The questions are on the periodic table groups test. Take it under real conditions before reading the mark scheme.
Quick answer: Group 1 metals have one outer electron and become more reactive down the group, reacting with water to make hydrogen and an alkaline hydroxide. This mark scheme gives the model answers and the marks for the 8 questions of the Chemistry 9-10 test on periodic table groups, from potassium in water to halogen atoms, with the equivalent answers to accept.
This is the periodic table groups test answers for chemistry grades 9-10, with the marks for each answer. First sit the test without notes, then mark it here and revise with the lesson.
Each model answer is followed by the marking points. Accept any correct equivalent wording and award marks for correct reasoning even when a number is slightly off.
Level: Chemistry grades 9-10 (GCSE · IGCSE · O Level · Class 9-10) · Curriculum: GCSE C1, IGCSE 9
Periodic table groups test answers: answers and marks
Question 1 Potassium in water (3 marks)
Any three: it floats; it melts into a ball; it fizzes or gives off gas; it moves around the surface; a lilac flame appears; it gets smaller and disappears.
Marking: 1 mark each, up to 3.
Question 2 Equation for potassium (3 marks)
2K(s) + 2H₂O(l) → 2KOH(aq) + H₂(g). The solution is alkaline with a pH greater than 7 (about 13 to 14).
Marking: 1 mark correct formulae; 1 mark balanced with state symbols; 1 mark alkaline.
Question 3 Halogens in appearance (2 marks)
Chlorine is a pale green gas. Iodine is a grey solid (it gives a purple vapour).
Marking: 1 mark for each halogen.
Question 4 Bromine and sodium iodide (3 marks)
(a) The solution turns from orange to brown.
(b) Br₂ + 2NaI → 2NaBr + I₂
(c) Bromine is more reactive than iodine, so it displaces iodine from its salt.
Marking: 1 mark each.
Question 5 Noble gases (2 marks)
Argon has a full outer shell of electrons, so it does not lose, gain or share electrons. One use: filling filament lamps or shielding welds.
Marking: 1 mark for the full outer shell; 1 mark for a correct use.
Question 6 Alkali metal trend (3 marks)
Both have one outer electron. In caesium the electron is in a shell much further from the nucleus. It is also shielded by more inner shells, so it is held weakly and lost more easily.
Marking: 1 mark further from nucleus; 1 mark more shielding; 1 mark lost more easily.
Question 7 Mass of sodium bromide (2 marks)
n(NaBr) = 2 × 0.0500 = 0.100 mol. Mass = 0.100 × 103 = 10.3 g.
10.3 g
Marking: 1 mark for the mole ratio; 1 mark for the mass.
Question 8 Halogen atoms (2 marks)
Chlorine has fewer shells, so the electron it gains enters a shell closer to the nucleus. There is less shielding, so the attraction is stronger.
Marking: 1 mark closer to the nucleus; 1 mark less shielding or stronger attraction.
