WJEC Chemistry for AS Level Student Book: 2nd Edition (Draft)

WJEC Chemistry for AS Level

6. Titanium can be manufactured by the Kroll process as shown by the following equations: TiO 2 + 2Cl 2 + C → TiCl 4 + CO 2 (1) TiCl 4 + 2Mg → Ti + 2MgCl 2 (2) (a) Calculate the atom economy for the production of titanium in equation (2). [2] (b) Calculate the maximum mass of titanium which could be obtained from 447 kg of titanium(IV) oxide. [2] 7. Glauber’s salt is a form of hydrated sodium sulfate. It can be represented by the formula Na 2 SO 4 . x H 2 O. When 5.42 g of this hydrate was heated, 2.39 g of the anhydrous salt, Na 2 SO 4 , remained. Calculate the value of x in Na 2 SO 4 . x H 2 O [3] 8. Edmund was asked to find the identity of a group 1 metal carbonate. He fully dissolved 0.723 g of the carbonate in water to form a solution. The solution required the addition of 24.80 cm 3 of a 0.550 mol dm –3 solution of hydrochloric acid for complete neutralisation. The equation for the reaction between the metal carbonate and hydrochloric acid is given below. M represents the symbol of the metal: M 2 CO 3 + 2HCl → 2MCl + H 2 O + CO 2 Calculate the relative formula mass of M 2 CO 3 and hence deduce the metal in the carbonate. [4] 9. When 1 kg of sulfur dioxide is reacted with excess oxygen, 1.225 kg of sulfur trioxide is formed: [3] 10. A 0.920 g sample of impure calcium carbonate was added to 40.0 cm 3 of hydrochloric acid of concentration 0.650 mol dm –3 . At the end of the reaction some acid was left unreacted. The unreacted acid required 25.20 cm 3 of sodium hydroxide of concentration 0.325 mol dm –3 for complete neutralisation. (a) Calculate the number of moles of hydrochloric acid used up in the reaction with impure calcium carbonate. [3] (b) Calculate the percentage, by mass, of calcium carbonate in the impure sample. [3] The equations for the reactions are CaCO + 2HCl → CaCl 2 + H 2 O + CO 2 HCl + NaOH → NaCl + H 2 O 2SO 2 (g) + O 2 (g) → 2SO 3 (g) Calculate the percentage yield.

48 DRAFT