Chapter 3: amount of substance

Mole

the amount of any substance that contains as many particles as there are C atoms in exactly 12g of the Carbon-12 isotope

How many particles in a mole?

6.02×10²³

molar mass

The mass per mole of substanc

stoichiometry

the ratio of the amount of substance (in mol) of each substance (given by balancing the chemical equation of a reaction)

molar volume

the volume per mole of gas (24dm³mol^-1)

room temperature & pressure

293K

101000Pa

equation linking volume and moles for a gas

mole=V/24

ideal gas equation

pV=nRT

assumptions made in ideal gas equation for molecules

random motion

Elastic collisions

Negligible size

No intermolecular forces

conversion from Celsius to kelvin

+273

atom economy

a measure of how well all atoms have been utilised

why is the percentage yield of a reaction never 100%?

Reaction may not go to completion

Side reactions may take place alongside main reaction

Purification of product may result in loss of some product

%yield formula

(actual yield/ theoretical yield) x100

sustainability benefits of a chemical reaction with high atom economy

large proportion of desired products & fewer waste products

Makes best use of natural resources

Makes industrial processes more efficient

atom economy formula

(molar mass of desired products/ molar mass of all products) x100

water of crystallisation

the water in a lattice

hydrated salt

a solid salt containing water of crystallisation

Anhydrous salt

a salt that doesn’t contain water

How to find the formula of a hydrated salt

calculate number of moles of water lost

Find number of moles of anhydrous salt

Find ratio oof moles of anhydrous salt to moles of water and insert into formula

why might experimental and theoretical values for the moles of water and anhydrous salt be different?

salt not heated to constant mass (not all water removed)

how to prevent experimental and theoretical values for the moles of water and anhydrous salt being different?

heat for longer

Use smaller mass

Heat until constant mass

standard solution

a solution of known concentration

how to make standard solution?

weigh solid

Dissolve solid in a beaker using less distilled water than will be needed to fill the volumetric flask to the mark

Transfer solution to volumetric flask

Rinse last traces of solution into flask using distilled water

Flask filled to graduation line using distilled water until bottom of meniscus touches line

Invert flask slowly several times to mix (not doing this makes titration results unlikely to be consistent)