HOME WORK - 31/10/2019 - CHEMISTRY - NIOS - 313
Senior Secondary Course

Module I Some Basic Concepts of Chemistry - HW-01-01

Chapter Name - Atoms, Molecules and Chemical Arithmetic - 1
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Q1. Chemistry plays a vital role in many areas of science and technology. What are those areas?

Q2. Who proposed the particulate nature of matter?

Q3. What is law of conservation of mass?

Q4. What is an atom?

Q5. What is a molecule?

Q6. Why is the symbol of sodium Na?

Q7. How is an element different from a compound?

Q8. A sample of nitrogen gas consists of 4.22 × 1023 molecules of nitrogen. How many moles of nitrogen gas are there?

Q9. In a metallic piece of magnesium, 8.46 × 1024 atoms are present. Calculate the amount of magnesium in moles.

Q10. Calculate the number of Cl2 molecules and Cl atoms in 0.25 mol of Cl2 gas. Calculate the molar mass of
     (i) K2SO4 (ii) Ba3(PO4)2. 

Q11.Find out the mass of carbon -12 that would contain 1.0 × 10*19 carbon-12 atoms. Molar mass of O is 16 g mol–1. What is the mass of one atom and
    one molecule of oxygen?

Q12. Calculate the molar mass of hydrogen chloride, HCl.

Q13. Calculate the molar mass of argon atoms, given that the mass of single atom is 6.634 × 10–26 kg.

Q14. Molar mass of O is 16 g mol–1. What is the mass of one atom and one molecule of oxygen?

Q15. Calculate the mass of 1.0 mol of potassium nitrate, KNO3 (atomic masses :K = 39 amu; N = 14 amu, O = 16 amu).

Q16. The formula of sodium phosphate is Na3PO4. What is the mass of 0.146 mol of Na3PO4? (atomic masses : Na = 23.0 amu, P = 31.0 amu; O = 16.0amu).

Q17. In a reaction, 0.5 mol of aluminium is required. Calculate the amount of aluminium required in grams? (atomic mass of Al = 27 amu)

Q18. How many moles of Cu atoms are present in 3.05 g of copper (Relative atomic mass of Cu = 63.5).

Q19. A piece of gold has a mass of 12.6 g. How many moles of gold are present in it? (Relative atomic mass of Au = 197)

Q20. In a combustion reaction of an organic compound, 2.5 mol of CO2 were produced. What volume would it occupy at STP (273K, 1bar) ?

Q21. For the compound Fe3O4, calculate percentage of Fe and O.

Q22. State percent composition for each of the following:(a) C in SrCO3 (b) SO3 in H2SO4

Q23. What are the empirical formulae of substances having the following molecular formulae? H2O2, C6H12, Li2CO3, C2H4O2, S8, H2O, B2H6, O3, S3O9, N2O3

Q24. A compound is composed of atoms of only two elements, carbon and oxygen. If the compound contain 53.1% carbon, what is its empirical formula

Q25. In the manufacture of ammonia by Haber process, nitrogen reacts with hydrogen at high temprature and high pressure in the presence of a catalyst
and gives ammonia.N2(g) + 3H2(g) --> 2NH3(g).How much hydrogen would be needed to produce one metric ton of ammonia?

Q26. When lead sulphide; PbS and lead oxide, PbO, are heated together the products are lead metal and sulphur dioxide, SO2, PbS(s) + 2PbO(s) --> heat --> 3Pb (1) + SO2(g)

Q27. 2.3 g of sodium metal is introduced into a 2L flask filled with chlorine gas at STP (273 K, 1bar). After the reaction is over, find :
(i) What is the limiting reagent in this reaction?
(ii) How many moles of sodium chloride are formed?
(iii) Which substance is left unconsumed at the end of the reaction? Find out its mass in grams.
(iv) What percentage of the substance present in excess is converted into sodium chloride? (Given : Na = 23, Cl = 35.5)

Q28. 2.0 g mixture of MgCO3 and CaCO3 are heated till no further loss of weight takes place. The residue weighs 1.04 g. Find the percentage composition of the mixture. (Mg = 24, Ca = 40, C = 12, O = 16)

Q29. How many atoms are present in a piece of iron that has a mass of 65.0 g/(atomic mass; Fe = 55.9 amu).

Q30. A piece of phosphorus has a mass of 99.2 g. How many moles of phosphorus,P4 are present in it? (atomic mass, P = 31.0 amu)

Q31. Mass of 8.46 × 1024 atoms of fluorine is 266.95 g. Calculate the atomic mass of fluorine.

Q32. A sample of magnesium consists of 1.92 × 1022 Mg atoms. What is the mass of the sample in grams? (atomic mass = 24.3 amu)

Q33. Calculate the molar mass in g mol–1 for each of the following:
(i) Sodium hydroxide, NaOH
(ii) Copper Sulphate CuSO4 .5H2O.
(iii) Sodium Carbonate, Na2CO3 .10H2O

Q34. For 150 gram sample of phosphorus trichloride ( PCl3 ), calculate each of the following:
(i) Mass of one PCl3 molecule.
(ii) The number of moles of PCl3 and Cl in the sample.
(iii)The number of grams of Cl atoms in the sample.
(iv)The number of molecules of PCl3 in the sample.

Q35. Find out the mass of carbon-12, that would contain 1 × 1019 atoms.

Q39. How many atoms are present in 100 g sample of C-12 atom?

Q40. How many moles of CaCO3 would weigh 5 g?

Q41. If you require 1.0 × 1023 molecules of nitrogen for the reaction N2 + 3H2 → 2NH3.
(i) What is the mass (in grams) of N2 required?
(ii) How many moles of NH3 would be formed in the above reaction from 1.0 × 1023 molecules of N2?
(iii) What volume would NH3 gas formed in (ii) occupy at STP?

Q42. Write empirical formulae of the following compounds:CO, Na2SO3, C4H10, H2O2, KC1

Q43. The empirical formula of glucose is CH2O which has a formula mass of 30amu. If the molecular mass of glucose is 180 amu. Determine the molecular formula of glucose

Q44. What is ratio of masses of oxygen that are combined with 1.0 gram of nitrogen in the compound NO and N2O3?

Q46. A compound containing sulphur and oxygen on analysis reveals that it contains 50.1% sulphur and 49.9% oxygen by mass. What is the simplest formula of the compound?

Q47. Hydrocarbons are organic compound composed of hydrogen and carbon.A, 0.1647 g sample of a pure hydrocarbon on burning in a combustion tube produced 0.5694 g of CO2and 0.0845 g of H2O. Determine the percentage of these elements in the hydrocarbon.

Q48. (i) What mass of oxygen is required to react completely with 24 g of CH4 in the following reaction? CH4(g) + 2O2(g) → CO2(g) + 2H2O(1) (ii) How much mass of CH4would react with 96 g of oxygen.

Q49. In the reaction H2+ C12 → 2HC1 How many grams of chlorine, C12 are needed to react completely with 0.245 g of hydrogen, H2, to give hydrogen chloride, HC1? How much HC1 is formed?. 

Q50. 3.65 g of H2 and 26.7 g of O2 are mixed and reacted. How many grams of H2O are formed?. 

Q51. Caustic soda NaOH can be commercially prepared by the reaction of Na2CO3 with slaked line, Ca(OH)2. How many grams of NaOH can be obtained by treating 2.0 kg of Na2CO3 with Ca(OH)2 ?

Q52. A portable hydrogen generator utilizes the reaction CaH2 + H2O → Ca(OH)2 + 2H2 How many grams of H2 can be produced by a 100 g cartridge of CaH2?

Q53. 2.0 g of a mixture of Na2CO3 and NaHCO3 was heated when its weight reduced to 1.876 g. Determine the percentage composition of the mixture.

Q54. Calculate the weight of 60 % sulphuric acid required to decompose 150 g of chalk (calcium carbonate). Given Ca = 40, C = 12, O = 16, S = 32).

Q55. The reaction 2Al + 3MnO → Al2O3+ 3Mn proceeds till the limiting substance is consumed. A mixture of 220 g Al and 400 g MnO was heated to initiate the reaction. Which initial substance remained in excess and by how much ? ( Al = 27, Mn = 55).

Q56. On combustion 2.4 g of a compound of carbon, hydrogen and oxygen gave3.52 g of CO2and 1.44 g of H2O. The molecular mass of the compound was found to be 60.0 amu.(a) What are the masses of carbon, hydrogen and oxygen in 2.4 g of the compound?(b) What are the empirical and molecular formulae of the compound?