june 2022 paper 1 incorrect answers

Question 1

explain the third ionisation energy of magnesium is much higher than the second ionisation energy of magnesium

Answer 1

M1: electron is removed from the 2p subshell
M2 : fewer shielding and increased attraction between nucleus and outer electrons

Question 2

explain why CBr4 is not a polar molecule

Answer 2

M1 : there is an equal distribution of of electron density
M2 : so dipoles cancel out

Question 3

suggest, in terms of intermolecular forces for each compound, why CBr4 has a higher boiling point than CHBr3

Answer 3

M1 : CBr4 has van der waals forces between molecules
M2 : CHBr3 has van der waals and dipole dipole forces
M3 : the van der waals between CBr4 molecules are stronger than the dipole dipole and van der waals forces between CHBr3 because it has more electrons

Question 4

In acidic solution, IO3- ions oxidise iodide ions to iodine
deduce the half equation to show the reduction process in the reaction

Answer 4

2IO3- + 12H+ + 12e- — I2 + 6H2O

Question 5

when iodide ions are oxidised using concentrated sulfuric acid, sulphur dioxide, a yellow solid and a foul smelling gas are all formed
Give an equation to show the reaction between iodide ions and concentrated sulphuric acid to form yellow solid
Identify foul smelling gas

Answer 5

equation : 6I- + 6H+ + H2SO4 — S + 3I2 + 4H2O

Question 6

state whether the forward reaction in this equilibrium results in an increase, decrease or no change in the amount, in moles of gas

Answer 6

M1 : increase
M2 : lower yield at higher pressure
M3 : equilibrium has shifted backwards

Question 7

explain why a catalyst has no effect on percentage yield

Answer 7

increases the rate of forward and reverse reactions equally

Question 8

explain how you would test for CO2

Answer 8

bubble through limewater and precipitate forms

Question 9

describe a series of tests that the student can use to show that solution C contains ammonium sulfate

Answer 9

ammonium : warm and add NaOH, hold damp red litmus at the mouth of tube and it should turn blue
sulfate : add acidified BaCl2 and white precipitate forms

Question 10

explain how the masses recorded during this experiment can be used to show that solution D contains a mixture of halide ions

Answer 10

M1 : the 2nd mass is smaller
M2 : AgCl dissolves in dilute ammonia