ACSBR 7 Chemical Calculations - Assignment

Anglo-Chinese School (Barker Road) A Methodist Institution Founded in 1886 CHEMISTRY DEPARTMENT OF SCIENCE Name: ( ) Class: SEC 3 CHEMICAL CALCULATIONS – ASSIGNMENT ALEX LEE/2010 PAGE 1 OF 4 PURE/COMBINED Multiple-Choice Questions [20 Marks] TOTAL SCORE / 30 Write in your selected answer for the multiple-choice questions in the boxes provided. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 1. Which of the following statements about relative atomic mass is the least correct? A It is measured in grams. B It is compared to one-twelfth the mass of a carbon-12 atom. C It is the average number of protons and neutrons in an element. D It measures the average relative mass per atom. 2. The Avogadro constant is the number of A atoms in 6 g of graphite C molecules in 1 g of hydrogen gas B electrons in 10 g of neon D protons in 2 g of helium 3. If the number of similar particles in one mole is x, the number of chlorine molecules in 35.5 g of gaseous chlorine is A 0.5 x B x C 2 x D 35.5 x 4. The chloride of an unknown element E has a relative atomic mass of 136. Which of the following is most likely to be the formula for this chloride? A ECl B E2Cl C ECl2 D ECl3 5. What is the mass of one mole of anhydrous aluminium sulfate? A 123 grams B 170 grams C 278 grams D 342 grams 6. What is the relative molecular mass of copper(II) sulfate crystals, CuSO4.5H2O? A 160 B 178 C 234 D 250

ALEX LEE/2010 PAGE 2 OF 4 7. When two moles of magnesium metal becomes ions, A two moles of electrons are gained. C four moles of electrons are gained. B two moles of electrons are lost. D four moles of electrons are lost. 8. Which of the following contains 2 moles of atoms? A 12 g of carbon B 12 g of helium C 12 g of methane D 12 g of water 9. 0.2 mol of an unknown element M combines with 7.2 dm3 of chlorine (measured at r.t.p.) to form the compound MCln. What is the value of n? A 1 B 2 C 3 D 4 10. In 50 grams of calcium carbonate, there are x oxygen atoms present. What is x? A 0.5 mol B 1.5 mol C 2.5 mol D 3.0 mol 11. In 33 grams of (NH4)2SO4, there are y ions present. What is y? A 0.75 mol B 2.3 mol C 3.0 mol D 3.8 mol 12. When ethanol is combusted in excess oxygen, the following reaction takes place: C2H5OH (l) + 3 O2 (g) ⎯⎯→ 2 CO2 (g) + 3 H2O (g) What volume of water vapour is formed, at r.t.p., when 1.0 kilogram of ethanol is combusted? A 1000 24 3 46×× dm3 B 3 1000 24 46 × × dm3 C 46 24 3 1000×× dm3 D 3 46 24 1000 × × dm3 13. In the equation below, methane reacts with steam to form hydrogen and carbon monoxide: CH4 (g) + H2O (g) ⎯⎯→ CO (g) + 3 H2 (g) The volume of hydrogen that can be obtained from 100 cm3 of methane at r.t.p. is A 100 cm3. B 150 cm3. C 200 cm3. D 300 cm3. 14. What volume of oxygen gas, measured under room conditions, is needed to completely combust 3.60 grams of carbon into carbon dioxide? A 2,700 cm3 B 3,600 cm3 C 7,200 cm3 D 14,400 cm3 15. What volume of 0.120 mol dm-3 hydrochloric acid is need to completely react with 0.60 grams of magnesium metal? A 208 cm3 B 417 cm3 C 600 cm3 D 820 cm3

ALEX LEE/2010 PAGE 3 OF 4 16. What is the concentration of ions, in mol/dm3, in 39.2 g/dm3 sulfuric acid? A 0.400 B 1.20 C 1.64 D 13.0 17. What is the minimum volume of 0.100 mol dm-3 sodium hydroxide needed to completely neutralise 22.50 cm3 of 0.250 mol dm-3 sulfuric acid in the reaction below? 2 NaOH (aq) + H2SO4 (aq) ⎯⎯→ Na2SO4 (aq) + 2 H2O (l) A 1.13 cm3 B 9.00 cm3 C 45.0 cm3 D 113 cm3 18. In an industrial process, 42.5 g of ammonia was allowed to react with 72 dm3 of oxygen (measured at room conditions) to form nitrogen monoxide and water vapour. 4 NH3 (g) + 5 O2 (g) ⎯⎯→ 4 NO (g) + 6 H2O (g) Which is the limiting reagent in the above reaction? A NH3 B NO C O2 D H2O 19. Iron metal, when burnt in dry chlorine, forms iron(III) chloride. Suppose if 1.8 dm3 of chlorine is allowed to react with 1.4 grams of iron, what is the maximum mass of iron(III) chloride that can be formed? A 4.1 grams B 8.1 grams C 12.2 grams D 16.3 grams 20. If 36 dm3 of hydrogen were allowed to react with 32 grams of oxygen, what is the maximum mass of water that can be produced? A 27 grams B 32 grams C 36 grams D 72 grams Structured Questions [10 Marks] 21. A 4.00 g sample of copper(II) carbonate was allowed to react with 0.750 mol dm-3 nitric acid. (a) Construct a chemical equation, including state symbols, for the reaction. [1] (b) Find the number of moles of copper(II) carbonate present in the 4.00 g sample. [1]

ALEX LEE/2010 PAGE 4 OF 4 (c) Hence find the volume of nitric acid needed. [2] 22. When solutions of iron(II) nitrate and sodium hydroxide are mixed, a green precipitate of iron(II) hydroxide is formed. In an experiment, a student mixes a 5.0 cm3 sample of 0.250 mol dm-3 iron(II) nitrate with a 10 cm3 sample of 0.200 mol dm-3 sodium hydroxide. (a) Construct a chemical equation, including state symbols, for the reaction. [1] (b) By showing the relevant working, identify the limiting reagent. [3] (c) Hence calculate the mass of precipitate formed. [2] END