2023 A Level H2 Chem Paper 1 Solutions Q01 to Q10
2023 A Level H2 Chemistry Paper 1 Suggested Solutions - Questions 1 to 10
Question 1
Answer: B
Topic: Atomic Structure
Explanation:
Lanthanoids neodymium, Nd, has 60 protons while promethium, Pm, has 61 protons.
We can determine Nd2+ has 85 neutrons and 58 electrons while Pm3+ has 84 neutrons and 58 electrons.
Hence Nd2+ has more neutrons and both ions have the same number of electrons.
Question 2
Answer: C
Topic: Chemical Bonding
Explanation:
The bigger the difference in electronegativity between 2 atoms in a bond, the stronger the ionic character.
Hence YCl has greater ionic character than ZO2 since Y-Cl bond has a greater difference in electronegativity than Z-O bond.
Question 3
Answer: C
Topic: Chemical Bonding
Explanation:
Bromine atom has more electrons than chlorine atom, CH3Br has a bigger and more polarisable electron cloud, stronger instantaneous dipole - induced dipole attraction between molecules, need more energy to overcome hence higher boiling point than CH3Cl.
Question 4
Answer: D
Topic: Chemical Bonding
Explanation:
By considering the number of electrons around central atom via their dot-cross diagrams, we can determine nitrogen in NH4+, carbon in CO2 and carbon in HCHO all have 8 shared electrons.
Question 5
Answer: B
Topic: Chemical Bonding
Explanation:
C-F bond is polar and has dipole moment along its bond.
By considering the shape of molecules and their dipole moments due to C-F bonds, we can determine 1,1-difluoroethene and cis-1,2-difluoroethene are polar.
Question 6
Answer: D
Topic: Atomic Structure
Explanation:
We have to draw out the valence shell electronic configuration via electron in box diagram for Period 3 elements.
From the electronic configurations we can determine that:
P - number of elements with only 1 half filled orbital are Na, Al, Cl (3 elements)
Q - number of elements with only 1 fully filled orbital are Mg, Al, Si, P (4 elements)
Question 7
Answer: A
Topic: Group 2 Elements
Explanation:
Statement 1 is true as down the group, E value is more negative, metals are more likely oxidised hence more reducing.
Statement 2 is true as down the group, size of metal cation increases and charge density decreases. Metal cations become less polarising and distort electron cloud of carbonate to a smaller extent. The bonds within carbonate are relatively more stable and need more energy to break. Hence thermal stability increases.
Statement 3 is false as charge density of cation should decrease due to increasing size of cation.
Question 8
Answer: C
Topic: Atomic Structure
Explanation:
Percentage abundance of 28Si is 92.23%
Let percentage abundance of 29Si be x%, hence percentage abundance of 30Si is (7.77 - x)%
We can then determine relative atomic mass in terms of x and solve for x.
Question 9
Answer: A
Topic: Energetics
Explanation:
NaOH is the limiting reagent so 0.1 mol of NaOH will form 0.1 mol of water.
Heat absorbed by solution = mass of water (150) x c (4.18) x change in temperature (9) = 5.643 kJ = heat released by neutralisation.
Hence enthalpy change of neutralisation can be solved.
Question 10
Answer: A
Topic: Chemical Bonding
Explanation:
Lattice energy is directly proportionate to charge of cation x charge of anion and inversely proportionate to radius of cation + radius of anion.
Ca+ has smaller charge and bigger size hence lattice energy of CaCl should be the smallest.
Mg2+ has bigger charge and smaller size hence lattice energy of MgCl2 should be the largest.
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