Amount of substance Flashcards
What is amount of substance?
Number of moles = n
Units = mol
What is Avagadros number
The number of things (atoms, molecules) in one mole of a substance. It is 6.02x10^23
What is molar gas volume?
The volume one mole of gas occupies at room temperature and pressure (24cm3)?
What is the equation for molar mass?
mass/amount. the unit is gmol-1 or g/mol
What is RTP
298K
101KPa
What is the ideal gas equation?
pV=nRT
Used to find the mol, volume or pressure (via rearragning) of a gas not at room temp and pressure.
p=pressure=Pa
V=volume=m3
n=mol
R=gas constant=8.
T=temp=K
What is room temperature and pressure?
298K (=273 to celsius)
101KPa
Convert 1m3 to dm3 then cm3
1m3 is 1000dm3 which is 1,000,000 cm3
What is an ideal vs real gas?
Ideal gases do not follow kinetic theory of gases;
moving very fast and randomly, having barely any volume, no intermolecular forces (they don’t repel r attract eachother), no KE is lost during collision and the gas temp is related to the average KE of the gas molecules.
Real gases follow the kinetic theory of gases.
Explain the ideal gas law
The volume an ideal gas occupies depends on its TEMP & PRESSURE.
Heater=moreKE=more frequent collisions with container wall.
To keep CONSTANT PRESSURE, molecules move further apart so VOLUME INCREASES.
So, volume is therefore directly proportional to the temperature (at constant pressure).
What is the gas constant for the ideal gas equation?
8.31JK-1mol-1
What is the equation for concentration of a solution?
Concentration (mol/dm3) = amount (mol)/volume(dm3)
How to calculate volumes of gases at room temperature?
Volume (dm3) = amount (mol)/24dm3
How to calculate empirical formula?
Divide the mass of each atom in the substance (g) by their atomic masses. Then divide by the smallest figure you get to get the ratio.
What is water of crystallisation/
Water molecules exisiting in crystal structures with a salt (hydrous). For every mole of salt is a number of moles of water; .XH20
How to use balanced equations to work out theoretical mass?
Write balanced equation
work out Ar or Mr of species involved and write as g.
Convert one side into 1g and multiply by the amount of g that reacts. Repeat to the other side for the answer.
How to find molecular formula from empirical formula?
Find the Mr of the empirical formula and divide by Mr of molecular formula. Multiply this with the number of atoms of each element in the empirical formula.
What is percentage yield?
Actual yield/theoretical yield x 100%
The theoretical yield is the amount produced assuming no product is lost and all reactants react fully.
What is atom economy?
Molecular Mass of desired products in a reaction/total molecular mass of all products x100%
It is a measure of a reaction’s efficiency.
List some reasons why 100% percentage yield is impossible?
Not all reactants reacted.
Impurities reacted with reactants forming other products.
Product lost (eg gas escapes) like when transferring from beaker to beaker.
Why is atom economy important?
- When high, raw materials used more efficiently, which is more sustainable.
2.Companies will tend to use reactions with 100% atom economy
3.High produces less waste, evironmentall good.
High = less by product so don’t need to spend money separating products
How to find mass of one molecule?
Divide the molecules Mr by avagadros constant.
Or find its no. mols by dividing the number of molecules by avagadros constant to find the moles. Then multiple by the Mr to find the mass.
