Amount of Substance

Question 1

Relative Atomic Mass

Answer 1

Weighted average mass of an atom compared to 1/12th mass of a C-12 atom

Question 2

Relative molecular mass

Answer 2

Weighted average mass of a molecule compared to 1/12th mass of a C-12 atom

Question 3

Avogadro’s number

Answer 3

6 x 10^23 - number of entities in a mole

Question 4

Mole calculation for pure solids and gases

Answer 4

n = m/ Mr

Question 5

Mole calculation for gases

Answer 5

PV = nRT

Question 6

Units for gas mole equation

Answer 6

P = Pa
V = m^3
T = K

Question 7

Mole equation for solutions

Answer 7

n = cv

Question 8

Units for solution mole equation

Answer 8

V = dm^3
C = mol dm^-3

Question 9

Converting oC –> K

Answer 9

+ 273

Question 10

Converting cm^3 –> dm^3

Answer 10

/ 1000

Question 11

converting cm^3 –> m^3

Answer 11

/ 100 000

Question 12

converting dm^3 –> m^3

Answer 12

/ 1000

Question 13

Density equation

Answer 13

D (g cm^-3) = mass / volume

Question 14

Empirical Formula

Answer 14

Simplest whole number ratio of atoms of each element in a compound

Question 15

Method for empirical formula

Answer 15

Divide each mass of element by its Ar.
Divide through by the smallest number.
Find a whole number ratio without rounding

Question 16

Molecular Formula

Answer 16

Actual number of atoms of each element in a compound

Question 17

How to find Mr on a mass spectrometer

Answer 17

The furthest peak to the right is the molecular ion peak M+

Question 18

Turn concentration in g dm^-3 to mol dm^-3

Answer 18

g dm^-3 = mol dm^-3 x Mr

Question 19

% yield

Answer 19

= actual yield / theoretical yield x 100

Question 20

% atom economy

Answer 20

mass of useful products / mass of all reactants x 100

Question 21

Rule of 1 mole of gas at RTP

Answer 21

Will have a volume of 24 dm^3. n = V/24

Question 22

Method to make a standard solution

Answer 22

1. Weigh out required mass in weighing bottle.
2. Tip contents into a beaker and add enough water to dissolve.
3. Pour solution into a volumetric flask with a funnel.
4. Wash beaker, funnel and stirring rod with water.
5. Make solution up to the mark on flask.
6. Invert flask several times to mix solution.
7. Reweigh weighing bottle to calculate exact mass in flask.

Question 23

Titration method

Answer 23

1. Rinse burette and pipette with solutions to go into them.
2. Pipette one solution into conical flask.
3. Fill burette making sure jet space is filled.
4. Add a couple of drops of indicator to conical flask.
5. Mix solutions together swirling constantly and adding dropwise near end point.
6. Repeat titration until 2 concordant results within 0.1 of each other.
7. Record all titre values to 2 dp

Question 24

Calculating % error

Answer 24

apparatus error/ measurement made x 100

Question 25

Total % error

Answer 25

Add all equipment errors together

Question 26

How to decrease apparatus error

Answer 26

Use equipment with a greater resolution (more dp or graduands). Increase the size of measurements i.e. scale up expt.

Question 27

% difference between actual value and calculated value

Answer 27

(actual value - calculated value) / actual value x 100