MODULE 2 - 2.1.2 and 2.1.3 compounds, formulae, equations, amount of a substance Flashcards
2.1.2 [compounds, formulae, equations] 2.1.3 [amount of a substance]
How are ions created?
Electrons and transferred from one atom to another to form compounds.
How to work out the formula of an ionic compound:
- Write ions e.g Ca2+ and NO3-
- Swap the charges to Ca- and NO3 2+
- Drop the charges to Ca and NO3 2
- Simplify to whole number ratio if needed to Ca(NO3)2
What are salts
Ionic compounds. Can be hydrated or anhydrous
How do you calculate water of crystallisation?
- Write out the 2 molecules involved
- Write their masses
- Divide the mass by the Mr to get n
- Divide the numbers by the smallest number of moles to get moles of water of crystallisation
What are ions that don’t get involved in a reaction
Spectator ions
How do you write an ionic equation?
Write out the number of ions then cancel any ions that appear on both sides of the equation for the simplest ionic equation
What is Avogadro’s number
1 mole = 6.02x10 (23) mol-1
How do you calculate the number of particles?
Number of particles = Avogadro’s number x number of moles
What is the mole equation for mass and mr?
number of moles = mass/mr
What is the mole equation for solutions?
Number of moles = concentration (moldm-3) x volume (dm3)
What is the mole equation for the ideal gas equation?
pV = nRT
What are the units for the ideal gas equation?
p= pressure (Pa) V= volume (m3) n= moles (mol) R= gas constant (8.31kJ mol-1) T= temperature (K)
What are the standard conditions?
298K and 100kPa
What is the empirical formula
The simplest whole number ratio of elements in a compound
How do you calculate percentage yield?
% yield = actual / theoretical x 100
Reasons for not obtaining the theoretical yield?
- Reaction has not gone to completion
- Side reactions
- Purification results in loss of product
What is a limiting reagent
The reactant that is not in excess and will be used up first
How do you calculate atom economy?
Atom economy = Mr of desired product / sum of Mr of all products x 100
What is the atom economy?
A measure of how well atoms have been utilised
What is the molecular formula?
The number and type of atoms of each element in a molecule
What are features of reactions with high atom economies?
- Produces a large proportion of desired products and less waste products
- Important for sustainability