Amount of Substance (CDS)

Question 1

What is meant by relative atomic mass?

Answer 1

The average mass of an atom relative to the mass of 1/12 of the mass of an atom of C12

Question 2

What are the units for relative atomic mass?

Answer 2

g mol -1 or grams per mole

Question 3

What is an isotope?

Answer 3

An atom of an element that has the same amount of protons and electrons but a different neutron number

Question 4

Equation used to calculate the Ar from all the isotopes of an atom

Answer 4

(mass of isotope x abundance) / sum of abundances

Question 5

What is meant by relative molecular mass?

Answer 5

The mass of a molecule relative to 1/12 of the mass of an atom of C12

Question 6

What are the units for Mr?

Answer 6

g mol -1 or grams per mole

Question 7

How to calculate Mr

Answer 7

Sum of Ar values of all elements in the molecule

Question 8

What is meant by relative formula mass?

Answer 8

The mass of the formula, relative to 1/12 of the mass of an atom of C12

Question 9

What is the value of the mole?

Answer 9

6.02 x 10^23

Question 10

How much does 1 mole of C12 weigh?

Answer 10

12 grams

Question 11

How much does 0.5 moles of C12 weigh?

Answer 11

6 grams

Question 12

How much does 0.25 moles of C12 weigh?

Answer 12

3 grams

Question 13

How much does 5 moles of C12 weigh?

Answer 13

60 grams

Question 14

Equation the links the value of the mole, number of moles and number of atoms

Answer 14

Number of moles = number of atoms / 6.02 x 10^23

Question 15

Equation that links number of mols, mass and Mr

Answer 15

Mols = mass / Mr

Question 16

What is meant by x H20?

Answer 16

The amount of water relative to one mole of salt in a hydrated salt

Question 17

How to find xH2O

Answer 17

1. find the moles of anhydrous salt
2. find the moles of water
3. Divide by the smallest value to find the ratio

Question 18

What is the unit of concentration?

Answer 18

mol dm-3 or moles per dm3

Question 19

How many cm3 is 1dm3

Answer 19

1000 cm3

Question 20

Equation that links concentration, volume and moles

Answer 20

mols = conc x vol

Question 21

How to find the limiting reagent in a 1:1 ratio

Answer 21

1. Find out mols of each reactant
2. Lower value is the limiting reagent

Question 22

How to find the limiting reagent in a 1:2 ratio

Answer 22

1. Find out mols of each reactant
2. Multiply moles of the 1 reactant by 2
3. If vale of 2 reactant is lower it is the limiting reactant

Question 23

How much space does 1 mol of gas occupy at 1atm and 25 degrees celsius

Answer 23

24 dm3

Question 24

Equation that links 24, volume and moles in relation to gas

Answer 24

vol = mols x 24

Question 25

What is the ideal gas equation

Answer 25

PV = nRT

Question 26

What do the letter stand for in PV = nRT

Answer 26

P = Pressure
V = Volume in m3
n= number of moles
R = Gas constant
T = Temp in Kelvin

Question 27

What is the value of R (gas constant)

Answer 27

8.31 J . K-1 mol-1

Question 28

How to convert from m3 to cm3

Answer 28

x 10^6

Question 29

How to convert from cm3 to m3

Answer 29

x 10^-6

Question 30

How to convert from m3 to dm3

Answer 30

x 10^3

Question 31

How to convert from dm3 to m3

Answer 31

/ 1000

Question 32

Equation for % composition by mass

Answer 32

(molar mass of element in compound / Mr or RFM) x 100

Question 33

Steps to calculate empirical formula from mass of elements/ % composition

Answer 33

1. Divide mass or % comp by the Ar of the element
2. Divide by smallest value to get ratio

Question 34

Equation for % atom economy

Answer 34

(molar mass of desired product / molar mass of reactants) x 100

Question 35

Equation for % yield

Answer 35

(actual yield / theoretical yield) x 100