Moles.docx

O LEVEL PAST PAER QUESTIONS.__________________________________________________________________________________________TOPIC 4: Moles

PART-1 MCQs1- A 25 cm3 sample of dilute sulphuric acid contains 0.025 moles of the acid.What is the hydrogen ion concentration in the solution?A 0.25 mol / dm3B 0.50 mol / dm3C 1.00 mol / dm3D 2.00 mol / dm3 [JUNE 2003]2- Which sulphide contains the greatest mass of sulphur in a 10 g sample? [JUNE 2003]3- 124 g of phosphorus vapour has the same volume as 71 g of chlorine gas at thesame temperature and pressure.What is the formula of a molecule of phosphorus?A P 8 B P4 C P2 D P [JUNE 2003]4- What is the mass of magnesium which completely reacts with 250 cm3 of 1.0 mol/dm3 sulphuricacid?A 6 g B 12 g C 48 g D 96 g5- A volume of ethane, C2H6, at r.t.p. has a mass of 20 g.What is the mass of an equal volume of propene, C3H6, at r.t.p.?A 20 g B 21 g C 28 g D 42 g [NOV-2003]6- 'Cracking' of hydrocarbons breaks them into smaller molecules.Which example of 'cracking' would produce the largest volume of products from one mole ofhydrocarbon? Assume that all measurements are made at the same temperature and pressure.

7- When 20 cm3 of a gaseous alkene burns in an excess of oxygen, 60 cm3 of carbon dioxide areformed. Both volumes are measured at r.t.p.

What is the formula of the alkene?A C3H6B C3H8C C6H12D C6H14 [NOV-2004]8- All ammonium salts on heating with sodium hydroxide produce ammonia gas.From which ammonium salt can the greatest mass of ammonia be obtained?A 0.5 mol (NH4)3PO4B 0.5 mol (NH4)2SO4C 1.0 mol NH4ClD 1.0 mol NH4NO3 [NOV-2004]9- How many moles per dm3 of gaseous carbon dioxide are there if 4.4 g occupies 500 cm3?A 0.1 mol /dm3 B 0.2 mol /dm3 C 2.2 mol /dm3 D 8.8 mol /dm3 [JUNE- 2005]10- Element X is a solid at room temperature.It needs one electron per atom to gain the electronic structure of a noble gas.It is the least reactive element in its group.What is the element X?A At B Cs C F D Li [JUNE- 2005]11- Aluminium sulphate can be obtained as shown in the equation. How many moles of sulphuric acid are needed to produce 0.5 mol of aluminium sulphate?A 0.5 B 1.0 C 1.5 D 3.0 [JUNE- 2005]12- The diagram shows the electrolysis of a concentrated aqueous solution containing bothcopper(II) ions and sodium ions. Which metal is deposited at the negative electrode and why?

13- Which pollutant increases the growth of algae in rivers and streams?A chlorineB heavy metal ionsC nitrate ionsD sulphur dioxide14- What is the mass of aluminium in 204 g of aluminium oxide, Al2O3?A 26 g B 27 g C 54 g D 108 g15- 2 dm3 of aqueous sodium hydroxide of concentration 5 mol /dm3 were required for an experiment.How many moles of sodium hydroxide were needed to make up this solution?A 2.5 B 5 C 7 D 1016- An 8 g sample of oxygen atoms contains the same number of atoms as 16 g of element X.What is the relative atomic mass, Ar, of X?A 4 B 8 C 16 D 3217- Which quantity is the same for one mole of ethanol and one mole of ethane?A massB number of atomsC number of moleculesD volume at r.t.p.18- In an experiment 264 g of strontium reacts with 213 g of chlorine.What is the formula of strontium chloride?A SrCl B SrCl2 C SrCl3 D Sr2Cl19- The element X forms a gaseous molecule X2. One volume of X2 combines with one volume ofhydrogen to form two volumes of a gaseous hydride.What is the formula for the hydride of X?A HX B HX2 C H2X D H2X220- Which substance has the highest percentage by mass of nitrogen?A NH4NO3 Mr = 80B (NH4)2SO4 Mr = 132C CO(NH2)2 Mr = 60D (NH4)3PO4 Mr = 14921- The equation represents the action of dilute nitric acid on copper.xCu + yHNO3 xCu(NO3)2 + 4H2O + 2NOWhat are the values of x and y?A x = 1, y = 4B x = 1, y = 8C x = 3, y = 4D x = 3, y = 822- Which statement about the substance formed when a given mass of an element burns in excessoxygen is always correct?The substance formed isA denser than the element.B greater in mass than the element.C soluble in water.D white in colour.23- The diagram shows apparatus for measuring the volume of hydrogen given off when an excess ofdilute hydrochloric acid is added to powdered metal. The volume of gas is measured at roomtemperature and pressure.

The experiment is carried out three times, using the same mass of powder each time but withdifferent powders: pure magnesium pure zinc a mixture of magnesium and zincWhich powder gives the greatest volume of hydrogen and which the least volume?

24- All ammonium salts on heating with sodium hydroxide produce ammonia gas.From which ammonium salt can the greatest mass of ammonia be obtained?A 0.5 mol (NH4)3PO4B 0.5 mol (NH4)2SO4C 1.0 mol NH4ClD 1.0 mol NH4NO325- In which oxide does X have the same oxidation state as in the chloride, XCl3?A X3O B X2O C XO2 D X2O326- One mole of a sample of hydrated sodium sulphide contains 162 g of water of crystallisation.What is the correct formula of this compound?A Na2S.3H2O B Na2S.5H2O C Na2S.7H2O D Na2S.9H2O27- Carbon dioxide can be obtained as shown in the equation. 3Na2CO3 + 2H3PO4 2Na3PO4 + 3CO2 + 3H2OHow many moles of phosphoric acid, H3PO4, are needed to produce 1.5 mol of carbon dioxide?A 0.5 B 1.0 C 1.5 D 2.028- The fertiliser ammonium nitrate (NH4NO3, Mr = 80) is manufactured from ammonia (NH3, Mr = 17)by a two-stage process. Stage 1 NH3 + 2O2 HNO3 + H2O Stage 2 HNO3 + NH3 NH4NO3What is the maximum mass of fertiliser that can be made if only 17 tonnes of ammonia is available?A 34 tonnes B 40 tonnes C 80 tonnes D 97 tonnes29- Which gas contains the same number of molecules as 9 g of water?A 2 g of hydrogenB 14 g of nitrogenC 32 g of oxygenD 44 g of carbon dioxide30- The equation for the reaction between copper and nitric acid is shown. vCu + wHNO3 xCu(NO3)2 + yNO + zH2Ov, w, x, y and z are whole numbers.Which values of v, w, x, y and z balance the equation?

31- Which reactions take place during the electrolysis of aqueous copper(II) sulfate with copper electrodes?

32- The relative atomic mass of oxygen is 16.What are possible values of the relative molecular mass of different molecules of water formed bythe combination of oxygen and hydrogen?1 182 193 20A 1 onlyB 1 and 2 onlyC 1 and 3 onlyD 1, 2 and 333- Calcium reacts with water as shown. Ca(s) + 2H2O(l) Ca(OH)2(aq) + H2(g)What is the total mass of the solution that remains when 40 g of calcium reacts with 100 g ofwater?A 58 g B 74 g C 138 g D 140 g34- Hydrogen reacts with oxygen as shown in the equation below. 2H2(g) + O2(g) 2H2O(l)How much gas will remain if 2 dm3 of hydrogen are reacted with 1 dm3 of oxygen at roomtemperature?A 0 dm3 B 1 dm3 C 2 dm3 D 3 dm335- Two different hydrocarbons each contain the same percentage by mass of hydrogen.It follows that they have the sameA empirical formula.B number of isomers.C relative molecular mass.D structural formula.36- What is the mass of one mole of carbon-12?A 0.012 g B 0.024 g C 1 g D 12 g37- What is the concentration of iodine molecules, I2, in a solution containing 2.54 g of iodine in250 cm3 of solution?A 0.01 mol /dm3B 0.02 mol /dm3C 0.04 mol /dm3D 0.08 mol /dm338- What is the mass of oxygen contained in 72 g of pure water?[Relative atomic masses: H = 1; O = 16]A 16 g B 32 g C 64 g D 70 g39- The equation for the reaction between calcium carbonate and hydrochloric acid is shown. CaCO3(s) + 2HCl(aq) CaCl2(aq) + H2O(l) + CO2(g)How many moles of calcium carbonate will give 24 cm3 of carbon dioxide when reacted with anexcess of the acid?(Assume one mole of carbon dioxide occupies 24 dm3.)A 1 mol B 0.1 mol C 0.01 mol D 0.001 mol40- The empirical formula of a liquid compound is C2H4O.To find the empirical formula, it is necessary to know theA density of the compound.B percentage composition of the compound.C relative molecular mass of the compound.D volume occupied by 1 mole of the compound41- What is the relative molecular mass Mr of CuSO4.5H2O?A 160 B 178 C 186 D 25042- What is the ratio of the number of molecules in 71 g of gaseous chlorine to the number ofmolecules in 2 g of gaseous hydrogen? [Relative atomic masses Ar (atomic weights): H, 1: Cl,35.5]A 1 : 1 B 1 : 2 C 2 : 1 D 71 : 243- Which equation shows a reaction that would actually take place?A 2MgO + C CO2 + MgB MgO + Cu CuO + MgC PbO + Zn ZnO + PbD ZnO + H2 H2O + Zn44- What has the same mass as 0.25 mol of copper atoms?A 0.5 mol of oxygen moleculesB 1 mol of sulfur dioxide moleculesC 1.5 mol of water moleculesD 2 mol of oxygen atoms45- A 10 cm3 sample of a gaseous hydrocarbon is completely burnt in oxygen. The total volume of theproducts is 70 cm3. All gas volumes are measured at room temperature and pressure.Which equation represents the combustion of the hydrocarbon?A CH4(g) + 2O2(g) CO2(g) + 2H2O(g)B C2H4(g) + 3O2(g) 2CO2(g) + 2H2O(g)C C3H8(g) + 5O2(g) 3CO2(g) + 4H2O(g)D 2C2H6(g) + 7O2(g) 4CO2(g) + 6H2O(g)46- 0.5 mol /dm3 hydrochloric acid is added gradually to a flask containing 20 cm3 of 2 mol /dm3sodium hydroxide solution.What is the total volume, in cm3, of the mixture in the flask when the solution is just neutral?A 30 B 40 C 60 D 10047- Two of the reactions used in the manufacture of nitric acid, HNO3, are shown.2NO + O2 2NO24NO2 + 2H2O + O2 4HNO3What is the maximum number of moles of nitric acid which could be formed from one mole ofnitrogen monoxide, NO?A 0.5 B 1.0 C 2.0 D 4.048- One volume of a gaseous element X2 combines with an equal volume of gaseous hydrogen toform two volumes of a gaseous hydride.What is the formula for the hydride of X?A H2X B HX C HX2 D H2X249- The relative atomic mass of chlorine is 35.5.What is the mass of 2 moles of chlorine gas?A 17.75 g B 35.5 g C 71 g D 142 g50- The compounds CO(NH2)2 and NH4NO3 are used as fertilisers.The proportion of nitrogen by mass in CO(NH2)2 is 1 that in NH4NO3.The proportion of nitrogen by mole in CO(NH2)2 is 2 that in NH4NO3.Which words correctly complete gaps 1 and 2?

51- 18 g of water contains the same number of molecules asA 18 g of ammonia gas.B 2 g of hydrogen gas.C 14 g of nitrogen gas.D 16 g of oxygen gas.52- The complete combustion of 20 cm3 of a gaseous alkane, X, requires 130 cm3 of oxygen. Bothvolumes were measured at r.t.p..What could be the identity of X?A butaneB ethaneC methaneD propane53- Sodium hydrogencarbonate decomposes on heating. 2NaHCO3 Na2CO3 + H2O + CO2In an experiment, a 5.0 mol sample of sodium hydrogencarbonate is heated.Which volume of carbon dioxide, measured at room temperature and pressure, is evolved?A 24 dm3 B 36 dm3 C 48 dm3 D 60 dm354- What is the percentage, by mass, of nitrogen in the fertiliser (NH4)3PO4?[Ar: H, 1; N, 14; O, 16; P, 31]A 9.4% B 18.8% C 28.2% D 37.6%

PAPER -2 THEORY1- Marble statues are being damaged by acid rain. The chemical name for marble is calciumcarbonate.A student investigated the reaction between marble chips and nitric acid.

CaCO3(s) + 2HNO3 (aq) Ca(NO3)2(aq) + H2O(l) + CO2(g)The diagram shows the apparatus the student used.

The student recorded the balance reading every minute.The table shows the results.5070/02/M/J/03(a) Explain why the balance reading decreases during the experiment.................................................................................................................................................................................................................................................................................[1](b) How can the student tell when the reaction has finished?................................................................................................................................................................................................................................................................................[1]7(c) (i) Calculate the number of moles of nitric acid in 50 cm3 of 2.0 mol / dm3 solution.

(ii) Calculate the number of moles of calcium carbonate in 2.0 g.

(iii) Which reagent, calcium carbonate or nitric acid, is in excess?Explain your answer.

[5](d) The student repeats the experiment using the same quantities of calcium carbonate andnitric acid. This time the acid is at a higher temperature. Describe and explain, in termsof collisions between reacting particles, the effect of increasing the temperature on therate of reaction...........................................................................................................................................................................................................................................................................................................................................................................................................................[2] [JUNE-2003]2-

(b) Potassium reacts with water as shown in the equation.2K(s) + 2H2O(l) 2K+(aq) + 2OH(aq) + H2(g)Describe what you would see when potassium reacts with water...........................................................................................................................................................................................................................................................................................................................................................................................................................[2](c) A sample of 0.195 g of potassium was added to 500 cm3 of cold water. When thereaction was finished, 100 cm3 of 0.100 mol/dm3 hydrochloric acid was added to formsolution X.(i) Calculate the number of moles of hydroxide ions formed when the potassium wasadded to water.

(ii) Calculate the number of moles of hydrogen ions in 100 cm3 of 0.100 mol/dm3hydrochloric acid.

(iii) Give an ionic equation to represent the neutralisation reaction....................................................................................................................................(iv) Suggest a pH value for solution X.Explain your answer.................................................................................................................................................................................................................................................................................................... [4]Draw the electronic structure of both a potassium ion and an oxide ion.Include the charge on each ion.Potassium ion

Oxide ion

[2]2- A fertiliser contains three compounds: ammonium sulphate, (NH4)2SO4, iron(II) sulphate, FeSO4, sand, SiO2.(a) Calculate the percentage by mass of nitrogen in ammonium sulphate.

.................................. % [2]

(b) Aqueous iron(II) ions and aqueous iron(III) ions can be distinguished by reaction withaqueous sodium hydroxide. Describe what you would observe as a result of eachreaction.observation with aqueous iron(II) ions ......................................................................................................................................................................................................................observation with aqueous iron(III) ions .................................................................................................................................................................................................................[2](c) Aqueous iron(II) ions can be oxidised by reaction with acidified potassiummanganate(VII), KMnO4. The colour change during the reaction shows that iron(II) ionsact as a reducing agent.(i) Describe the colour change during the reaction............................................................................................................................... [1](ii) In terms of oxidation numbers, explain the meaning of the term reducing agent................................................................................................................................................................................................................................................................. [1](d) The mass of iron(II) ions in a sample of fertiliser can be determined by the reactionbetween iron(II) ions and acidified potassium manganate(VII), KMnO4.A student analysed a sample of the fertiliser. He dissolved the sample in 25.0 cm3 ofdilute sulphuric acid and titrated the solution formed with 0.0200 mol / dm3 potassiummanganate(VII).The student used 22.5 cm3 of potassium manganate(VII) to reach the end-point.(i) Calculate the number of moles of potassium manganate(VII) used in the titration.

................................ moles [1](ii) One mole of potassium manganate(VII) reacts with five moles of iron(II) ions.Calculate the mass, in grams, of iron(II) ions in the sample analysed.

................................ g [2] [Total: 9] [JUNE 2007]3-