TOPIC 5 - FORMULA, EQ AND AMOUNTS OF SUBST

The number of atoms, molecules or ions in one mole of a substance. 6.02 x 10^23 particles per mole

measures the amount of substance. DEF - 1 mole of any substance contains the same no. of particles as no. of atoms.

The mass of one mole of a chemical with the unit g mol-1. n = m / M

= no of moles * Avogrado’s constant

• Most inorganic reactions. so. .. 1. total combined mass of reactants = total combined mass of products –> LAW OF CONSERVATION 2. RATIO of species corresponds to the no. of moles

• Some organic reactions so. .. 1. ASSUME EVERYTHING IS 1:1 RATIO • USE LIMITING REACTANT AS 1:1 RATIO BY CALC MOLES TO FIND PRODUCTS MOLES AND REMEMBER Cl2 IS Mr Times by 2 • used to calc % YIELD

= product formed / theoretical product formed * 100 both in grams • indicates how efficient a reaction is at converting reactants to products

• may have reversible reactions • some products may be lost when separated from reaction mixture. • some reactants may react in other reactions

of a reaction is % of the total mass of reactants that can in theory be converted into the desired products. = mass (n*Mr) of desired products/ total mass of products * 100

• how to make a particular useful product - aware of environmental concerns abt processing and disposing waste

• high A.E, less waste, more efficient product process and preserves raw materials

The simplest whole number ratio of the atoms of different elements in a compound

• Write down the actual mass or percentage of each element • Write down the molar mass of each element • Divide the actual mass by the molar mass for each element • Divide all the numbers by the smallest one • See ratio to find % of each element in compound then times by 100 of Mr(C/H/O) / Mr of compound

The total number of atoms of each element in the molecule

• Find the molar mass of the empirical formula and divide by relative molecular mass of compound and that no. times by empirical formula

• Find the molar mass of the empirical formula and divide by relative molecular m ass of compound and that no. times by empirical formula

pV = nRT 1 atmosphere = 100,000 Pa 1 bar = 100k Pa (100,000Pa) To convert °C into K... +273 to the number 1m^3 = 1000dm^3 (1,000,000cm^3) R= 8.314 JK-1mol-1

m(H20) = 12.30 -6.0 =6.3g n(H20) = 6.3/18 = 0.35 mol N(MgSO4) = 6/120.4 = 0.050 mol MgSO4 : H20 0.050/0.050 : 0.35/0.050 1 : 7 Mr [MgSO4. 7H2O] = 246.4g

mass of pure/ mass of impure * 100

metal salt + hydrogen REDOX REACTION - metals below H in reactivity series do not react - TEST FOR H2: SQUEAKY POP TEST light splint and sound heard confirms hydrogen present.

metal salt + water metal salt + water • insoluble bases form precipitate metal salt + water + carbon dioxide TEST CO2: LIMEWATER TURNS CLOUDY AND PRECIPITATE PROD - limestone and water react –> limewater and co2 thermal decomp reverse Ammonium nitrate/chloride/sulfate test : damp red litmus paper turns blue. ALL ARE NEUTRALISATION REACTIONS Acids are PROTON DONORS Alkaline are PROTON ACCEPTORS

red - purple - blue colourless - pale pink - bright pink red - orange - yellow

= m/v divide by 1000 if cm3 to dm3

n(Na2co3) = 5.3/106.0 = 0.05 moles n(Na2CO3.nH20) = 0.05 Mr (Na2CO3.nH20) = 6.2/0.05 = 124.0 Mr( nH20) = 124.0 - 18.0 n = 18/18 = 1 ALWAYS 3 SIGFIG ON PAPER XS(ACID) - UNREACTED ACID = REACTED ACID