C2H Edexcel Pixl Mark Scheme November 2014

C2H Edexcel PiXL Mark Scheme November 2014

Question / Answer / Additional Guidance
1 (a) / B periods (1) / Score 0 marks if more than one box is crossed
1 (b) / Same number of protons/electrons (1) but different numbers of neutrons (1)
1 (c) / (63 x 69) + (31 x 65) / 100 (1)
63.62 (1)
64 (1) / Award 2 marks for 63.62 or 63.6 with no working shown
Award 3 marks for 64 with no working shown
1 (d) / Electronic shells for calcium with 20 electrons correctly drawn with dots or crosses with no errors (2) / Allow 1 mark for no more than two errors
1 (e) / The number of electrons in the outer shell (1) is the same as the group number in the periodic table (1) / Allow ‘valence electrons’
(Total for Question 1 = 10 marks)
2 (a) (i) / MgCl2 (1)
2 (a) (ii) / CuSO4 (1)
2 (b) / Any two from:

The sodium chloride ions are packed together

Strong electrostatic forces of attraction

Between oppositely charged ions

(2)
2 (c) / D an insoluble product formed in a precipitation reaction
(1) / Score 0 marks if more than one box is crossed
2 (d) / Pb(NO3)2 (aq) + 2KI (aq) → PbI2(s) + 2KNO (aq) (3) / 1 mark for formulae
1 mark for balancing
1 mark for state symbols
Allow = sign instead of →
(Total for Question 2 = 8 marks)
3 (a) / A chromatogram (1) / Score 0 marks if more than one box is crossed
3 (b) / 2 (1)
3 (c) (i) / X placed accurately (1)
3 (c) (ii) / It has moved furthest up the paper (1)
3 (d) / 4/10 (1)
0.4 (1) / 0.4 on its own gains 2 marks
3 (e) / Any 2 from:

Identifying food colourings
Analyse DNA
Analyse paints/dyes

(2) / Accept correct alternative uses
(Total for Question 3 = 8 marks)
4 (a) / 17 (1)
4 (b) / Hydrogen 1.2 / 1 = 1.2 Oxygen 9.6 / 16 = 0.6 (1)
Hydrogen 1.2/0.6 = 2 Oxygen 0.6/0.6 = 1 (1)
H2O (1) / Each of the steps must be followed and a candidate can only gain one mark for just writing H2O with the empirical formula not calculated.
4 (c) / 14 / (14 + 4 + 35.5) x 100 (1)
26 (1) / 26 on its own gains 2 marks
4 (d) / Relative formula mass of NaOH = 40
Relative formula mass of NaCl = 58.5 (1)
NaOH: 40/40 = 1 NaCl: 58.5/40 = 1.4625 (1)
Multiply both sides by 5 (1)
NaOH = 5g NaCl = 7.3 or 7.31 (1) / 7.3 or 7.31 on its own gains 4 marks
(Total for Question 4 = 10 marks)
5 (a) / Carbon dioxide (1) / Allow CO2 but ignore if written incorrectly
5 (b) (i) / Any number greater than 0 but less than 3 (1) / Allow 0-3 (minutes)
5 (b) (ii) / 5 (1) / Allow any number between 4.5 and 5 (minutes) inclusive
5 (b) (iii) /

Line to the left of the original (showing faster initial rate) (1)
Line finishing higher than original (showing greater volume evolved (1)

5 (c) / C exothermic(1) / Score 0 marks if more than one box is crossed
5 (d) / Indicative content:
Higher Temperature

As you increase the temperature, the particles move quicker
The particles collide more frequently
With more energy
Therefore more successful collisions are likely

Larger Surface Area

The larger the surface area, the more particles are exposed
The particles collide more frequently
Between the reactants
Therefore more successful collisions are likely

/ Mark the answer according to the levels below. Identify the level first of all, then award the top of the mark band if the student’s literacy is generally good or the bottom if there are many literacy errors.
Accept higher level answers.
Level / Level Description / Marks
0 / No relevant answer. / 0
1 / Simple explanation about the effect of increasing the temperature or surface area on the rate of reaction. / 1-2
2 / Simple explanation about the effect of increasing the temperature and surface area on the rate of reaction. / 3-4
3 / Detailed explanation about the effect of increasing the temperature and surface area on the rate of reaction. Correct scientific terminology is used and the candidate’s answer flows well in a clear logical order. / 5-6
(Total for Question 5 = 12 marks)
6 (a) / C 7 (1) / Score 0 marks if more than one box is crossed
6 (b) / Gas (1)
6 (c) / 2K (s) + Br2(l) → 2KBr (s)
(3) / 1 mark for formulae
1 mark for balancing
1 mark for state symbols
Allow = sign instead of →
6 (d) / A 1 (1) / Score 0 marks if more than one box is crossed
6 (e) / Indicative content:
Descriptions

Lithium is less reactive compared to sodium and potassium
Potassium is the most reactive compared to sodium and lithium
Lithium fizzes
Sodium is melted
Potassium catches fire
The reactivity of alkali metals increases as you go down the group

Explanations

The elements at the bottom of group 1 have more electrons
They have more shells in their atoms
Their outer electrons are further away from the influence of the nucleus
The force between the positive and negative charges are weaker
This causes their outer electron to be lost more easily