Formula mass and mole calculations Flashcards
How to calculating relative formula masses
To find the relative formula mass (Mr) of a compound, you add together the relative atomic mass values (Ar values) for all the atoms in its formula.
What is the mole?
Chemists measure the amount of a substance in a unit called ‘the mole’. This is a convenient way of counting atoms. It allows chemists to make predictions about the masses of different substances that are involved in reactions.
What is the Avogadro number?
One mole of atoms contains 6 x 1023 atoms, no matter what element it is. This is a very large number: it is 6 with 23 zeros after it. It is known as the Avogadro number.
What’s moles of elements?
One mole of carbon atoms has a mass of exactly 12 g. Because magnesium atoms each have twice the mass of carbon atoms (24Mg compared with 12C), one mole of magnesium has a mass of 24 g
What is moles of compounds?
A mole of a molecular compound contains 6 x 1023 molecules. It has a mass that is equal to its relative formula mass.
How to calculate a mole! ?
This equation shows how relative formula mass, number of moles and mass are related:
number of moles = mass ÷ relative formula mass
What is limestone made of?
Limestone is mainly calcium carbonate, CaCO3
How does limestone get broken down?
It is broken down to form calcium oxide and carbon dioxide when heated.
What is thermal decomposition?
Calcium carbonate breaks down when heated strongly. This reaction is called thermal decomposition.
Other metal carbonates decompose in the same way, including:
sodium carbonate
magnesium carbonate
copper carbonate
The equations for the thermal decomposition of copper carbonate
Copper carbonate -heat- Copper oxide + carbon dioxide
CuCO3 - heat- CuO + CO2
Metals high up in the reactivity series (such as sodium, calcium and magnesium) have carbonates that need a lot of energy to do what?
Decompose them. Indeed, not all the carbonates of group 1 metals decompose at the temperatures reached by a Bunsen burner.
