Some Basic Concepts of Chemistry

A mixture of CaCl₂ and NaCl weighing 4.44 g is treated with sodium carbonate solution to precipitate all the calcium ions as calcium carbonate. The calcium carbonate so obtained is heated strongly to get 0.56 g of CaO. The percentage of NaCl in the mixture is (atomic mass of Ca = 40)

• 75

• 31.5

• 40.2

• 25

The rms velocity of hydrogen is $\sqrt{7}$ times the rms velocity of nitrogen. If T is the temperature of the gas, which of the following is true?

• ${\mathrm{T}}_{{\mathrm{H}}_2} = \sqrt{7 } {\mathrm{T}}_{{\mathrm{N}}_2}$

• ${\mathrm{T}}_{{\mathrm{N}}_2} = {\mathrm{T}}_{{\mathrm{H}}_2}$

• ${\mathrm{T}}_{{\mathrm{N}}_2} = \sqrt{7} {\mathrm{T}}_{{\mathrm{H}}_2}$

• ${\mathrm{T}}_{{\mathrm{N}}_2} = 2{\mathrm{T}}_{{\mathrm{H}}_2}$

The vapour pressures of two liquids A and B in their pure states are in the ratio of 1: 2. A binary solution of A and B contains A and B in the mole proportion of 1 : 2. The mole fraction of A in the vapour phase of the solution will be

• 0.2

• 0.25

• 0.52

• 0.33

10 g of a mixture of BaO and CaO requires 100 cm³ of 2.5 M HCl to react completely. The percentage of calcium oxide in the mixture is approximately (Given: molar mass of BaO = 158)

• 52.6

• 55.1

• 44.9

• 47.4

0.30 g of an organic compound containing C, H and oxygen on combustion yields 0.44 g of CO₂ and 0.18 g of H₂O. If one mole of compound weighs 60, then molecular formula of the compound is

• CH₂O

• C₃H₈O

• C₄H₆O

• C₂H₄O₂

The vapour pressures of pure liquids A and B are 400 and 600 mm Hg, respectively at 298 K. On mixing the two liquids, the sum of their initial volumes is equal to the volume of the final mixture. The mole fraction of liquid B is 0.5 in the mixture. The vapour pressure of the final solution, the mole fractions of components A and B in vapour phase, respectively are:

• 500 mm Hg, 0.4, 0.6

• 450 mm Hg, 0.4, 0.6

• 500 mm Hg, 0.5, 0.5

• 450 mm Hg, 0.5, 0.5