a level 2024 quetsions

Question 1

Give two differences between the modern model of an atom and the Thomson model of an atom.

Answer 1

protons in the centre of the atom/nucleus
electrons are in shells/energy levels (around the nucleus)
neutrons in the centre of the atom/nucleus
most of the atom is empty space/most of mass in nucleus

Question 2

Tellurium has a relative atomic mass of 127.6
Iodine has a relative atomic mass of 126.9
Define relative atomic mass.
Suggest one property of tellurium that justifies its position before iodine in the
modern Periodic Table

Answer 2

Average / mean mass of 1 atom (of an element) (1)
1/12 mass of one atom of 12C (1)

Question 3

A sample of tellurium is analysed in a time of flight (TOF) mass spectrometer using
electron impact ionisation.
Give an equation, including state symbols, for this ionisation.

Answer 3

Te(g) + e– → Te+(g) + 2 e–

Question 4

Suggest why the solution is kept until no more solid needs to be added

Answer 4

To ensure that) the solution/it is saturated

Question 4

Which statement about kinetic energy (KE) is correct?

The KE of 126Te+ is greater than the KE of 124Te+
The KE of 126Te+ is the same as the KE of 124Te+
The KE of 126Te+ is less than the KE of 124Te+

Answer 4

The KE of 126Te+ is the same as the KE of 124Te+

Question 5

Suggest why it is important to remove the undissolved strontium hydroxide before the
titration

Answer 5

Otherwise, the titre would be larger
Or
Would need a larger volume of acid/HCl
Or
Because undissolved strontium hydroxide will react (with the
acid/HCl)

Question 6

After the filtration, the solution is stored in a stoppered flask.
Suggest a reason for stoppering the flask.

Answer 6

To prevent reaction with carbon dioxide (in the air)
OR
To prevent evaporation (of water/from solution)

Question 7

Give an equation to show how chlorine forms an acidic solution in water.

Answer 7

Cl2 + H2O ⇌ HCl + HOCl

Question 8

Give an equation for the reaction between chlorine and
cold, dilute aqueous sodium hydroxide

Answer 8

Cl2 + 2 NaOH ⟶ NaCl + NaOCl + H2

Question 8

Give the equation for the reaction of solid sodium chloride with
concentrated sulfuric acid.
State the role of the chloride ions in this reaction.

Answer 8

NaCl + H2SO4 ⟶ HCl + NaHSO4
base/proton acceptor

Question 9

Chlorine forms an ion with the Group 3 element thallium (Tl).
State and explain the bond angle in TlCl2
+

Answer 9

180°
(2) bond pairs repel to be as far apart as possible

Question 10

State the meaning of the term perfect ionic model

Answer 10

(Ions are) point charges
Or
(Ions are) perfect spheres
Or
No covalent character

Question 11

State why the atomic radius of calcium is greater than the atomic radius of
magnesium.

Answer 11

more shells
Or
more energy levels

Question 12

Explain why the enthalpy of lattice dissociation for sodium oxide is greater than the
enthalpy of lattice dissociation for sodium chloride

Answer 12

Oxide ions
M1 have higher (negative) charge
stronger attraction between (O2– and Na+/oppositely charged)
ions

Question 13

Magnesium reacts with steam.
Give an equation, including state symbols, for this reaction.

Answer 13

Mg(s) + H2O(g) ⟶ MgO(s) + H2(g)

Question 14

Similar-sized pieces of barium and magnesium are added to separate
100 cm3 samples of dilute sulfuric acid. In each case the sulfuric acid is in excess.

Explain why
* the barium initially reacts more quickly than the magnesium
* the barium reaction stops before all the barium has reacted

Answer 14

Ba is more reactive) because outer/valence electrons further
from nucleus/less attracted to the nucleus/lost more easily
M2 Insoluble barium sulfate (is formed)
Barium sulfate prevents further reaction (with sulfuric acid)

Question 15

Sodium reacts with aluminium and hydrogen to form solid NaAlH4
Give an equation for this reaction.
Suggest why NaAlH4 has a high melting point.

Answer 15

M1 Na + Al + 2 H2 → NaAlH4
M2 contains oppositely charged ions/ Na+ and AlH4
– ions
M3 strong attraction between (oppositely charged) ions

Question 16

Give the equation for the reaction between H3PO4 and an excess of NaOH

Answer 16

3 NaOH + H3PO4 → Na3PO4 + 3 H2O

Question 17

In a lithium cell, a lithium cobalt oxide electrode and a lithium electrode are used.
Give the equation for the reaction that occurs at the positive electrode.

Answer 17

Li++ CoO2 + e–
→ Li+(CoO2)–

Question 18

Commercial electrochemical cells can be rechargeable or non-rechargeable.
State why lithium cells can be recharged.

Answer 18

The electrode reactions can be reversed (by applying a reverse
potential)