Question

Sodium carbonate, Na2CO3, reacts with hydrochloric acid, HCl, to produce sodium chloride, carbon dioxide and water. Refer to slide 7.18 for a summary of formulae relevant to the calculations below. 2HCl(aq) + Na.CO3(aq) + NaCl(aq) + H2O(l) + CO2(g) 1. Use this reaction to explain what is meant by the terms "acid", "conjugate base" and "salt" 2. Balance the equation for this reaction. 3. A solution was prepared by dissolving 5.00 g of Na2CO3 in water and adding water to give 250 mL of solution. Calculate the amount concentration (molarity) of that solution. The Na2CO3 solution described above was used to analyse a hydrochloric acid solution of unknown concentration. It was found that 24.30 mL of the Na-CO3 solution was required to neutralise a 20.00 mL sample of the hydrochloric acid solution. 4. Using your answer to part 3 above, calculate the amount of Na,Co, present in 24.30 mL of the Na2CO: solution. 5. Using your answer to part 2 above, deduce the amount of HCl that was present in the 20.00 mL sample of the HCl solution. 6. Using your answer to part 5 above, calculate the amount concentration of the HCl solution. 7. Assuming that 1 mol of CO2 occupies 24.1 L at room temperature and pressure (i.e. that the molar volume is 24.1 L mol), calculate the volume of CO, formed in this reaction. 8. Calculate the pH of the HCl solution. 9. Strictly speaking, it is not correct to say that the solutions described above contain HCl or Na,CO3. Explain why, specifying what species are actually present in these solutions.

Answer 1

3 Weight of Naloz - 5.00g. Equivalent weight of Nalo 52.995 glea. lution - 5 x 100 ot. pd 52.995x 250 11 terw zde 0-3714 N longe som had op Molanity 0.3774 x 2 imed a pinirish story do lo e : K 2-1 mod 0.7548 M to remont 033 mil 1000 ml. Na, co solution contains Join an hour 0.7528 Mols of Na, co meitas soll im of Waco, solution contains 0-7548 mols of Nae 0 135 000 77 1000 24.30 ml of Nato solution contains 0.7548, 24.30 1000 0.0183 mols of Nazcoz

Molar mass of Nacos = 105.988 g/mol 0.0183 mols of Na, con contains pow. 0.0183 x 105.988 (1.9395 g of Nazcoa Normality of Naco, solution (N.) = 0.37740 Volume of a co solution (v.) = 24.30 ml. Volume of Hel solution () 20 ml Normality of Hell solution - 0-3774x24-30 20 Yes foot 0.4555 N molanty of Hel solution 0.4585 0.4585 M 1000 mL of HCl solution - 0.4585 mols of Hell :: qo ml of Hel solution: 0:4585 x 20 2000 sash 0.00917 mols

molar mass of HCl 2 36.4609 g/mol 0.00917 mols of HCl soolermoon contains : 0.00917 * 36.4609 : 0.3343 g of 14c/ © Amount concentration of 141 0:4565 M nostalo From the balanced eacration it is clear that 2 mols of Hcl ereacts with 1 mol of Na coz to form Imol CO2 Thus 0.00911 mols of lich reacts to give Lx0.00917 1 0.004585 mols of co₂ mol of co occupics 24.12 of volume.

0.004685 mols of CQ, Occupies 0.004585 * 24.1 - 0.1104 L ® pH. -log CW*] &– log C 0.4585) 0.338 (9) Hel and Na,eo, dissociates in water Cionisation) to give itt, et, Nat and coor ions.