Calculations

Question 1

Equations to work out moles

Answer 1

Moles = mass/molar mass

Question 2

Equation for percentage yield

Answer 2

Percentage yield = (experimental yield/theoretical yield) x 100%

Question 3

How to work out RFM

Answer 3

HCl = 1+35.5 = 36.5

Question 4

How to work out RAM

Answer 4

Used to find out average atomic mass of isotopes using abundance
E.g
79Br = 53% , 81Br = 47%

(79x53) + (81x47)/ 100 = 80

Question 5

What is the empirical formula

Answer 5

Simplest formula

Question 6

How to find molecular formula

Answer 6

RFM molecular
——————— X empirical formula
FRM empirical

Question 7

Formula for concentration

Answer 7

Concentration = moles/volume in dm-3

To find dm, divide number by 1000

Question 8

What is Avogadro’s law of gases

Answer 8

1 mole of any gas occupies the same volume (24dm-3) at room temperature(25° C) and the same pressure (one atmosphere) -> RTP

Question 9

Equation including moles and volume

Answer 9

Volume in dm3
——————— = moles
24dm3

Question 10

What does 1 faraday equal

Answer 10

1 mole of electrons
96000 coulombs (charge)

Used in electrolysis

Question 11

What is titration used for

Answer 11

To work out how much acid is needed to react with an alkali solution to make a soluble salt

Question 12

What are the two types of concentration

Answer 12

• amount of substance (moles) per volume

- mass of substance per volume

Question 13

What is Redcat

Answer 13

Reduction at the cathode (gain electrons)