Question
The periodic table provides information about electron configuration, and physical and
chemical properties of elements.
(a) Bismuth has atomic number 83. Deduce two pieces of information about the electron configuration of bismuth from its position on the periodic table.
(b) Outline why aluminium is malleable.
(c) An 11.98g block of pure aluminium was heated. Calculate the heat energy absorbed, in J, to increase its temperature from 18.0°C to 40.0°C. The specific heat capacity of aluminium is 0.902J \(g^{−1} K^{−1}\).
(d) Argon has three naturally occurring isotopes, \(^{36}Ar\), \(^{38}Ar\) and \(^{40}Ar\).
(i) Identify the technique used to determine the relative proportions of the isotopes of argon.
The isotopic composition of a sample of argon is 0.34% of \(^{36}Ar\), 0.06% of \(^{38}Ar\) and 99.6% of \(^{40}Ar\).
(ii) Calculate the relative atomic mass of this sample, giving your answer to two decimal places.
Answer/Explanation
Answer:
(a) Any two ofthe following:
«group 15 so Bi has» 5 valence electrons
«period 6 so Bi has» 6 «occupied» electron shells/energy levels
«in p-block so» p orbitals are highest occupied
occupied d/f orbitals
has unpaired electrons
has incomplete shell(s)/subshell(s)
(b) «layers of» cations slide over each other without disrupting bonding
OR
attraction between metal ions and delocalized electrons/metallic bonding is not
disrupted by changing position of metal ions
OR
metallic bonds are non-directional
OR
changing the shape does not disrupt the bonding
(c) «heat energy = 11.98 g x 0.902 J \(g^{−1} K^{−1}\) x 22.0 K =» 238 «J»
(d) (i) mass spectrometry
OR
mass spectroscopy
OR
mass spectrum
OR
MS
(ii) (0.0034 x 36) + (0.0006 x 38) + (0.996 x 40)
39.99
Question
When heated in air, magnesium ribbon reacts with oxygen to form magnesium oxide.
(a) (i) Write a balanced equation for the reaction that occurs. [1]
(ii) Identify a metal, in the same period as magnesium, that does not form a
basic oxide. [1]
(b) The reaction in (a)(i) was carried out in a crucible with a lid and the following data
was recorded:
Mass of crucible and lid = 47.372 ±0.001g
Mass of crucible, lid and magnesium ribbon before heating = 53.726 ±0.001g
Mass of crucible, lid and product after heating = 56.941 ±0.001g
(i) Calculate the amount of magnesium, in mol, that was used. [1]
(ii) Determine the percentage uncertainty of the mass of product after heating. [2]
(iii) Assume the reaction in (a)(i) is the only one occurring and it goes to completion,
but some product has been lost from the crucible. Deduce the percentage yield of
magnesium oxide in the crucible. [2]
(c) 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)
(i) Evaluate whether this, rather than the loss of product, could explain the yield
found in (b)(iii). [1]
(ii) Suggest an explanation, other than product being lost from the crucible or
reacting with nitrogen, that could explain the yield found in (b)(iii). [1]
(d) The presence of magnesium nitride can be demonstrated by adding water to the
product. It is hydrolysed to form magnesium hydroxide and ammonia.
(i) Calculate coefficients that balance the equation for the following reaction. [1]
(ii) Ammonia is added to water that contains a few drops of an indicator. Identify an
indicator that would change colour. Use sections 21 and 22 of the data booklet. [1]
(iii) Determine the oxidation state of nitrogen in Mg3N2 and in NH3. [1]
(iv) Deduce, giving reasons, whether the reaction of magnesium nitride with water is
an acid–base reaction, a redox reaction, neither or both. [2]
(e) Most nitride ions are 14N3- .
(i) State the number of subatomic particles in this ion. [1]
(ii) Some nitride ions are 15N3-. State the term that describes the relationship between 14N3- and 15N3-. [1]
(iii) The nitride ion and the magnesium ion are isoelectronic (they have the same
electron configuration). Determine, giving a reason, which has the greater
ionic radius. [1]
(iv) Suggest, giving a reason, whether magnesium or nitrogen would have the greater
sixth ionization energy. [1]
(f) Suggest two reasons why atoms are no longer regarded as the indivisible units of matter. [2]
(g) State the types of bonding in magnesium, oxygen and magnesium oxide, and how the
valence electrons produce these types of bonding. [4]
Answer/Explanation
Ans.
