CBSE Class 11 Chemistry Basic Concepts Worksheet

Question. The molecular formula of the compound formed by the combination of elements 13A27 and 8 B 16 is:
(A) AB
(B) A₂B
(C) AB₂
(D) A₂B₃
Answer. D

Question. 1.204 × 10²⁴ molecules are present in a sample of methane. What will be its weight (in grams)?
(A) 32
(B) 24
(C) 16
(D) 12
Answer. A

Question.Na₂ CO₃ + 2HCl → 2 NaCl + CO₂ + H₂O
According to the above reaction, how many grams of Na₂CO₃ will be needed to obtain 11.2 litre CO₂ ?
(A) 51
(B) 53
(C) 83
(D) 106
Answer. B

Question. The empirical formula of a compound is CH₂. If its vapour density be 21, the molecular formula of this compound will be 
(A) C₂H₄
(B) C₃H₆
(C) C₄H₈
(D) C₅H₁₀
Answer. B

Question. A gas X is five times heavier than hydrogen while the other gas Y is two times heavier than X.The molecular weight of Y will be -
(A) 2.5
(B) 5
(C) 20
(D) 10
Answer. C

Question. The mass of a platinum wire is W gm. On heating it red hot in air and cooling, its mass remains W gm.
This observation proves
(A) Law of definite proportion
(B) Law of multiple proportion
(C) Law of conservation of mass
(D) None of these
Answer. D

Question. If the quantity of metal in a metallic oxide is 60% then its equivalent weight is 
(A) 1/5 of molecular weight
(B) 1/2 of molecular weight
(C) 3/2 of molecular weight
(D) 3/5 of molecular weight
Answer. D

Question. The normality of 0.3 M phosphoric acid is
(A) 0.1
(B) 0.9
(C) 0.3
(D) 0.6
Answer. B

Question. Mg has three natural isotopes whose isotopic masses and relative abundances are respectively 23.98(78.60%), 24.98 (10.11%) and 25.98 (11.29%) The atomic mass of Mg will be -
(A) 23.42
(B) 24.31
(C) 24.95
(D) 23.95
Answer. B

Question. One Litre of a gas at STP has mass equal to 1.25 g. The gas is - 
(A) H₂
(B) O₂
(C) N₂
(D) CO₂
Answer. C

Question. 100 gm of an aq. solution of sugar contains 40% sugar by mass. How much water hould be evaporated to get 50% sugar solution by mass ? 
(A) 10 g.
(B) 20 g.
(C) 0.0 g.
(D) 40 g.
Answer. B

Question. The percentage by mass of cation is ammonium chromate will be (At. mass of Cr = 52, N = 14, O = 16).
(A) 13.4%
(B) 30.4%
(C) 25.7%
(D) 23.7%
Answer. D

Question. Empirical formula of a compound is CH₂O. Its vapor density is 30. The compound is :
(A) Ethanoic acid
(B) Methyl Methanoate
(C) Ethanal
(D) Both (A) and (B)
Answer. D

Question. 2 litre of hydrogen and 1.2 litre of chlorine are mixed and exploded.The composition by volume of the resultant mixture will be- 
(A) 0.8 litre of hydrogen and 2.4 litre of chlorine
(B) 0.8 litre of hydrogen and 2.4 litre of hydrogen chloride
(C) 2.4 litre of hydrogen chloride
(D) 0.8 litre of chlorine and 24 litre of hydrogen chloride
Answer. B

Question. 1.35 gm ‘X’ element is completely converted to 1.88 gm compound ‘XO’. What is the atomic weight of ‘X’ ?
(A) 20.32
(B) 40.75
(C) 16.25
(D) 56.10
Answer. B

Question. The mass of oxygen required for the completecombustion of 1.6 Kg of methane is :
(A) 6.4 Kg
(B) 3.2 Kg
(C) 1.2 Kg
(D) 12.8 kg
Answer. A

Question. One mole of magnesium nitride on reaction with excess of water gives : 
(A) One mole of ammonia
(B) Two moles of ammonia
(C) One mole of nitric acid
(D) Two moles of nitric acid
Answer. B

Question. When 2 moles of N₂ gas and 9 moles of H₂ gas are mixed and reaction is completed to from NH₃ gas then reaction mixture will contain:
(A) 11 moles of NH₃
(B) 4 moles of NH₃ + 3 moles of H₂
(C) 6 moles of NH₃ + 3 moles of H₂
(D) 2 moles of NH₃ + 1 mole of N₂
Answer. B

Question. Under the same conditions of temperature and pressure, 1L of oxygen gas was mixed with 1L of carbon dioxide gas. The mass ratio of the gases in the mixture will be 
(A) 1 : 1
(B) 8 : 11
(C) 11 : 8
(D) 16 : 44
Answer. B

Question. 10 gm H₂ and 64 gm O₂ were taken in a sealed vessel and exploded. The amount of water produced in the reaction was : 
(A) 3 mole
(B) 4 mole
(C) 1 mole
(D) 2 mole
Answer. D

Question. A sample of MgCO₃ contains 3.01 × 10²³ Mg²⁺ ions and 3.01 × 10²³ CO₃^2– ions. The mass of the sample is :
(A) 42 mg
(B) 84 g
(C) 0.042 kg
(D) 42 mol
Answer. C

Question. What mass of hydrogen and oxygen will be produced on complete electrolysis of 18g of water ?
(A) 2g hydrogen and 32g oxygen
(B) 2g hydrogen and 16g oxygen
(C) 4g hydrogen and 32g oxygen
(D) 4g hydrogen and 14g oxygen
Answer. B

Question. Number of molecules in 14 g of carbon monoxide is 
(A) 12.044 × 10²³
(B) 6.022 × 10²³
(C) 3.011 × 10²³
(D) 1.5050 × 10²³
Answer. C

Question. Hydrogen was passed over heated 2.0 gm copper oxide till only copper was left. The mass of copper obtained was 1.6 gm. The percentage of oxygen in copper oxide is :
(A) 80%
(B) 60%
(C) 40%
(D) 20%
Answer. D

Question. Which of the following molecule has an atomicity of four : 
(A) H₂O
(B) NH₃
(C) CH₄
(D) CO₂
Answer. B

Question. One mole of CO₂ means : 
(A) 4.4 gm CO₂
(B) 2.24 litres gas at STP
(C) 6.022 × 10²³ molecules of CO₂
(D) 22 gm CO₂
Answer. C

Question. How many grams of oxygen are required to burn 40 gm of sulphur ? S(s) + O₂(g) → SO₂(g)
(A) 4.0 gm
(B) 40.0 gm
(C) 400 gm
(D) 80 gm
Answer. B

Question. When iron filings are heated in a steam of dry hydrogen chloride, the compound formed is FeClx where x is
(A) 1
(B) 2
(C) 3
(D) 4
Answer. B

Question. The solubility of a substance S in water is 28.6% (mass by volume) at 50º C. When 50 mL of its saturated solution at 50ºC is cooled to 40ºC, 2.4 g of solid S separates out.The solubility of S in water at 40ºC (mass by volume) is : 
(A) 2.4 %
(B) 11.9%
(C) 26.2%
(D) 23.8%
Answer. D

Question. What mass of CO₂ will be formed when 6g of carbon is burnt in 32 g of oxygen ?
(A) 38 g
(B) 12g
(C) 26 g
(D) 22 g
Answer. D

Question. The law of conservation of mass is valid for which of the following ? 
(a) Reactions involving oxidation (b) Nuclear reactions. (c) Endothermic reactions
(A) (a) and (c)
(B) (a) and (b)
(C) (b) and (c)
(D) (b) only
Answer. A

Question. Total number of atoms in 4 gm of oxygen molecule is : 
(A) 6.022×10²³
(B) 7.52×10²²
(C) 1.5055×10²³
(D) 0.0752×10²³
Answer. B

Question. In an organic compound of molar mass 108 g mol^–1 C, H and N atoms are present in 9 : 1 : 3.5 by weight.
Molecular formula can be : 
(A) C₆H₈N₂
(B) C₇H₁₀N
(C) C₅H₆N₃
(D) C₄H₁₈N₃
Answer. A

Question. 6.02 × 10²⁰ molecules of urea are present in 100 ml of its solution. The concentration of urea solution is -
(A) 0.001 M
(B) 0.01 M
(C) 0.02 M
(D) 0.1 M
Answer. B

Question. Two solution of a substance (non electrolyte) are mixed in the following manner. 480 ml of 1.5M first solution + 520 ml of 1.2M second solution. What is the molarity of the final mixture ? 
(A) 2.70M
(B) 1.344M
(C) 1.50M
(D) 1.20M
Answer. B

Question. How many moles of magnesium phosphate, Mg3(PO₄)₂ will contain 0.25 mole of oxygen atoms?
(A) 0.02
(B) 3.125 × 10^–2
(C) 1.25 × 10^–2
(D) 2.5 × 10^–2
Answer. B

Question. In the reaction 2AI_(s) + 6HCl_(aq) → 2Al³⁺ _(aq) + 6Cl^–_(aq)+ 3H₂ (g) 
(A) 6L HCl_(aq) is consumed for every 3L H2 produced.
(B) 33.6 L H_2(g) is produced regardless temperature and pressure for every moles that reacts.
(C) 67.2 L H_2(g) at STP is produced for every mole of Al that reacts .
(D) 11.2 L H_2(g) at STP is produced for every mole of HCl(aq) consumed.
Answer. D

Question. The density (in g mL^–1) of a 3.60 M sulphuric acid solution that is 29% (H₂SO₄ molar mass = 98 g mol^–1) by mass will be : 
(A) 1.22
(B) 1.45
(C) 1.64
(D) 1.88
Answer. A

Question. The density of a solution prepared by dissolving 120 g of urea (mol. mass = 60 u) in 1000 g of water is 1.15 g/mL. The molarity of this solution is : 
(A) 0.50 M
(B) 1.78 M
(C) 1.02 M
(D) 2.05 M
Answer. D

Question. The molarity of a solution obtained by mixing 750 mL of 0.5(M) HCl with 250 mL of 2(M)HCl will be :
(A) 0.875 M
(B) 1.00 M
(C) 1.75 M
(D) 0.975 M
Answer. A

Question. The hydrogen ion concentration in a mixture of 10 ml of 0.1 M H₂SO₄ and 10 ml of 0.1 M KOH solution in water, is 
(A) 0.1 M
(B) 0.05 M
(C) 0.2 M
(D) 0.02 M
Answer. B

Q1. Classify the following into elements, compounds and mixtures. Divide mixtures into homogeneous and heterogeneous (i) marble (ii) Honey (ii) Toothpaste (i) Sugar (v) gold (vi) Niter (vii) Iodized Table salt (viii) Iron (ix) Steel (x) Distilled water (xi) slaked lime (xii) oxygen (xiii) Gasoline (xiv) silk (xv) Tap water.

Q2. Classify following into metals and non-metals;- (i) Helium (ii) Sodium (iii) Mercury (iv) graphite (v) Carbon (vi) silicon (vii) Magnesium (viii) Phosphorous (ix) Arsenic (x) Antimony

Q3. How will you separate the constituents present in the following mixtures: - (i) common salt and water (ii) Iodine and sand (iii) sugar and sulphur (iv) Kerosene and water (v) salt + sand + sulphur + Iron

Q4. With the help of example justify each statement for different laws of chemical combination.

Q5 (i) How many gram molecules are present in 4.9g of H₂SO₄?
(ii) Calculate the mass of 0.72 molecules of CO_2.

Q6. Calculate the number of atoms in: - (i) 0.25 mole atoms of C (ii) 0.20 mole molecules of O₂.

Q7. How many atoms of carbon and oxygen are present in 1.5 mole of CO₂?

Q8. How many molecules and atoms of phosphorus are present in 0.1 moles of P4 molecules?

Q9. How many silver atoms are present in a piece of jewellery weighing 10.78 g? Ag = 107.8 a.m.u.

Q10. What weight of calcium contains the same number of atoms as per present in 3.2g of sulphur?

Q11. Calculate the number of atoms present in: - (i) 52 moles of He (ii) 52 a.m.u. of He (iii) 52g of He

Q12. Calculate the total number of electrons present in 1.6g of methane.

Q13. How many atoms of each type are present in 143g of washing soda (NaCO₃. 10 H₂O)?

Q14. Calculate the no. of moles of phosphorus in 92.9 g of ‘P’ assuming that molecular formula of ‘P’ is P4. Also calculate the no. of atoms and molecules of P in the sample.

Q15. What is the mass of 0.04 mol of Co₂?

Q16. Calculate the mass of water molecule?

Q17. How many molecules of water are there in 1L of water? The density of water is 1.0 g / ml.

Q18. How many moles of hydrogen are there in 0.925g of Ca (OH)₂ ? Ca = 40 a.m.u.

Q19. Calculate the mass of 1 molecule of CS₂?

Q20. 1 million atoms of silver weigh 1.79 x 10-16g. Calculate the atomic mass of silver.

Q21. Calculate the weight of CO moving same no. of oxygen atoms as are present in 88g of carbon dioxide?

Q22. Chlorophyll contains 2.68% of mg by weight. Calculate no. of mg atoms in 2.00 g of chlorophyll.(at mass of Mg = 24)

Q23. The cost of table salt and sugar are Rs. 2 per kg. and Rs. 6 per kg. respectively. Calculate the cost per mole.

Q24. Calculate the no. of gold atoms in 300 mg. Of a gold ring of 20 carat gold (at mass of gold = 197, pure gold is 24 carat).

Q25. Find the mass of an atom of silver. The molar mass of Ag atom is 108 g mol-.