✨Module 2: Amount of substance

Question 1

Define mole.

Answer 1

Amount of any substance containing 6.02 x 10^23 particles.

Question 2

One mole of carbon is …

Answer 2

Mass 12g.

Question 3

Define Avogadro’s constant.

Answer 3

No. atoms per mole in 12g of carbon-12.

Question 4

Particles =

Answer 4

Moles x 6.02x10^23

Question 5

Define molar mass.

Answer 5

Mass per mole of substance. gmol-1

Question 6

Moles =

Answer 6

Mass in g/molar mass

Question 7

Define molar gas volume.

Answer 7

Gas volume per mole at a stated temp and pressure. At RTP, it is 24dm3mol-1.

Question 8

RTP is …

Answer 8

20 degrees C and 101kPa.

Question 9

Volume in dm3 =

Answer 9

Moles x 24dm3/24000cm3

Question 10

Moles =

Answer 10

Conc (moldm-3) x volume in solution (dm3)

Question 11

Temp in Kelvin?

Answer 11

Degrees in C + 273

Question 12

Each 1K rise in temp is the same as …

Answer 12

1 degrees C rise in temp.

Question 13

Binary compound contains …

Answer 13

2 elements - use the name of the 1st element and change the name of the 2nd element to -ide.

Question 14

Polyatomic ions contain …

Answer 14

Atoms of more than 1 element.

Question 15

Nitrate/nitrite -
Manganate -
Phosphate -
Hydrogen carbonate -

Answer 15

NO3-/NO2-
MnO4-
PO43-
HCO3-

Question 16

What does (aq) state symbol mean?

Answer 16

Dissolved in water.

Question 17

Rules for balancing equations?

Answer 17

Can use decimals, always use state symbols.

Question 18

Nitrogen/phosphorus/sulfur.

Answer 18

N2, P4, S8.

Question 19

Define water of crystallisation.

Answer 19

Water molecules that are bonded to a crystal lattice e.g. NaCl.

Question 20

The solid salt containing WOC is …
Anhydrous substance has …

Answer 20

Hydrated.
No WOC.

Question 21

When blue crystals of hydrated copper sulphate are heated …

Answer 21

Bonds holding water together break and leaves anhydrous copper sulphate.

Question 22

Anhydrous copper sulphate may be pale blue because …

Answer 22

It’s hard to get rid of last traces of water.

Question 23

Experiment for water of crystallisation?

Answer 23

1. Weigh empty crucible, then reweigh with hydrated salt.
2. Use pipe clay triangle to support crucible on tripod. Heat contents.
3. Leave to cool then reweigh crucible and anhydrous salt.

Question 24

How long do you heat the contents for?

Answer 24

Crystals are heated repeatedly until mass of residue no longer changes, suggesting all water has been removed.

Question 25

Define empirical formula.

Answer 25

Simplest whole number ratio of atoms in a compound. Useful for giant structures.

Question 26

When finding empirical formula …

Answer 26

Find the ratio of moles.

Question 27

Define theoretical yield.

Answer 27

Maximum amount of product formed.

Question 28

Actual yield is always …

Answer 28

Less than theoretical/% yield never 100%.

Question 29

Why is this?

Answer 29

1. Loss of products on equipment e.g. filter paper.
2. Reaction is incomplete.
3. Unwanted side reactions.

Question 30

Percentage yield =

Answer 30

Actual/Theoretical x 100

Question 31

Atom economy measures …

Answer 31

How much reactant atoms become desired product.

Question 32

% atom economy =

Answer 32

RFM of desired product/RFM of all products all x100

Question 33

Atom economy if there’s only 1 product?

Answer 33

100% as all atoms are used up.

Question 34

Why is a higher atom economy better?

Answer 34

Reduces waste, preserves raw materials.

Question 35

What about lower atom economy?

Answer 35

More expensive as it costs more to dispose waste products safely.