2023 Chem Qs

Question 1

Explain why the structure of magnesium gives it a high melting temperature (2)

Answer 1

Giant metallic lattice

Strong electrostatic forces of attraction

Question 2

Hazard symbol that potassium manganate is liable to
A B C D

Answer 2

D - react vigorously with reducing agents

Question 3

State what is meant by electronegativity (1)

Answer 3

Ability of an atom to attract a PAIR OF ELECTRONS

Question 4

Explain the trend of electronegativity for group 7 elements (3)

Answer 4

LESS ELECTRONEGATIVE

Pair of electrons are further away from the nucleus

MORE shielding electrons

Question 5

Describe what you understand about ‘continuum of bonding types’ in relation to electronegatives (2)

Answer 5

Continuum of bonding has COVALENT AND IONIC

electronegativity differences between two atoms of intermediate value= intermediate bonding

Question 6

8KI + 5H2SO4 -> 4I2 + 4K2SO4 +H2S + 4H2O

State what is oxidation and what is reduction (1)

Which of the species is the oxidising agent and which is the reducing agent (2)

Answer 6

Oxidation = LOSS
Reduction GAIN

I in KI is the REDUCING agent as it loses one electron

H2SO4 is the OXIDISING AGENT as each Sulfur gains 8 electrons

Question 7

_Br2 + _OH- -> BrO3- + _ + _

Complete the equation and justify the balancing of the equation in terms of changes in the oxidation number (4)

Answer 7

3Br2 + 6OH -> BrO3- + 5Br- + 3H2O

Bromine changes from 0 to 5+ and 1+

There must be 5 bromide ions Br- for each bromate ion BrO3-

Question 8

Deduce the increasing size of ions (4)

Br-, Ca2+, Cl-, K+

Answer 8

Ca2+, Cl- and K+ are ISOELECTRONIC

Br- is the largest as it has one more shell of electrons

From Cl- to K+ to Ca2+ MORE PROTONS IN NUCLEUS

smallest = Ca2+ < K+ <Cl-< Br- largest

Question 9

A major inaccuracy CO2 is lost before the bung is replaced.

Identify a change to the acid in Step 1 that would reduce the volume of gas lost between steps 5 and 6 (2)

Answer 9

DECREASE concentration of nitric acid and use a weak acid instead

DECREASE in reaction rate would result in slower formation of CO2

Question 10

Identify a change in steps 5 and 6 that would prevent loss of gas (2)

Answer 10

Use a container to contain the CaCO3

Replace the bung then SHAKE the conical flask so substances mix

Question 11

A second source of inaccuracy is significant solubility in water of CO2

Give two improvements which together prevent this problem (2)

Answer 11

Use a gas syringe

Bubble CO2 through nitric acid to SATURATE the solution

Question 12

Write the equation of the second ionisation energy of Beryllium (2)

Answer 12

Be+ (g) -> Be2+ (g)+ e-

Question 13

explain how the nuclear structure and electronic structure of Group 2 elements affect ionisation energies (6)

Include: - first ionisation energies down the group

• a comparison of the first two ionisation energies for an element

Answer 13

M1- ionisation is LESS ENDOTHERMIC DOWN the group

M2- ELECTRONS are removed from a shell further from the nucleus

M3- electrons are MORE SHIELDED (more repulsion from inner electrons)

M4- NUCLEAR CHARGE IS GREATER down the group

M5- the second ionisation energy is MORE ENDOTHERMIC as electrons are being removed from the SAME SUBSHELL

M6- second ionisation energy LESS REPULSION THAN THE FIRST IONISATION ENERGY

Question 14

Explain how this changing value (Group 2) might contribute to the relative reactivity of the elements with chlorine (2)

Answer 14

Sum of the first two ionisation energies DECREASES down the group so reactivity INCREASES with Cl-

because group 2 elements form ionic bonds by losing 2 outer electrons