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ICSE Notes 2018 : Chemistry (Respaper) ( Mole Concept Question Bank )

5 pages, 94 questions, 32 questions with responses, 38 total responses,

Ansh Singh
City Montessori School (CMS Aliganj Campus I), Lucknow

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SHORT ANSWER QUESTIONS 1. What is the value of the avogadro s number? 2. What is the value of molar volume of a gas at S.T.P? 3. What do you understand at S.T.P by the statement that vapour density of carbon dioxide is 22? 4. Define vapour density. State the relationship between vapour density and molecular weight. 5. Explain the following statement: Relative atomic mass of sodium is 23. LONG ANSWER QUESTIONS 1. State: a) Gay-Lussac s law of combining volumes b) Avogadro s law. 2. Define the terms: a) Vapour density b) Relative molecular weight , How are vapour density and molecular weight related? 3. Define a) Molar volume b) Avogadro s number. 4. A) Define relative atomic mass. B) Ordinary chlorine has two isotopes Cl -35 and Cl37 in the ratio of 3:1. Calculate the relative atomic mass of chlorine. 5. Explain the terms: a) Gram atom b) Gram mole. 6. A) What are the main applications of Avogadro s law? B) How does Avogadro s law explain Gay Lussac s law of combining volumes? 7. Explain the terms, empirical formula and molecular formula. 8. How is empirical formula related to molecular formula? If the molecular formula of the compound is C2H4O2, determine its empirical formula. NUMERICALS A. BASED ON GAY-LUSSAC S LAW 1. Ammonia may be oxidized to nitrogen monoxide in the presence of a catalyst according to the equation: 4NH3 + 5O2 ---> 4NO + 6H2O. If 27 litres of reactants are consumed, what volume of nitrogen monoxide is produced at the same temperature and pressure? 2. Water can split into hydrogen and oxygen under suitable conditions. If a given experiment results in 2500 cm3 of hydrogen being produced, what volume of oxygen is liberated under the same conditions of temperature and pressure? 3. What volume of propane is burnt for every 100 cm3 of oxygen used in the combustion reaction at s.t.p? 4. 450 cm3 of CO and 200 cm3 of oxygen are mixed together and ignited. Calculate the composition of the resulting mixture. 5. 200 ml of C2H4 is burnt in just sufficient air (complete combustion). Calculate the resulting mixture composition at 100oC and 760mm of Hg. B.BASED ON MOLE CONCEPT AVOGADRO S NUMBER 1. Calculate the mass of 0.2 moles of water. 2. How many moles of sodium hydroxide are contained in 160g of it? 3. Calculate the weight of 6.023 X 1023 molecules of NaCl. 4. What will be the number of atoms in 1 mole of N2? 5. Calculate the number of molecules in 11.2 litres of CO2 gas at S.T.P. 6. A piece of silver metal weighs 10.8g. How many atoms of Ag does it contain? 7. Calculate (a) weight in grams (b) number of moles (c) number of molecules in 44.8 dm3 of carbon dioxide at S.T.P. 8. Calculate the number of grams of oxygen in 0.1 mole of Na2CO3.10H2O. 9. A certain sample of nitrogen gas consists of 9.26 X 1022 nitrogen atoms. a. How many moles of nitrogen atoms are present in this sample? b. If the gas is entirely in molecular form, how many moles of N2 molecules are present in this sample? c. What is the mass of the sample? 10. Calculate the number of oxygen atoms and its weight in 50g of CaCO3. C. BASED ON AVOGADRO S LAW 1. Under same conditions of temperature and pressure, you collect, 2 litres of CO2, 3 litres of Cl2, 5 litres of H2, 4 litres of N2 and 1 litre of SO2. In which gas sample will there be: a. the greatest number of molecules? b. the least number of molecules? 2. a) A vessel contains N molecules of oxygen at certain temperature and pressure. How many molecules of SO2 can the vessel accommodate at the same temperature and pressure? (b) Each of two flasks contains 2.0g of gas at the same temperature and pressure. One flask contains oxygen and the other hydrogen. i. Which sample contains greater number of molecules? ii. If the hydrogen sample contains N molecules, how many molecules are present in oxygen sample? 3. A gas cylinder can hold 1Kg of hydrogen at room temperature and pressure. i. What mass of CO2 can it hold under similar conditions of temperature and pressure? Ii. If the number of molecules of hydrogen in the cylinder. Give reasons for your answer. 4. The following gases collected under the same conditions of temperature and pressure occupy the volume as given below: Chlorine = 10 litres; Nitrogen = 20 litres ; NH3 = 15 litres; CO2 = 5 litres. If nitrogen contains x molecules, find the number of molecules in chlorine, ammonia and carbon dioxide. D.BASED ON VAPOUR DENSITY AND MOLECULAR WEIGHT 1. Atomic weight of chlorine is 35.5. What is its vapour density? 2. 2.8 dm3 of a gas X at S.T.P is found to weigh 5.5g. Calculate (a) Molecular mass (b) V.P of gas. 3.A gas cylinder filled with hydrogen holds 5g of a gas. The same cylinder holds 85g of a gas X under same temperature and pressure. Calculate the vapour desity and molecular weight of the gas X. 4. A gas cylinder can hold 5.6g of hydrogen at S.T.P. a. Calculate the amount of sulphur dioxide gas it can hold at S.T.P. b. If the number of molecules of hydrogen is X, Calculate the number of molecules of SO2 present in it. 5. 3g of a gas occupies a volume of 700ml at a temperature of 70oC and 700 mm of pressure. Give that 1 litre of hydrogen weighs 0.09g at S.T.P., find the vapour density and molecular weight of the gas. E. BASED ON PERCENTAGE COMPOSITION 1. Calculate the percentage of nitrogen in ammonium nitrate. 2. Calculate the percentage of water of crystallization in washing soda. 3. Calculate the percentage of pure iron in 10 kg of Fe2O3 of 80% purity. 4. Urea [NH2 CONH2] and ammonium sulphate [(NH4)2 SO4] are fertilizers? Which of the above fertilisers is a better fertilizer? [At. Wt. of N=14, H=1, C=12, O=16, S=32] 5. Copper sulphate crystals (CuSO4.5H2O) lose the whole of their water of crystallization heating. Calculate the percentage loss in weight that will take place on heating a sample of crystals.[At. Wt. of Cu=63.5, S=32, O=16, H=1] 6. Percentage of water of crystallization in BaCl2.xH2O was found to be 14.73%. Find the number of molecules of water of crystallization, x in the compound. 7. Calculate the number of water of crystallization in hydrated copper sulphate crystals, if 10gm of hydrous copper sulphate crystals gives 6.4g anhydrous CuSO4 on heating.[ Cu = 64] 8. Calculate the total percentage of oxygen in magnesium nitrate crystals, Mg(NO3)2.6H2O. 9. What is the mass of nitrogen in 1000 kg of urea [CO(NH2)2]? 10. Calculate the percentage of boron in Borax Na2B4O7.10H2O F. BASED ON EMPIRICAL AND MOLECULAR FORMULAE 1. A compound of Na, S and O has the following percentage composition: Na = 29.11%, O = 30.38% and S = 40.51%. Find its empirical formula. 2. Find the empirical formula and empirical formula of an acid of phosphorus which has the following composition: 2.47% of H, 38.27% of P and 59.26% of oxygen. The relative molecular mass is 162. 3. A compound contains 87.5% by mass of nitrogen and 12.5% by mass of hydrogen. Determine the empirical formula of the compound. 4. The empirical formula of a compound is C2H5. Its vapour density is 29. Determine the relative molecular mass of the compound and hence, its molecular formula. 5. The compound A has the percentage composition by following mass: Carbon 26.7%, Oxygen 71.1% and Hydrogen 2.2%. Determine the empirical and molecular formula of A, if its molecular weight is 90. G. BASED ON CHEMICAL EQUATIONS 1. Aluminum carbide react with water according to the following equation: Al4C3 + 12H2O 3CH4 + 4Al(OH)3. Calculate the volume of methane measured at S.T.P released from 14.4g of aluminum carbide by excess of water. 2. (a) Iron pyrites has the formula FeS2, what mass of sulphur is contained in 30g of pyrites? (b) When roasted, iron pyrites give sulphur dioxide according to the following equation: 4FeS2 + 11O2 ---> 2Fe2O3 + 8SO2. What volume of SO2 would be liberated by roasting 30g of pyrites? [Fe = 56] 3. a) What volume of hydrogen sulphide at S.T.P will burn in oxygen to yield 12.8g sulphur dioxide according to the equation: 2H2S + 3O2 ----> 2H2O + 2SO2? (b) For the volume of hydrogen sulphide determined in (i) above, what volume of oxygen would be required for complete combustion? 4. Concentrated nitric acid oxidizes phosphorus to phosphoric acid according to the following equation: P + 5HNO3 ----> H3PO4 + H2O + 5NO2 a. What mass of Phosphoric acid can be prepared from 6.2g of phosphorus? b. What mass of nitric acid will be consumed at the same time? c. What would be the volume of steam produced at the same time if measured at 760mm and 273oC? 5. If a crop of wheat removes 20 kg of nitrogen per hectare of soil, what mass of the fertilizer calcium nitrate would be required to replace the nitrogen in a 10 hectare field? 6. Calcium hydroxide reacts with ammonium chloride to give ammonia, according to the following equation: Ca(OH)2 + 2NH4Cl --> CaCl2 + 2NH3 + 2H2O . If 5.35g of ammonium chloride are used, calculate: a. The mass of Calcium chloride formed and b. The volume, at S.T.P of NH3 liberated. 7. Calcium nitrate decomposes on heating according to the following equation: 2Ca(NO3)2 ---> 2CaO + 4NO2 +O2 The relative molecular mass of calcium nitrate is 164.. Calculate (a) The volume of nitrogen dioxide (NO2) obtained at S.T.P and (b) The mass of calcium oxide obtained when 16.4 g of calcium nitrate is heated at constant mass. 8. Ammonia burns in oxygen. The combustion in the presence of a catalyst may be represented by: 4 NH3 + 5O2 --> 2NIO + 3H2O what mass of steam is produced when 1.5 g of nitrogen monoxide is formed 9. The equation for the reaction between carbon and sulphuric acid is given below: C + 2H2SO4 CO2 + 2H2O + 2SO2 Calculate: a. The mass of carbon oxidized by 49g of sulphuric acid. b. The volume of gases measured at S.T.P evolved at the same time. CONCEPTUAL QUESTIONS 1. A sample of coal gas contained 45% H2, 30% CH4, 20% CO and 5% C2H2 by volume. 100ml of this gaseous mixture was mixed with 160 ml of oxygen and exploded. Calculate the volume and the composition of the resulting mixture, when cooled to room temperature and pressure. 2. A compound has O = 61.32%, S = 11.15%, H = 4.88% and Zn = 22.65%. The relative molecular mass of the compound is 287 amu. Find the molecular mass of the compound, assuming that all the hydrogen is present as water of crystallization. [ Zn = 65] 3. A 2.00 g sample containing Na2CO3 and NaHCO3 loses 0.248 g when heated to 300oC, the temperature at which NaHCO3 decomposes to Na2CO3, CO2 and water. 4. 1.84g of a mixture of CaCO3 and MgCO3 are heated strongly till no further loss of weight takes place. The residue weighs 0.96g. Find the percentage composition of the mixture. 5. 24ml of methane were mixes with 106 ml of oxygen and the mixture was exploded. The product, after cooling, measured 82ml, of which 58 ml were unused oxygen. Show that these results illustrate Gay-Lussac s law.

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