What is RFM?
Relative formula mass (sum of all the Relative Atomic Masses of atoms in a compound)
Are big numbers (coefficients) used in RFM?
No
Moles =
Mass/RFM
what are moles?
Moles are a way of measuring the amount of an element based on weight (e.g: 12g of carbon = 1 mole of carbon = 602000000000000000000000 atoms)
Mass =
moles x RFM
What is Avogadro’s constant?
6.02 x 10^23
How do you calculate the number of atoms in a mole of a compound?
- Find the number of atoms in the compound (e.g: for H2O it would be 3)
- Multiply this number by Avogadro’s constant (6.02 x 10^23)
How do you calculate the number of atoms in a given mass of an element?
- Find the number of moles
- Multiply this number by Avogadro’s constant (6.02 x 10^23)
How do you calculate the number of atoms in a given mass of a compound?
- Find the number of moles
- Multiply this by the number of atoms in the compound
- Multiply this number by Avogadro’s constant (6.02 x 10^23)
How do you balance an equation given masses and RFM of elements and/or compounds?
- Find all the moles
- Divide by the smallest number of moles to get the ratio
- Use these numbers as coefficients to the elements and/or compounds to balance
How do you solve a reacting masses question?
- Find the ratio of the elements and/or compounds in the equation (the coefficients)
- Find the moles of the element or compound that you have been given the mass for
- Apply the ratio to this number (e.g: if the moles are 2 and the ratio is 1:2, you end up with 4 moles)
- Multiply this number of moles by the RFM to get the mass of the desired element/compound
How do you solve a limiting reactant question?
- Find the ratio of the elements and/or compounds in the equation (the coefficients)
- Find the moles of all elements/compounds
- Apply the ratio to the moles
- Whichever element/compound that does not meet the ratio is the limiting reactant
What is the unit of concentration?
g/dm^3
concentration =
mass/volume
How do you convert dm^3 to cm^3
1dm^3 = 1000cm^3
