Edexcel Jan 2014 (IAL) Paper 6 Q2 (with explained solutions) |

Skip to content

Edexcel Jan 2014 (IAL) Paper 6 Q2

Answers available below

2 Solution B is copper(II) sulfate dissolved in water. (a) When an excess of concentrated hydrochloric acid is added to solution B, the colour of B changes from blue to yellow. Give the formula of the complex ion responsible for the yellow colour. (1)(b) What would you observe as dilute ammonia solution is added, drop by drop, to another sample of solution B? (3)(c) 20.0 cm3 of solution B was added to excess aqueous potassium iodide solution and the volume made up to 250 cm3. The following reaction occurred: 2Cu2+(aq) + 4I(aq) (cid:314) 2CuI(s) + I2(aq) 25.0 cm3 samples of the resulting mixture were titrated with 0.120 mol dm3 sodium thiosulfate solution. The mean titre was 17.85 cm3. (i) Complete the ionic equation for the reaction of thiosulfate ions with iodine. State symbols are not required. 2S2O3 2 + I2 (cid:314)+(ii) Calculate the concentration of solution B, in mol dm3. (1) (3) (Total for Question 2 = 8 marks) *P42975RA0416*<br />
BLANK PAGE *P42975RA0516* Turn over<br />

Show answer

Acceptable Answers Reject Mark 2-/[CuCl4]2- /(CuCl4)2-/[Cu(Cl)4]2- CuCl4 CuCl4 Correct formula with added H20 Acceptable Answers Reject Mark (pale) blue precipitate (1) Ignore gelatinous in front of precipitate but not in front of solution in next part. precipitate dissolves (in excess ammonia)/ precipitate disappears/soluble/solution (1) forms deep/dark(er)/royal blue(solution) (1) deep blue solution forms scores 2nd and 3rd marks Marks stand alone Ignore formulae even if incorrect Acceptable Answers 2- + I2) S4O6 ( 2S2O3 Ignore state symbols even if incorrect 2- + 2I- Just blue Reject Mark Question Number 2(a) Question Number 2(b) Question Number 2(c)(i)<br />
Acceptable Answers Question Number 2(c)(ii) mol S2O3 2- = 17.85 x 0.120/1000 (1) = 2.142 x 10-3/0.002142 mol Cu2+ = 2.142 x 10-3 in 25 cm3 total mol Cu2+= 2.142 x 10-3 x 250/25 (1) = 2.142 x 10-2/0.02142 [CuSO4] = 2.142 x 10-2 x 1000/20.0 = 1.07(1) (mol dm-3 ) Ignore sf except 1 sf Correct answer with no working (3) 0.107 (mol dm-3) 2 max Check unfinished calculation not finished on next page 2nd and 3rd marks can be transferred errors (1) Reject Mark 1 sf 1.0/1 (Total for Question 2 = 8 marks)<br />

Question 1 2 3 4

About us | Need Help? | Feedback

Proudly powered by WordPress | Theme: Sydney by aThemes.