# WBCHSE Class 11 Chemistry: Some Basic Concepts of Chemistry – Chhaya Publication

**Unit-1 (Some Basic Concepts of Chemisiry) of Chhaya Chemistry (xi) Part-1**

**Q1. The ratio of molecular masses of two substances \( A \) and \( B \) is \( 2: 3 \). If equal masses of these two substances be vaporised, the ratio of their volumes will be-**

**(A) \( 2: 1 \)**

**(B) \( 1: 2 \)**

**(C) \( 2: 3 \)**

**(D) \( 3: 2 \)**

**Q2. In natural chlorine gas the ratio of the number of moles of \( { }^{35} \mathrm{Cl} \) and \( { }^{37} \mathrm{Cl} \) is-**

**(A) \( 2: 3 \)**

**(B) \( 3: 1 \)**

**(C) \( 2: 1 \)**

**(D) \( 4: 3 \)**

**Q3. Naturally occurring boron (average molecular mass = 10.8 u ) has two isotopes \( { }^{10} \mathrm{~B} \) and \( { }^{11} \mathrm{~B} \). The percentage of \( { }^{10} \mathrm{~B} \) in the naturally occurring boron is-**

**(A) 20**

**(B) 23**

**(C) 31**

**(D) 27**

**Q4. 2.0 g of a mixture of \( \mathrm{Na}_{2} \mathrm{CO}_{3} \) and \( \mathrm{NaHCO}_{3} \) is heated strongly at \( 300^{\circ} \mathrm{C} \) till it attains constant mass. On cooling, the mixture attains a mass of 1.752 g . The percentage of \( \mathrm{Na}_{2} \mathrm{CO}_{3} \) in the initial mixture is-**

**(A) 50.2**

**(B) 66.4**

**(C) 56.8**

**(D) 43.8**

**Q5. 1.38 g of silver carbonate is heated strongly. On cooling, the mass of the residue becomes-**

**(A) 1.38 g**

**(B) 1.82 g**

**(C) 1.08 g**

**(D) 1.42 g**

**Q6. The equivalent weight of a metal is 9 . If the chloride of the metal has a vapour density of 66.8 , the atomic mass of the metal will be-**

**(A) 16.4**

**(B) 27**

**(C) 26.3**

**(D) 32.5**

**Q7. 3.04 g of a metal hydroxide is heated strongly till it decomposes completely to the corresponding metal oxide having a mass of 2.0 g . The equivalent weight of the metal is-**

**(A) 12.1**

**(B) 16.2**

**(C) 9.3**

**(D) 20.0**

**Q8. The percentage of nitrogen in an organic compound containing \( \mathrm{C}, \mathrm{H} \) and N is 20 . Lowest possible molecular mass of the compound will be-**

**(A) 80**

**(B) 70**

**(C) 60**

**(D) 48**

**Q9. A crystalline salt \( \left(\mathrm{M}_{2} \mathrm{SO}_{4} \cdot x \mathrm{H}_{2} \mathrm{O}\right) \) on heating loses \( 55.9 \% \) of its mass. If the atomic mass of \( M \) be \( 23 \) , the value of \( x \) will be-**

**(A) 7**

**(B) 8**

**(C) 9**

**(D) 10**

**Q10. Equivalent weight of A in the compound \( \mathrm{A}_{x} \mathrm{O}_{y} \) is ‘ \( E \). If atomic mass of \( A \) be ‘ \( a \) ‘ and \( y=1.5 x \), then which of the following relations will hold good-**

**(A) \( a=1.5 E \)**

**(B) \( E=0.2 \times a \)**

**(C) \( a=3 \times E \)**

**(D) \( E=0.4 \times a \)**

**Q11. Which of the following contains highest number of constituent particles-**

**(A) 0.36 g diamond**

**(B) \( 2.24 \mathrm{~L} \mathrm{CO}_{2} \) gas at STP**

**(C) 0.54 g ice**

**(D) \( 5 \mathrm{~L} \mathrm{H}_{2} \) gas at 1 atm pressure and \( 27^{\circ} \mathrm{C} \) temperature**

**Q12. The volume of 1.0 g of a gaseous substance (vapour density \( =14 \) ) at \( 27^{\circ} \mathrm{C} \) and 1 atm pressure is-**

**(A) 1 L**

**(B) 0.88 L**

**(C) 0.64 L**

**(D) 0.52 L**

**Q13. A metal (equivalent weight \( =65.6 \) ) has a specific heat of \( 0.13 \mathrm{~J} \mathrm{~g}^{-1} \mathrm{~K}^{-1} \). The atomic mass of the metal is-**

**(A) 492.0**

**(B) 459.2**

**(C) 196.8**

**(D) 216.9**

**Q14. 3.39 g of a mixture of \( \mathrm{CaCl}_{2} \) and \( NaCl \) is treated with excess of sodium carbonate solution and the entire amount of \( \mathrm{Ca}^{2+} \) ions is precipitated as \( \mathrm{CaCO}_{3} \). This \( \mathrm{CaCO}_{3} \), on being heated strongly produces 1.12 g of \( CaO \) . The percentage of \( NaCl \) in the initial mixture is-**

**(A) 30.49**

**(B) 31.27**

**(C) 32.74**

**(D) 34.51**

**Q15. A mixture of 224 L . (STP) of \( \mathrm{H}_{2} \) gas and 44.8 L (STP) of \( \mathrm{O}_{2} \) gas is exploded in a closed steel vessel. The amount of water produced is-**

**(A) 18 g**

**(B) 36 g**

**(C) 72 g**

**(b) 90 g**

**Q16. 100 mL x(\mathrm{M}) \mathrm{Ba}(\mathrm{OH})_{2} \) solution requires 500 mL of \( 0.82(\mathrm{M}) \mathrm{HCl} \) solution for its neutralisation. The amount of \( \mathrm{BaCO}_{3} \) (molecular mass \( =197.34 \) ) that will be precipitated if excess of \( \mathrm{CO}_{2} \) gas is passed through the above \( \mathrm{Ba}(\mathrm{OH})_{2} \) solution is-**

**(A) 80.90 g**

**(B) 40.45 g**

**(C) 101.27 g**

**(D) 112.34 g**

**Q17. 1 L of air at STP contains \( 9.375 \times 10^{-3} \mathrm{~mol} \) of \( \mathrm{O}_{2} \). So percentage of oxygen \( (V / V) \) in the air at STP is-**

**(A) 20**

**(B) 21**

**(C) 22**

**(D) 22.1**

**Q18. 11.81 g of a metal nitrate when heated strongly produces 0.5 g of the corresponding metal oxide. Equivalent weight of the metal is-**

**(A) 24**

**(B) 27**

**(C) 31.6**

**(D) 34**

**Q19. At a fixed temperature and pressure, 2.5 L of a sample of \( \mathrm{NH}_{3} \) is mixed with 1.2 L of HCl gas. The volume of the resultant mixture at the same temperature and pressure will be-**

**(A) 3.7 L**

**(B) 1.85 L**

**(C) 1.3 L**

**(D) 1.6 L**

**Q20. \(\mathrm{CO}_{2} \) produced by complete decomposition of 10 g of \( \mathrm{CaCO}_{3} \) is passed through a sodium carbonate solution containing \( 1 \mathrm{~mol} \mathrm{Na}_{2} \mathrm{CO}_{3} \) dissolved in it. Amount of \( \mathrm{NaHCO}_{3} \) produced will be-**

**(A) 8.4 g**

**(B) 10.2 g**

**(C) 12.8 g**

**(D) 16.8 g**

**Q21. Under a given set of condition 20 L dihydrogen and 15 L dioxygen are mixed together and allowed to react with each other to produce \( \mathrm{H}_{2} \mathrm{O} \) (steam). If the extent of reaction is only \( 50 \% \) of the theoretical value, the total volume of gas mixture obtained at the end of the reaction is-**

**(A) 15 L**

**(B) 20 L**

**(C) 25 L**

**(D) 30 L**

**Q22. 250 mL of an aqueous solution of oxalic acid requires 1.6 g NaOH for its complete neutralisation. Molar strength of the acid solution is-**

**(A) 0.05**

**(B) 0.07**

**(C) 0.08**

**(D) 0.1**

**Q23. \(100 \mathrm{~mL} 0.1(\mathrm{M}) \) solution of oxalic acid reacts completely with 20 mL of a solution of \( \mathrm{KMnO}_{4} \). Molarity of \( \mathrm{KMnO}_{4} \) solution \( \left(\mathrm{mol} \mathrm{L}^{-1}\right. \) ) is-**

**(A) 0.1**

**(B) 0.15**

**(C) 0.18**

**(D) 0.2**

**Q24. 0.38 of an organic compound \( (M=60) \) containing \( \mathrm{C}, \mathrm{H} \) and \( O \) on combustion produces \( 0.44 \mathrm{~g} \mathrm{CO}_{2} \) and \( 0.18 \ g \) \( \mathrm{H}_{2} \mathrm{O} \). The molecular formula of the compound is-**

**(A) \( \mathrm{CH}_{2} \mathrm{O} \)**

**(B) \( \mathrm{C}_{3} \mathrm{H}_{8} \mathrm{O} \)**

**(C) \( \mathrm{C}_{4} \mathrm{H}_{6} \mathrm{O} \)**

**(D) \( \mathrm{C}_{2} \mathrm{H}_{4} \mathrm{O}_{2} \)**

**Q25. 0.05 mol of a mixture of \( BaO \) and \( CaO \) requires 50 mL . of an aqueous solution of \( HCl \) for its complete neutralisation. The molar strength of the acid solution is-**

**(A) 1 (M)**

**(B) 2 (M)**

**(C) 2.5 (M)**

**(D) 3.0 (M)**

**Q26. In order to prepare 250 mL 2.0 (M) \( \mathrm{HNO}_{3} \) solution, 45 g of a sample of conc. \( \mathrm{HNO}_{3} \) is required. Percentage of \( \mathrm{HNO}_{3}(\mathrm{~W} / \mathrm{W}) \) in the sample of concentrated nitric acid is-**

**(A) 55**

**(B) 65**

**(C) 70**

**(D) 75**

**Q27. Mole fraction of water in an aqueous solution of glucose is 0.9 . Molality of the solution is-**

**(A) \( 4.38 \mathrm{~mol} \mathrm{~kg}^{-1} \)**

**(B) \( 6.17 \mathrm{~mol} \mathrm{~kg}^{-1} \)**

**(C) \( 5.06 \mathrm{~mol} \mathrm{~kg}^{-1} \)**

**(D) \( 5.29 \mathrm{~mol} \mathrm{~kg}^{-1} \)**

**Q28. The molarity and molality of an aqueous solution of urea are \( 2.05 \mathrm{~mol} \mathrm{~L}^{-1} \) and \( 2.0 \mathrm{~mol} \mathrm{~kg}^{-1} \) respectively. The density of the solution is-**

**(A) 1.00**

**(B) 1.09**

**(C) 1.15**

**(D) 1.21**

**Q29. The density of pure ethyl alcohol is \( 1.15 \mathrm{~g} \mathrm{~mL}^{-1} \). In order of prepare 100 mL of \( 0.5(\mathrm{M}) \) aqueous solution of ethyl alcohol, what volume of water be mixed with requisite amount of pure ethyl alcohol-**

**(A) 100 mL**

**(B) 98 mL**

**(C) 95 mL**

**(D) 90 mL**

**Q30. ‘ \( A \) ‘ and ‘ \( B \) ‘ are two different aqueous solutions of urea having percentage strength \( (W / W) \) of 10 and 20 respectively. If 100 g of solution ‘ \( A \) ‘ be mixed with 200 g of solution ‘ \( B \) ‘, the percentage strength \( (W / W) \) of the resulting mixture will be-**

**(A) 12.34**

**(B) 14.39**

**(C) 16.66**

**(D) 18.17**

**Q31. A and B are two different oxides of the metal M. Each gram of the oxide A contains 0.888 g metal and that of the oxide B contains 0.798 g metal. If the formula of the oxide A is \( \mathrm{M}_{2} \mathrm{O} \), the formula of the oxide B will be-**

**(A) \( \mathrm{MO}_{2} \)**

**(B) MO**

**(C) \( \mathrm{M}_{2} \mathrm{O}_{3} \)**

**(D) \( \mathrm{M}_{2} \mathrm{O} \)**

**Q32. The molecules of a compound contains \( 24 \% \) of sulphur as one of the elements. If each molecule of the compound contains three sulphur atoms, the molar mass of the compound will be-**

**(A) 240**

**(B) 320**

**(C) 360**

**(D) 400**

**Q33. The empirical formula of a compound is \( \mathrm{CH}_{2} \mathrm{O} \). Its vapour density is 2.813 times that of oxygen. Molecular formula of the compound is-**

**(A) \( \mathrm{C}_{4} \mathrm{H}_{8} \mathrm{O}_{4} \)**

**(B) \( \mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O}_{3} \)**

**(C) \( \mathrm{C}_{2} \mathrm{H}_{4} \mathrm{O}_{2} \)**

**(D) \( \mathrm{CH}_{2} \mathrm{O} \)**

**Q34. 100 mL . of a mixture of CO and \( \mathrm{CH}_{4} \) requires 80 mL of \( \mathrm{O}_{2} \) for its complete oxidation (all the volumes are measured at same temperature and pressure). The percentage of \( \mathrm{CH}_{4}(\mathrm{~V} / \mathrm{V} \) ) in the gas mixture is-**

**(A) 20**

**(B) 40**

**(C) 60**

**(D) 80**

**Q35. 90 mL of a mixture of nitrogen and nitric oxide is passed over heated copper and the volume of the resulting gas reduces to 60 mL . (All the volumes are measured at same temperatue and pressure). The percentage of nitric oxide \( (V / V) \) in the initial gas mixture is-**

**(A) 58.32**

**(B) 66.66**

**(C) 68.39**

**(D) 72.05**

**Q36. 100 mL of \( \mathrm{CO}_{2} \) is passed over red hot coke. The volume of the resulting gas mixture reduces to 60 mL . (at same temperature and pressure). Percentage of \( \mathrm{CO}_{2}(\mathrm{~V} / \mathrm{V}) \) in the resulting gas mixture is-**

**(A) 35**

**(B) 75**

**(C) 25**

**(D) 65**

**Q37. 50 mL . of propane gas is exploded with excess of oxygen. On cooling the volume of the gas mixture becomes 170 mL . Volume of oxygen present in the initial gas mixture is-**

**(A) 250 mL**

**(B) 260 mL**

**(C) 268 mL**

**(D) 270 mL**

**38. 1 mol of a gaseous hydrocarbon \( \left(\mathrm{C}_{x} \mathrm{H}_{y}\right) \) requires 6 mol of \( \mathrm{O}_{2} \) for its complete combustion and produces 4 mol \( \mathrm{CO}_{2} \). Thus the values of \( x \) and \( y \) are-**

**(A) \( x=2, y=4 \)**

**(B) \( x=4, y=8 \)**

**(C) \( x=3, y=6 \)**

**(D) \( x=2, y=2 \)**

**Q39. When 1.56 g of a metal hydroxide \( \mathrm{M}(\mathrm{OH})_{x} \) is heated strongly it produces 1.02 g of the corresponding metal oxide. Thus equivalent weight of M is-**

**(A) 9**

**(B) 12**

**(C) 23**

**(D) 31**

**Q40. The vapour density of a gas with respect to air is 1.528 . If the vapour density of air be 14.4 , the mass of 2 L of the gas under consideration is-**

**(A) 2.56 g**

**(B) 3.02 g**

**(C) 3.92 g**

**(D) 4.27 g**

**Q41. The nitride of a metal \( M \) has the formula \( \mathrm{M}_{3} \mathrm{~N}_{x} \). It contains \( 28 \% \) nitrogen ( \( W / W \) ). Equivalent weight of M is-**

**(A) 9**

**(B) 12**

**(C) 14**

**(D) 18**

**Q42. 1 mol of an element ‘ \( X \) ‘ reacis with \( 1 \mathrm{~mol} \mathrm{O}_{2} \) gas to form 1 mol of a gaseous oxide. If vapour density of the oxide be 32 , the element ‘ X ‘ is-**

**(A) N**

**(B) P**

**(C) S**

**(D) C**

**Q43. Anhydrous sulphate of a metal M contains \( 15.8 \% \) of the metal. If specific heat of the metal be \( 0.237 \mathrm{cal} \mathrm{g}^{-1} \mathrm{~K}^{-1} \), the formula of the salt is-**

**(A) \( \mathrm{MSO}_{4} \)**

**(B) \( \mathrm{M}_{2} \mathrm{SO}_{4} \)**

**(C) \( \mathrm{M}_{2}\left(\mathrm{SO}_{4}\right)_{3} \)**

**(D) cannot be predicted**

**Q44. The vapour density of a gas mixture consisting of \( \mathrm{NO}_{2} \) and \( \mathrm{N}_{2} \mathrm{O}_{4} \) is 38.3 . Number of moles of \( \mathrm{NO}_{2} \) in 100 mol mixture is-**

**(A) 31.26**

**(B) 33.48**

**(C) 36.42**

**(D) 41.73**

**Q45. How many mL of \( 9.52(\mathrm{M}) \mathrm{HNO}_{3} \) will be required to dissolve 3.975 g of cupric oxide-**

**(A) 25.8**

**(B) 20.2**

**(C) 14.5**

**(D) 10.5**

**Q46. 7.75 mL of a certain HCl acid solution reacts completely with 3.76 g of \( \mathrm{CaCO}_{3} \). If density of the HCl acid solution be \( 1.18 \mathrm{~g} \mathrm{~mL}^{-1} \), the percentage strength ( \( W \) / W) of this solution will be-**

**(A) 25.1**

**(B) 30.0**

**(C) 36.5**

**(D) 41.7**

**Q47. The percentage strength ( \( W / W \) ) of a solution of HCl is 25. \( W \) gram of this solution reacts with excess of \( \mathrm{CaCO}_{3} \) to produce 2.24 L of \( \mathrm{CO}_{2} \) (at STP). So the value of \( W \) is-**

**(A) 25**

**(B) 28.3**

**(C) 29.2**

**(D) 32.7**

**Q48. Number of moles of \( \mathrm{O}_{2} \) required for complete combustion of 1 mol of the alkyne \( \mathrm{C}_{n} \mathrm{H}_{2 n-2} \) is-**

**(A) \( \frac{3}{2} n \)**

**(B) \( \frac{3}{2} n+1 \)**

**(C) \( \left(\frac{3 n-1}{2}\right) \)**

**(D) \( \frac{3}{2} n+2 \)**

**Q49. \( \mathrm{MnO}_{2} \) reacts with HCl to form \( \mathrm{MnCl}_{2}, \mathrm{H}_{2} \mathrm{O} \) and \( \mathrm{Cl}_{2} \). Thus the amount of \( \mathrm{Cl}_{2} \) formed when \( 1 \mathrm{~g} \mathrm{MnO}_{2} \) reacts with 1 g HCl is given by-**

**(A) 0.6257 g**

**(B) 0.5819 g**

**(C) 0.5369 g**

**(D) 0.4863 g**

**Q50. 5 g of an impure sample of NaCl is treated with excess of \( \mathrm{AgNO}_{3} \) solution. 9.812 g of AgCl is thus precipitated. So the purity (\%) of the sample of NaCl is-**

**(A) 60.2**

**(B) 75.0**

**(C) 80.0**

**(D) 82.4**

**Thank You**