Paper 1-2019

Question 1

CsI enthalpy of atomisation

Answer 1

Cs (s) +1/2 I2(s)

Question 2

Electro spray ionisation

Answer 2

Sample dissolved in polar volatile solvent
Injected through fine needle giving fine mist
Tip of needle= high voltage
Tip of needle gains proton
Solvent dissolves away while ion moves towards -ve plate

Question 3

TOF Calculation

Answer 3

T=d^m/2Ke

Question 4

Period 4 largest atomic radius

Answer 4

Potassium
Smallest no. Of protons/nuclear charge
Similar shielding

Question 5

(Fe(H2O)6)3+ +HCl

Answer 5

[FeCl4]-

Question 6

[Fe(H2O)6]3+ to [Fe(H2O)6]2+ reagent

Answer 6

Xs Zn in acid or KI

Question 7

Nacl and H2SO4
role of H2SO4

Answer 7

NaCl+ H2SO4–> NaHSO4+HCl
Acts as acid or proton donor

Question 8

NaBr and H2SO4 and fumes SO2 formed.
Give observation and role of sulfuric

Answer 8

2NaBr+2H2SO4–>Na2SO4+SO2+Br2+2H2O
Brief fumes
Oxidising agent/ electron acceptor

Question 9

2Ways to reduce %uncertainty of vol of Sodium thiosulfate keeping apparatus same

Answer 9

Use more alloy
Decrease conc/mass of Sodium thiosulfate

Question 10

Why is CuI white

Answer 10

Completed/Full 3d subshell
Cannot absorb visible light

Question 11

How to deduce forward reaction is endothermic with Kp and temp

Answer 11

As Kp increases as does temperature. The larger the temp the greater the amount of products. At higher temps more dissociation occurs

Question 12

Bp of ethanol and methoxymethane (78° and -24°)

Answer 12

Ethanol- h bonding
Metho- vdw/ permanent dipole dipole
H bonding is stronger therefore requires more energy to overcome

Question 13

Shake of ClF4 and ba

Answer 13

Square planar
90°

Question 14

Half neutralisation

Answer 14

See where curve goes steep and do 1/2 that volume and then go up to ph mark

Question 15

Expression for buffer solution that has constant PH even when diluted

Answer 15

[HA]/[A-]