Quantitative (formula, units and limiting reactant)

Avogadro constant

6\.02 x 10^23

formula for finding out mass

mass= moles x relative atomic formula

m=nMr

How to find the mass when concentration is given?

Mass = concentration (g/dm3) x volume (dm3)

dm3 to cm3

1 dm3 = 1000 cm3

Covert cm3 to dm3

divide by 1000

number of particles in a substance?

Moles x Avogadro’s number

Concentration (mol/dm3)

Moles / Volume (dm )

How to calculate the mass of the product when you are given the limiting reactant?

By using the mass of the limiting reactant and the balanced reaction equation.

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1. write out the balanced formula


2. Work out relative formula masses (Mr) of the reactants and products
3. Find out how many moles there is in the substance you want
4. Use the balanced equation to workout how many moles there will be of the other substance.
5. use the number of moles to calculate the mass

Why is one reactant always in excess?

To make sure all the other reactant is completely used up.

What is the limiting reactant?

The reactant which is completely used up is called the limiting reactant because it limits the amount of products.

Number of particles in a substance

Moles x Avogadro’s number

What is the conservation of mass?

no atoms are lost or made during a chemical reaction so the mass of the product is the mass of the reactants.

How do you calculate the percentage mass of an element from a compound ?

You calculate the RFM of the specific compound asked and divide it by the RFM of the whole element/reaction (whole side basically)