Formulae, Eqns And Amounts Of Substance

Question 1

Give the formula for all the different ions

Answer 1

Look on first page of notes

Question 2

What is an ionic equation?

Answer 2

One where the spectator ions are removed

Question 3

What is the Avogadros constant and what is it represented by?

Answer 3

6.02 x10^23

Represented by NA or L

Question 4

Give the 2 eqns for moles

Answer 4

Mass
Moles = ————
RFM

Moles (N) = c x v
———
1000

Question 5

Give the eqn for using the avogadros constant

Answer 5

Mass
——— = amount in moles
RFM

                               Number of particles  amount in moles =  —————————
                               NA(6.02x10^23)

Question 6

Calculate the mass of 100 zinc atoms

Answer 6

First get moles

Then get mass

Question 7

What is a limiting reactant

Answer 7

The reactant in a chemical reaction that limits the amount of product formed

Question 8

What is excess reactant

Answer 8

The reactant that remains when a reaction stops because all the limiting reactant has been used

Question 9

Iron(III) oxide can be reduced using solid carbon accounting to the eqn below

2Fe2O3 + 3C —> 4Fe + 3CO2

16g of Fe2O3 were placed in a crucible with 12g of carbon. Calculate the mass of iron formed.

Answer 9

From notes

Question 10

If a salt is hydrated what does that mean?

Answer 10

Contains water of crystallisation

Question 11

If a salt is anhydrous what does that mean?

Answer 11

Contains no water of crystallisation

Question 12

Write out the method of calculation

Answer 12

Mass of anhydrous salt and mass of water lost

Get moles of each

Divide each by moles of anhydrous salt

Value of H2O is degree of hydration