amount of substance

Question 1

The mole

Answer 1

The mole is the amount of substance in grams that has the same number of particles as there are atoms in 12 grams of carbon - 12

Question 2

Relative atomic mass

Answer 2

Is the average mass of one atom compared to one twelfth of the mass of one atom of carbon - 12

Question 3

relative molecular mass

Answer 3

Relative molecular mass is the average mass of a molecule compared to one twelfth of the mass of one atom of carbon - 12

Question 4

moles =

Answer 4

moles = mass/ Mr

Question 5

Pv =

Answer 5

Pv = nRT

Question 6

Concentration =

Answer 6

concentration = moles/volumes

Question 7

cm 3 — dm3

Answer 7

/1000

Question 8

cm3 — m3

Answer 8

/1000000

Question 9

dm3 — m3

Answer 9

/1000

Question 10

How to calculate molar mass

Answer 10

For a compound can be calculated by adding up the mass numbers of each element in the compound

Question 11

1000mg = g

Answer 11

1

Question 12

1000g = kg

Answer 12

1

Question 13

1000kg = tonne

Answer 13

1

Question 14

Avogadro’s constant

Answer 14

There are 6.022 X 1023 atoms in 12 grams of carbon - 12.
One mole of any specific entity contains 6.022 X 1023 of that entity

Question 15

No of particles =

Answer 15

No of particles = moles X Avogadro’s constant

Question 16

density =

Answer 16

density = mass/ volume

Question 17

empirical formula

Answer 17

An empirical formula is the simplest ratio of atoms of each element in the compound

Question 18

General method : empirical formula

Answer 18

1 - divide each mass (or % mass) by the atomic mass of the element
2 - for each of the answers from step 1 divide by the smallest one of those numbers
3 - sometimes the numbers calculated in step 2 will need to be multiplied to give whole numbers
4 - whole numbers = empirical formula

Question 19

Molecular formula

Answer 19

A molecular formula is the actual number of atoms of each element in the compound

Question 20

For the relative molecular mass

Answer 20

Work out how many times the mass of the empirical formula fits into the Mr

Question 21

The Mr of a substances can be found out from using the

Answer 21

mass spectrometer.
The molecular ion (the peak with highest m/z) will be equal to the Mr

Question 22

mass concentration =

Answer 22

mass concentration = mass/volume

Question 23

concentration - mol dm3 into g dm3

Answer 23

multiply by the Mr of the substance

Question 24

Ion dissociating

Answer 24

When soluble ionic solids dissolve in water they will dissociate into separate ions.
The ions can lead to the concentration of ions differing from the concentration of the solute

Question 25

diluting a solution will n

Answer 25

not change the amount of moles of solute present but increase the volume of solution and hence the concentration will lower

Question 26

moles = volume X concentration
if amount of moles does not change then -

Answer 26

original volume X original concentration = new diluted volume X original volume/new diluted volume

so..

new diluted concentration = original concentration X original volume/new diluted volume

Question 27

percentage yield =

Answer 27

actual yield /theoretical yield X 100

Question 28

Percentage atom economy =

Answer 28

mass of useful products / mass of all reactants X 100

Question 29

When do you not use balancing numbers

Answer 29

when calculating % atom economy