American International School of Johannesburg. Quantitative Revision Questions II

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1 American International School of Johannesburg Quantitative Revision Questions II 1. A toxic gas, A, consists of 53.8 % nitrogen and 46.2 % carbon by mass. At 273 K and Pa, g of A occupies 462 cm 3. Determine the empirical formula of A. Calculate the molar mass of the compound and determine its molecular structure. (Total 3 marks) mol of aluminium hydroxide is mixed with mol of sulfuric acid, and the following reaction occurs: 2Al(OH) 3 (s) + 3H 2 SO 4 (aq) Al 2 (SO 4 ) 3 (aq) + 6H 2 O(l) (a) Determine the limiting reactant (b) Calculate the mass of Al 2 (SO 4 ) 3 produced (c) Determine the amount (in mol) of excess reactant that remains (1) IB Questionbank Chemistry 1

2 3. Which sample of nitrogen gas, N 2, contains the greatest number of nitrogen molecules? A. 1.4 g N 2 B. 1.4 dm 3 of N 2 at Pa and 273 K C N 2 molecules D. 1.4 mol N 2 4. Which non-metal forms an oxide XO 2 with a relative molecular mass of 60? A. C B. N C. Si D. S 5. Aspirin, one of the most widely used drugs in the world, can be prepared according to the equation given below. (b) A student reacted some salicylic acid with excess ethanoic anhydride. Impure solid aspirin was obtained by filtering the reaction mixture. Pure aspirin was obtained by recrystallization. The following table shows the data recorded by the student. Mass of salicylic acid used Mass of pure aspirin obtained 3.15 ± 0.02 g 2.50 ± 0.02 g (i) Determine the amount, in mol, of salicylic acid, C 6 H 4 (OH)COOH, used. IB Questionbank Chemistry 2

3 (ii) Calculate the theoretical yield, in g, of aspirin, C 6 H 4 (OCOCH 3 )COOH. (iii) Determine the percentage yield of pure aspirin. (1) (iv) State the number of significant figures associated with the mass of pure aspirin obtained, and calculate the percentage uncertainty associated with this mass. (v) Another student repeated the experiment and obtained an experimental yield of 150 %. The teacher checked the calculations and found no errors. Comment on the result. (1) (Total 11 marks) IB Questionbank Chemistry 3

4 6. Smog is common in cities throughout the world. One component of smog is PAN (peroxyacylnitrate) which consists of 20.2 % C, 11.4 % N, 65.9 % O and 2.50 % H by mass. Determine the empirical formula of PAN, showing your working (Total 3 marks) 7. How many oxygen atoms are there in 0.20 mol of ethanoic acid, CH 3 COOH? A B C D mol of a hydrocarbon with an empirical formula of CH 2 has a mass of 280 g. What is the molecular formula of this compound? A. C 2 H 4 B. C 3 H 6 C. C 4 H 8 D. C 5 H 10 IB Questionbank Chemistry 4

5 9. Which coefficients would balance this equation? MnO 2 + HCl MnCl 2 + Cl 2 + H 2 O MnO 2 HCl MnCl 2 Cl 2 H 2 O A B C D What will be the concentration of sulfate ions in mol dm 3 when 0.20 mol of KAl(SO 4 ) 2 is dissolved in water to give 100 cm 3 of aqueous solution? A. 0.2 B. 1.0 C. 2.0 D What volume, in cm 3, of mol dm 3 HCl(aq) is required to neutralize 25.0 cm 3 of mol dm 3 Ba(OH) 2 (aq)? A B C D The volume of an ideal gas at 27.0 C is increased from 3.00 dm 3 to 6.00 dm 3. At what temperature, in C, will the gas have the original pressure? A B C. 327 D. 600 IB Questionbank Chemistry 5

6 13. The data below is from an experiment used to determine the percentage of iron present in a sample of iron ore. This sample was dissolved in acid and all of the iron was converted to Fe 2+. The resulting solution was titrated with a standard solution of potassium manganate(vii), KMnO 4. This procedure was carried out three times. In acidic solution, MnO 4 reacts with Fe 2+ ions to form Mn 2+ and Fe 3+ and the end point is indicated by a slight pink colour. titre initial burette reading / cm Final burette reading / cm Mass of iron ore / g concentration of KMnO 4 solution / mol dm (a) Deduce the balanced redox equation for this reaction in acidic solution (b) Identify the reducing agent in the reaction.... (1) (c) Calculate the amount, in moles, of MnO 4 used in the titration (d) Calculate the amount, in moles, of Fe present in the g sample of iron ore IB Questionbank Chemistry 6

7 (e) Determine the percentage by mass of Fe present in the g sample of iron ore (Total 9 marks) 14. Air bags in cars inflate when sodium azide decomposes to form sodium and nitrogen: 2NaN 3 (s) 2Na(s) + 3N 2 (g) Calculate the amount, in moles, of nitrogen gas produced by the decomposition of 2.52 mol of NaN 3 (s). A B C D What volume of carbon dioxide, in dm 3 under standard conditions, is formed when 7.00 g of ethene (C 2 H 4, M r = 28.1) undergoes complete combustion? A. B. C. D IB Questionbank Chemistry 7

8 16. What is the coefficient for H 2 SO 4 (aq) when the following equation is balanced, using the smallest possible integers? A. 1 B. 3 C. 4 Mg 3 N 2 (s) + H 2 SO 4 (aq) MgSO 4 (aq) + (NH 4 ) 2 SO 4 (aq) D How many hydrogen atoms are in one mole of ethanol, C 2 H 5 OH? A B C D IB Questionbank Chemistry 8

1. What is the sum of all coefficients when the following equation is balanced using the smallest possible whole numbers? D.

1. What is the sum of all coefficients when the following equation is balanced using the smallest possible whole numbers? A. 5 B. 7 C. 11 C 2 H 2 + O 2 CO 2 + H 2 O D. 13 2. 1.7 g of NaNO 3 (M r = 85)