✨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

Ammonia + acid =

Answer 19

Ammonium salt.
NH3 + HCl = NH4Cl

Question 20

Metal carbonate decomposes (with heat) to

Answer 20

Metal oxide and carbon dioxide.
CaCO3 = CaO + CO2

Question 21

Define water of crystallisation.

Answer 21

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

Question 22

The solid salt containing WOC is …
Anhydrous substance has …

Answer 22

Hydrated.
No WOC.

Question 23

When blue crystals of hydrated copper sulphate are heated …

Answer 23

Bonds holding water together break and leaves anhydrous copper sulphate.

Question 24

Anhydrous copper sulphate may be pale blue because …

Answer 24

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

Question 25

Experiment for water of crystallisation?

Answer 25

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 26

How long do you heat the contents for?

Answer 26

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

Question 27

Define empirical formula.

Answer 27

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

Question 28

When finding empirical formula ...

Answer 28

Find the ratio of moles.

Question 29

Define theoretical yield.

Answer 29

Maximum amount of product formed.

Question 30

Actual yield is always ...

Answer 30

Less than theoretical/% yield never 100%.

Question 31

Why is this?

Answer 31

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

Question 32

Percentage yield =

Answer 32

Actual/Theoretical x 100

Question 33

Atom economy measures ...

Answer 33

How much reactant atoms become desired product.

Question 34

% atom economy =

Answer 34

RFM of desired product/RFM of all products all x100

Question 35

Atom economy if there's only 1 product?

Answer 35

100% as all atoms are used up.

Question 36

Why is a higher atom economy better?

Answer 36

Reduces waste, preserves raw materials.

Question 37

What about lower atom economy?

Answer 37

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