2.1.3 Amount of Substances Flashcards
Definition of amount of substance
its the quantity that has moles as its unit. Chemist use ‘amount of substance’ as a way of counting atoms.
Define mole (symbol mol)
its the unit for amount of substances
Definition of Avogadro constant, na
the number of particles per mole
What is the Avagardo constant
6.02 X 10^23 mol^-1
Definition of molar mass
Its the mass per mole of a substance, units g mol^–1
Definition of molar gas volume
Its the volume per mole of a gas, units dm^3 mol^–1
Definition of Empirical Formula
Its the simplest whole number ratio of atoms of each element present in a compound
Definition of Molecular Formula
Its the number and type of atoms of each element in a molecule
What is one mole?
Its the amount of substances that contains 6.02 X 10^23 mol^-1 particles.
what is the triangle for moles from a mass?
Mass / moles X Mr
How do you find out the empirical formula?
- divide the amount of each element present by its molar mass
- divide the answer for each element by the smallest number
How do you find out the molecular mass?
- Add the relative atomic mass
- Mr / relative atomic mass
- answer to 2 x the compound
what is the triangle for moles from a gas volume in dm^3?
v / moles X 24.0
what is the triangle for moles from solution in dm^3?
moles / conc X volume
what is the triangle for moles from a gas volume in cm^3?
v / moles X 24’000
what is the triangle for moles from solution in cm^3?
moles / conc X (volume / 1000)
What is the ideal Gas equation?
pV = nRT
How do you find out the percentage yield?
- Calculate the amount, in mol, of product used
- Calculate the amount in mol, of expected product - by checking if the equation is a 1:1 ratio
- Find the actual amount, in mol, of product made
- Actual amount, in moles
———————————- X 100
Expected amount , in moles
How do you find out the atom economy?
molecular mass of the desired product
——————————————————— X 100
Sum of molecular masses of all product
Why is percentage yield more likely to be less than 100%?
> Reactant may not be pure
Seperation and Purification may result in loss of the product
Some reactant may be left behind in the apparatus used in the experiment
Side reaction may occur, leading to by-products
How does high atom economy benefit the society?
> Hight atom economy reduce the amount of waste produced
> Reactions with high atom economy make processes much more sustainable
