chemistry paper 3

Question 1

Show thermally stable

Answer 1

Calculate 🔺total from 🔺system + 🔺surroundings
If positive feasible

Question 2

Temp at which reaction is feasible

Answer 2

🔺system = enthalpy change / temp

Question 3

Thermal stability

Answer 3

Size of ion/charge
Ability to polarise the bond

Question 4

Barium carbonate and sulphuric acid

Answer 4

Not soluble

Question 5

Why cold water in filtration

Answer 5

Less soluble in cold water so dosent dissolve

Question 6

Mass of electron

Answer 6

1/1840

Question 7

how london bonds form

Answer 7

uneven distribution of electrons results in a temporary dipole which induces a temporary dipole on another molecule

Question 8

stronger london forces

Answer 8

more electrons and shells of electrons so greater dipole and therefore stronger bonds

Question 9

TMS and why used

Answer 9

(CH3)4Si
-single peak
-dosent overlap with other peaks
-low boiling temp so can easily be removed
-strong signal so only small amount needed

Question 10

why e/z isomer

Answer 10

 restricted / limited rotation (about the C=C double bond)
each carbon atom in the double bond is attached to (two)
different atoms / different groups (of atoms) / to a H (atom)
and a COOH group

Question 11

acid

Answer 11

proton donor
becomes more negative

Question 12

base

Answer 12

proton acceptor
becomes more positive

Question 13

ammonium

Answer 13

NH4

Question 14

drying agent

Answer 14

anhydrous sodium sulphate

Question 15

what happens when two compounds in flame test

Answer 15

stronger one masks other

Question 16

why is wire heated in flame tests

Answer 16

to remove previous sample residue

Question 17

why does the fume cupboard need to be down

Answer 17

(window) above the safety line means the exhaust system
is not strong enough to draw in the fumes
 so the toxic fumes will escape (into the laboratory)

Question 18

esterfacation with carboxilic acid compared to acyl chloride

Answer 18

acyl chloride - irreversable
forms hcl
fast at room temp
carboxylic acid -
reversable
forms water
needs acid catalyst

Question 19

why complex ions coloured

Answer 19

(ligand causes d orbitals to split (into 2 energy levels)
 energy in the visible region absorbed to promote electrons to
higher d orbitals
 the remaining light is the complementary colour emitted

Question 20

dimer

Answer 20

bonded with dative bonds

Question 21

impurities on boiling temp

Answer 21

decrease and makes less sharp