Question 22M.2.hl.TZ1.1c(i)
| Date | May 2022 | Marks available | [Maximum mark: 1] | Reference code | 22M.2.hl.TZ1.1c(i) |
| Level | hl | Paper | 2 | Time zone | TZ1 |
| Command term | Evaluate | Question number | c(i) | Adapted from | N/A |
When heated in air, magnesium ribbon reacts with oxygen to form magnesium oxide.
When magnesium is burnt in air, some of it reacts with nitrogen to form magnesium nitride according to the equation:
3 Mg (s) + N2 (g) → Mg3N2 (s)
Evaluate whether this, rather than the loss of product, could explain the yield found in (b)(iii).
[1]
yes
AND
«each Mg combines with N, so» mass increase would be 14x which is less than expected increase of 16x
OR
3 mol Mg would form 101g of Mg3N2 but would form 3 x MgO = 121 g of MgO
OR
0.2614 mol forms 10.536 g of MgO, but would form 8.796 g of Mg3N2 ✔
Accept Yes AND “the mass of N/N2 that combines with each g/mole of Mg is lower than that of O/O2”
Accept YES AND “molar mass of nitrogen less than of oxygen”.
Poorly done. The question asked to evaluate and explain but instead many answers simply agreed with the information provided instead of assessing its strength and limitation.
