STAV 09 trial exam questions help

[mystikal]

Question 20 of Multiple Choice
can someone explain to me how that works?

Question 5 e)
I just put down it is going to be less due to the increase in molar mass, the answer said it is approximately half, do i still get the mark?

Question 6 b)
I put down distillation for the answer because it says "pure", but the answer is fractional distillation, do i get the mark?

Also what does it mean by 'percentage yield'

[mystikal]

o yea i forgot to ask that if it asks for semi structral formula can we still put ch2=ch2 like showing the double bond like that?

[d0minicz]

yeah you can for the CH2=CH2
Percentage yield is where you calculate how mcuh you actually obtained ; and compare it to what was expected to be produced, which you work out through mole ratio and find mass etc.
obtained/expected x100% = percentage yield

[chem-nerd]

MCQ20

steps 2, 4 and 5 are fine

step 1 would cause c(acid) to be lower -> the titre would be higher -> c(base) would be calculated higher

step 3 would cause n(base) to be higher -> titre would be higher -> c(base) would be calculated higher

thus the answer is C