P1- Quantitative chemistry Flashcards
How to work out relative atomic mass (Ar)
(Abundance X Mass) + (Abundance X Mass) divided by 100
How to work out relative formula mass (Mr)
(Number of element x It’s mass number) + (Number of element x It’s mass number)
How to calculate percentage by mass
Ar of the element divided by Mr of the compound x 100
What is conservation of mass
The total mass of the products formed in a reaction is equal of the total mass of the reactants
What is an uncertainty
An error within a measurement, every measurement made will have some uncertainty within it. The uncertainty in a result is +/- the smallest increment of a scale
What is a mole
A unit of amount of substance- one mole of a substance is the relative formula mass of that substance in grams
How to calculate the number of moles
Mass in grams (element or compound) divided by the relative formula mass (Mr)
How to calculate the number of atoms and molecules in a mole
Calculate the number of moles and multiply this by avogadro’s constant
What is avogradro’s constant
6.02 x 10^23
How to do mass calculations
Using the ratio step grid with ratio, mass, mr, moles and ratio step and your known and unknown mass
How to calculate concentration when involving solvents
moles of solute (g) divided by the volume of the solvent (dm3)
How to calculate concentration using mass
Mass divided by volume
What is concentration
The amount of substance (solute) dissolved in a certain volume of the solvent to create a solution. The unit used can be grams per dm3
How to convert from cm3 to dm3
divide by 1000 (x for dm3 to cm3)
How to convert from g/dm3 to mol/dm3
divide by the relative formula mass (Mr)
Why is it not always possible to obtain the full amount of product even though no atoms are gained or lost in a chemical reaction
The reaction may not go to completion because it is reversible, some of product may be lost when it is separated from the reaction mixture, some of reactants may react in ways different to the expected reaction
How to calculate percentage yield
Actual mass divided by theoretical mass x 100
Percentage yield table
Both compounds at the top and ratio, mass, mr and moles at the side of
What is atom economy
amount of starting materials that end up as useful products. it is important for reactions with high atom economy
First way to calculate atom economy
Ar(Mr) of desired products divided by the sum of Mr of all the reactants x 100
Second way to calculate atom economy
Ar(Mr) of desired products divided by the sum of Mr of all the products x 100
At room temperature and pressure (RTP) what will one mole of any gas occupy a volume of
24dm3
What is room temperature
20 degrees celsius
What is room pressure
1 atmosphere
