C4 - Stoichiometry
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Define relative atomic mass (Aᵣ) [1]
The average mass of naturally occuring atoms of an element on a scale where the ¹²C atom has a mass of exactly 12 units
Define relative molecular mass (Mᵣ) [1]
The sum of the relative atomic masses
What do the following state symbols stand for, s, l, g, aq? [4]
s = soild, l = liquid, g= gas, aq = aqueous
What is Avagadro’s number? [1]
6.02 x10²³
What is a mole? [1]
An amount of substance containing 6.02 x10²³ particles
What is the equation that relates number of moles, mass and relative atomic / molecular mass? [1]
number of moles = mass ÷ relative atomic / molecular mass
What is molar gas volume at RTP
The volume 1 mole of gas occupies at room temperature and pressure is 24 dm³
What is the equation that relates number of moles, volume and molar gas volume
number of moles = volume ÷ molar gas volume (24dm³ at RTP)
How many cm³ are there in 1 dm³? [1]
1000 cm³ = 1 dm³
How do you convert from cm³ to dm³? [1]
Divide by 1000
What are the units for concentration? [2]
g/dm³ or mol/dm3
What is the equation that relates number of moles, volume and concentration? [1]
number of moles = volume x concentration
What are the steps for calculating reacting masses? [5]
• Identify the two substances in the equation 2. Write n,m,M underneath each one and fill in what you know 3. Calculate the number of moles for one of the substances 4. Consider the stoichiometric ratios in the equation to calculate the number of moles of the other substance 5. Work out the mass / volume of the substance in question
What is a limiting reactant? [1]
The reactant that is used up first
What does it mean if a reactant is in excess [1]
There is more of it than needed to react with other reactant(s)