| Date | November 2016 | Marks available | 2 | Reference code | 16N.2.sl.TZ0.4 |
| Level | SL | Paper | 2 | Time zone | TZ0 |
| Command term | Describe | Question number | 4 | Adapted from | N/A |
Question
Magnesium is a group 2 metal which exists as a number of isotopes and forms many compounds.
State the nuclear symbol notation, \({}_Z^AX\), for magnesium-26.
Mass spectroscopic analysis of a sample of magnesium gave the following results:
Calculate the relative atomic mass, Ar, of this sample of magnesium to two decimal places.
Magnesium burns in air to form a white compound, magnesium oxide. Formulate an equation for the reaction of magnesium oxide with water.
Describe the trend in acid-base properties of the oxides of period 3, sodium to chlorine.
In addition to magnesium oxide, magnesium forms another compound when burned in air. Suggest the formula of this compound
Describe the structure and bonding in solid magnesium oxide.
Magnesium chloride can be electrolysed.
Deduce the half-equations for the reactions at each electrode when molten magnesium chloride is electrolysed, showing the state symbols of the products. The melting points of magnesium and magnesium chloride are 922 K and 987 K respectively.
Anode (positive electrode):
Cathode (negative electrode):
Markscheme
\({}_{12}^{26}{\rm{Mg}}\)
«Ar =»\(\frac{{24 \times 78.60 + 25 \times 10.11 + 26 \times 11.29}}{{100}}\)
«= 24.3269 =» 24.33
Award [2] for correct final answer.
Do not accept data booklet value (24.31).
MgO(s) + H2O(l) → Mg(OH)2(s)
OR
MgO(s) + H2O(l) → Mg2+(aq) + 2OH–(aq)
Accept \( \rightleftharpoons \).
from basic to acidic
through amphoteric
Accept “alkali/alkaline” for “basic”.
Accept “oxides of Na and Mg: basic AND oxide of Al: amphoteric” for M1.
Accept “oxides of non-metals/Si to Cl acidic” for M2.
Do not accept just “become more acidic”
Mg3N2
Accept MgO2, Mg(OH)2, Mg(NOx)2, MgCO3.
«3-D/giant» regularly repeating arrangement «of ions»
OR
lattice «of ions»
Accept “giant” for M1, unless “giant covalent” stated.
electrostatic attraction between oppositely charged ions
OR
electrostatic attraction between Mg2+ and O2– ions
Do not accept “ionic” without description.
Anode (positive electrode):
2Cl– → Cl2(g) + 2e–
Cathode (negative electrode):
Mg2+ + 2e– → Mg(l)
Penalize missing/incorrect state symbols at Cl2 and Mg once only.
Award [1 max] if equations are at wrong electrodes.
Accept Mg (g).
