2.1.3 amount of subbstance

amount of substance

number of particles in a substance

Mole

Amount of a substance that contains as many elementary particles as there are atoms in exactly 12g of carbon 12

what is amount of substance measured in

moled

what is avogradro constant

number of particles per mole

avogadro constant number

6.02 × 10²3

how to find out number of moles from number of atoms or moelcules

number of moles=number of particles u have/number of particles in a mole

hpw to work out number of atoms from moles

times moles by avogadros constant then times by how many atoms there are

how to calculate number of particles

moles x avogadro constant

moles equation,mass,mr

moles=mass/mr

moles concentration volume equation

moles=concentration x volume

molar mass

mass per mole

molar mass units

g mol^-1

molar gas volume

gas volume per mole

molar gas volume unit

dm³ mol^-1

empirical formulae

simplest whole number ratio of atoms of each element present in a compound

molecular formulae

actual number of atoms of each type of element in a molecule

molecular formulae equation

multiplier= Mr of molecule/empirical Mr

how to calculate empirical formulae from experimental data

• work out how many moles of each product has been made using moles=mass/mr

• use moles of each product made to work out how many moles of each atom you stater with

• then write down ratio of moles present at the start

• divide by the smallest number of moles to get whole number ratio

How to calculate empirical formulae from experimental data where your told one product and reactant

Mass of reactant a=mass of product-mass of reactant b

how to calculate empirical formulas from percentage compositions

• assume youve got 100g of the compound-turn percentages straight into masses then you can work out how many moles of each element are in 100g of the compound

• divide each number of moles by the smallest number of moles you founf in step 1 giving you the ratio of the elements in the compound

• apply numbers from ratio to formula

how to calculate molecular formula

• dividing molar mass by mass of empirical formula tells you what factor you need to scale the empirical formula up by to get molecular formula

water of crystallisation

water that is part of the crystalline structyre the molecules are stoichiometrically chemically bonded into the crystal structure

anhydrous substance

contain no water of crystallisation

hydrated substance

contains water of crystallusation

how to work out formula of hydrated salt

• first find mass of water lost by taking the mass of the anhydrous salt away from the mass of the hydrated salt

• then find number of moles of water lost

• find number of moles of anhydrous salt thats produced

• work out ratio of moles of anhydrous salt to moles of water

• scale up or down so that your ratio is in form 1:n,round of answer

what do uput between hydrates salt

dot between water and other molecule

how to solve reacting masses

1. qrite out balanced equation

2. work out moles by dividing mass by mr

3. use molar ratio to work out number of moles of product

4. now find mass of product by timesing by mr

percentage yield

actual/theoretical yield x 100

How to calculate theoretical yield

1. Work out number of moles of Limiting reactant

2. Use equation to work how many moles of products you would expect that much reactant to make

3. Calculate the mass of that many moles of product

why is % yield less than 100

• reversible reaction

• unexpected products

• left behing in apparatus

• reactants nnot pur

atom economy equation

mr of desired product/mr of reactants x 100

importance of high atom economy

• minimise watse of non renewable resources

• mske as much usefuk products

• reduce pollution

• minimise energy

• reduce use of water

what measures mass

balance

important with balance

suitable resolution

what used to measure volume of solution

measuring cylinderor volumetric flask

what to use to measue volune of gas

gas syringer or measure mass lost on balance

what are standard conditions

• 0C/273K

• 100kpa

how many volumes of gas does 1 mole of gas occupy underr standard constions

22.7dm³

normal lab conditions

• 25C/298K

• 100Kpa

how many volumes of gas does 1 mole of gas occupy underr lab conditons-room

24 dm³

kelvin in C

K=c+273

1dm³ in cm³

1000

moles of gas and volume at rtp equation

no of moles=volume in dm³/24

ideal gas equation

• PV=nRT

• pressure x volume=number of moles x constant x temperature

unit of volume in ideal gas equation

m³

unit of pressure in ideal gas eqaution

pa

unit of temperature in ideal ggas equation

K

1m³ in cm³

1,000,000

1m³ in dm³

1000

1KPa in Pa

1,0000

ideal gas cosntant

8.31 JK^-1mol^-1

concentration and volume equation

number of moles=concentration x volume(dm³)