2S_2O_3 solution for complete titration. Find the percentage composition of the mixture (Atomic mass of As is 75, Na is 23 and O is 16.)

A sample of 0.50 g of an organic compound was treated according to Kjeldahl's method. The ammonia evolved was absorbed in 50 mL of 0.5 M H_(2)SO_(4) . The residual acid required 60 mL of 0.5 M solution of NaOH for neutralization. Find the percentage composition of nitrogen in the compound. Strategy: Step 1 . Convert molarity into normality using the relation Normality (N) = n xx Molarity (M) where n factor is either the acidity of base or basicity of acid. Step 2 . Calculate the milliequivalents of NaOH which is equal to the milliequivalents of unreacted H_(2)SO_(4) . Step 3 . Calculate the milliequivalents of total H_(2)SO_(4) and subtract the milliequivalents of unreacted H_(2)SO_(4) to get the milliequivalents of NH_(3) evolved. Step 4 . Calculate the equivalents of NH_(3) , moles of NH_(3) , and moles of N . Step 5 . Calculate the mass of N in the organic compound. Step 6 . Finally, calculate % of N or directly apply Eq. (13.8) or (13.9) to get the % of N in the organic compound.

Arun has prepared 0.01% (by mass) solution of sodium chloride in water. Which of the following correctly represents the composition of the solutions? (a) 1.00 g of NaCl + 100 g of water (b) 0.11 g of NaCl + 100 g water (c) 0.01 g of NaCl + 99.99 g of water (d) 0.10 g of NaCl + 99.90 g of water