Calculations

Front 1

Moles

Back 1

Moles = Mass(g)/Molar Mass (gmol^-1)

Front 2

Relative atomic mass (Ar)

Back 2

The weighted average mass of naturally occuring atoms of an element on a scale where C-12 has a mass of exactly 12 units

Front 3

Relative Molecular mass (Mr)/ formula mass

Back 3

The mass of a molecule on a scale where the C-12 isotope has a mass of 12 units.

Front 4

Ar from Mass spectra (% abundance)

Back 4

Multiply each isotopic no. by the % abundance

Add figures together

Divide by 100

Front 5

Reacting Masses

Back 5

Find the moles,

Then look at the ratio

Then find the mass

Front 6

% composition

Back 6

(Ar of all that element in molecule/ Mr) *100

Front 7

Empirical formulae (definition)

Back 7

The simplest whole number ratio of elements present in a molecule.

Front 8

How to find the Empirical Formula?

Back 8

1)mass or % ÷ ar (for all elements in molecule)

2)divide by smallest to find ratio

3)apply this to elements

Front 9

Molecular formulae

Back 9

1) Find the mass of the empirical formula

2) divide the given mass by the empirical formula mass

3) multiply the empirical formula ratio by the previously calculated number.

Front 10

Ionic Equations

Back 10

1) Write the full balanced equation

2) write it out again with all the ions present

3) cancel out the spectator ions

4) write the final ionic equation

Front 11

Concentration (moldm^-3)

Back 11

= moles/vol(dm^3)

Front 12

Calculating conc in titrations

Back 12

1) find the moles of the acid

2) ratio

3) calculate the conc from this (given vol)

Front 13

Volume (for gases)

Back 13

= Mr * moles