tricky PPQ's

Question 1

Uncertainty of a burette

Answer 1

Complicated so they will give you a total uncertainty. You just calculate % uncertainty then doing uncertainty/volume measured from burette times by 100.
They say you have 2 readings and error value, ignore that as don’t to times by 2 as they’ve already calculated this with the total uncertainty they gave you.

Question 2

Long answer NMR questions

Answer 2

need to say structure giving each peak and what it is next to
e.g. peak at 3.95, tripley (integration 2) Cl-CH2 next to CH2.

Question 3

Atoms in a molecule will be in same plane if:

Answer 3

Have double or triple bond since they can’t rotate due to having a pi bond.
Also if trigonal or square planar

Question 4

BF3 non polar because

Answer 4

Symmetrical shape

Question 5

NH4 polar because

Answer 5

Tetrahedral but one dative bond so dipoles don’t cancel out

Question 6

NH3 polar because

Answer 6

Dipoles don’t cancel as tetrahedral shape but one lone pair