GCSE Chemistry C3 - Quantitative Chemistry

Law of Conservation of mass

• no atoms are lost or made during a chemical reaction so mass of products = mass of reactants

relative formula mass

sum of Mr of products

what does a base and acid make

salt and water

what does a metal and an acid produce

a salt and hydrogen gas

what does a carbonate and an acid make

a water, carbon dioxide and a salt

explain change in mass

• a gas is produced for example when a metal reacts with oxygen, metal oxide is produced which has a greater mass than the mass of the metal or when thermal decomposition occurs with metal carbonates and carbon dioxide is produce.

what is the purpose of cotton wool

stops the acid from spitting out

how to calc mol

n = m/M

how to calculate concentration

m = c x v

percentage yield

actual number / number you calculate x 100

why don't we make 100% of product

• reaction may not go to completion because it is reversable

• some of the product may be lost when it is seperated from the reaction mixture

• some of the reactants may react in ways different to the expected reaction

atom economy

a measure of the amount of starting materials that end up as useful products

percentage by mass

mr of element / total mr of the element x 100

how to calculate volume?

24 x moles

what is volume measured in

dm^3

Avogadro’s law

equal amounts of gases occupy the same volume under the same conditions of temperature and pressure

what is concentration measured in?

mol/dm^3

how do you get the concentration in grams?

concentration x mr

concentration (grams) unit

g/dm^3

concentration explaining

smaller vol or large mass of solute = higher conc
larger vol or smaller mass of solute = lower conc

why is atom economy useful

sustainable development and for the economic reasons to use reactions with high atom economy

possible reasons why a particcular reaction pathway is chosen/not chosen

atom economy, rate, usefulness of by-products, rate, yield, equilibrium position