Amount Of Substance

Question 1

How to work out number of particles

Answer 1

Moles x avogadros

Question 2

How to find moles with mass and mr

Answer 2

Moles=mass/mr

Question 3

How to work out moles with concentration and volume

Answer 3

Moles = concentration (moles dm-3) x volume(dm3)

Question 4

What is the ideal gas equation and units

Answer 4

pV= nRT
pressure= Pa
Volume= metres cubed
Moles
R = gas constant
Temp = K

Question 5

How to work out empirical formular

Answer 5

1. mass/mr to find the moles
2. divide by smallest number

Question 6

How to work out molecular formula

Answer 6

1. Calculate the relative mass of an empirical formula
2. Divide relative formula mass by relative empirical mass
3. multiply

Question 7

charge of metals

Answer 7

positive

Question 8

charge of non metals

Answer 8

negative

Question 9

how to convert c to kelvin

Answer 9

add 273

Question 10

charge of ammonium

Answer 10

NH4 +

Question 11

charge of Hydroxide

Answer 11

OH-

Question 12

charge of Nitrate

Answer 12

NO3 -

Question 13

charge of Sulfate

Answer 13

SO4 2–

Question 14

charge of Carbonate

Answer 14

CO3 2–

Question 15

charge of Hydrogen carbonate

Answer 15

HCO3 –

Question 16

charge is Phosphate

Answer 16

PO4 3 –

Question 17

The water of crystallisation in calcium sulfate crystals can be
removed as water vapour by heating as shown in the following
equation.
CaSO4.xH2O(s) → CaSO4(s) + xH2O(g)
What is the method?

Answer 17

*Weigh an empty clean dry crucible and lid.
*Add 2g of hydrated calcium sulfate to the crucible and weigh again
*Heat strongly with a Bunsen for a couple of minutes
*Allow to cool
*Weigh the crucible and contents again
*Heat the crucible again and reweigh until you reach a constant mass (do this to ensure the reaction is complete).

Question 18

Why shouldn’t large amounts of hydrated calcium sulfate, such as 50g, should not be used in this experiment of water of crystallisation

Answer 18

the decomposition is
likely to be incomplete.

Question 19

Why does the crucible needs to be dry when doing the water of crystallisation

Answer 19

a wet crucible would give an inaccurate result. It would cause mass loss to be too large as the water would be lost when heating.

Question 20

Why do we use a lid when experimenting water of crystallisation

Answer 20

The lid improves the accuracy of the
experiment as it prevents loss of solid from the crucible but should be loose fitting to allow gas to escape

Question 21

atom economy formula

Answer 21

molecular mass of desired product/sum of molecular mass of all reactants x100

Question 22

what does percentage yield tell us

Answer 22

how wasteful a process is