ACSBR 7 Chemical Calculations - Assignment ANS

Anglo-Chinese School (Barker Road) A Methodist Institution Founded in 1886 CHEMISTRY DEPARTMENT OF SCIENCE Name: ANSWERS ( ) 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 A D A C D D D D C B 11 12 13 14 15 16 17 18 19 20 A C D C B B D C A A 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. Wh