Chemistry Calculations

Question 1

What is Avogadro’s number?

Answer 1

6.02 x 10^23

Question 2

What is a mole?

Answer 2

1 mole = 6.02 x 10^23 particles/ atoms/ molecules
1 mole= relative mass in grams (e.g one mole of carbon is 12g of carbon)

Question 3

N=nxAv
NopamnomAv

Answer 3

Number of particles/ atoms/ molecules = number of moles x avogadros number
Rearrange for:
n=N/Av
Av=N/n

Question 4

m=nxMr
massnomrm

Answer 4

Mass (grams)= number of moles x relative mass (from periodic table)
Rearranged to:
n=m/Mr
Mr=m/n

Question 5

n=cxv
nomcov

Answer 5

Number of moles= concentration (mol/dm^3) x volume (dm^3)
Rearrange to get:
c=n/v
v=n/c
Just remember the units for conc are mol/dm^3 and you’re good

Question 6

v=nxVm
vnVm (car noise)

Answer 6

Volume (dm^3)= number of moles x molar volume (dm^3)
Rearrange to get:
n=v/Vm
Vm=n/v
I’m in me mums car, vnVm.

Question 7

m=cxv
macovo

Answer 7

mass (grams)= concentration (g/dm^3) x volume (dm^3)
Rearrange to get:
c=m/v
v=m/c
Again, just remember the units for concentration are g/dm^3 and it’s cool

Question 8

How many cm^3 are in one dm^3

Answer 8

1000cm^3 = 1dm^3

Question 9

How to calculate relative formula mass (Mr)

Answer 9

Step one: work out how many atoms of each element are in the chemical formula (count them up)

Step 2: add together the relative atomic mass values for all the atoms of each element

E.g Mr of CO2 = 12 + 16 + 16 = 44

Question 10

How to find relative formula mass (Mr) of an ionic compound

Answer 10

Use the empirical formula (simplest ratio of elements e.g C2O4 -> CO2) of the compound