last minute practical exam revish

Question 1

define heating under reflux

Answer 1

• boiling reaction mixture

- using condenser to cool the vapour and return it to reaction mixture in flask

Question 2

General method to work out percentage yield?

Answer 2

Actual yield (g)/ Theoretical yield (g) x 100

Question 3

0.40 g of pure hexane-1,6-dioic acid (Mr = 146) are obtained from 2.0 g of nylon-6,6.
Calculate the percentage yield of the reaction.

Answer 3

31%

Question 4

They carry out an experiment in which a known mass of magnesium carbonate is heated and the gas
evolved is collected in a 100 cm3
gas syringe. The apparatus is allowed to cool to room temperature
and the volume of the gas collected is measured.
(i) What is the maximum mass of magnesium carbonate that could be used in this
experiment?

Answer 4

0.351g

Question 5

What’s thermal decomposition?

Answer 5

When a substance breaks down when heated

Question 6

What do group 2 carbonates decompose to form?

Answer 6

CO2 and Metal oxide

Question 7

If you start off with the same mass of 2 group 2 metal carbonates, how does the CO2 produced during thermal composition + why?

Answer 7

The volume of CO2 decreases going down group 2 as the Mr of the metal gets bigger so a smaller number of MCO3 moles is contained in the same mass