Chemistry in society

• Calculate the mass of aluminium formed when 51 g of aluminium oxide Al2O3 are electrolysed


  step 1: formula mass for whole productsGFMofAl2O3= 102gstep 2:n = m/GFM-->51/102= 0.5 mol of Al2O3

  step 3: usemolar ratiofrombalanced equationto figure out aluminum moles2 Al2O3 (aq) ---> 4 Al (s) + 3 O2 (g)2 mol Al2O3 ---> 4 moles Al

  step 4:0.5moles Al2O3--> 0.5/2x4(moles Al)= 0.25 x 4=1 mole aluminium

  step 5:convert 1 mole into mass--> 55g of aluminum oxide will produce 27g of aluminum upon being electrolysed

  
• Relative formula mass

  The relative atomic mass of each element added
• No. of moles calculation

  1) find theRAM2)dividegramsof element byRAMi.e. Ne atoms in 160g on Neon = 160/20.2
• BOFCHIN

  Bromine

  Oxygen

  Fluorine

  Chlorine

  Hydrogen

  Iodine

  Nitrogen
• Calculate the no. of moles of:

  N2 molecules in14.0gof Nitrogen(bofchiN)1) RAM N2=28(14 x 2)2)14/28 = 0.50.5 mol -1
• Avogadro's number (NA)


  1 mol contains

  6.02 x 10^23
• Calculate the no. of moles of:

  Mg(OH)2 units in6.996gof Magnesium Hydroxide1) calculateRAM:Mg =24.30 x 2 =32H x 2 =2=58.3

  2)6.996/58.3 = 0.12

  0.12 mol -1
• calculate no of moles of:

  Na+ ions in189.15gof Sodium Sulphite, Na2S031) calculateRAM:Na x 2 =46S =32.1O x 3 =48=126.1

  2)189.15/126.1 = 1.5

  (2x Na ions)3)1.5 x 2= 3

  3 mol -1
• n

  number of moles
• C

  concentration (in moles per litre of solution)
• Vl

  volume of solution in litres

  (1L = 1000cm3)
• 1 litre in cm3

  1000cm3
• n =

  C x Vl
• Calculate the no. of moles of

  NaClunits in200mlof0.5 mol l-1sodium chloride solutionn= C x Vl1) 0.5 =C2) 200 =Vl3)0.5x200/1000

  0.1 molNaCl units
• Calculate no. of moles of Ca2+ ions in 100ml of 0.01 mol l-1 calcium hydroxide solution

  n = C x Vl1) 0.01 =C2) 100 =Vl3)0.01 x 100/1000

  0.001mol Ca2+ ions
• How to find the molar volume of a gas?

  1) find the mass of an evacuated flask (air removed) of known volume

  2) fill it to particular pressure with gas

  3) measure the new mass of the filled flask

  4) using the known V of the gas you can calculate the V of gas equivalent to the molar mass under the experimental conditions
• typical molar volume for

  gasatroom temp(ntpconditions)24l
• molar volume is variable dependent upon

  -pressure-temperatureof the gas
• STP (standard temperature and pressure)


  common standard for comparison of gases
• STP conditions

  273K/0°Cand1 atm= one mole gas occupies a V of22.4l
• calculating no. of moles (n) if

  solid or liquidmeasure its massn =m/GFM(in DB)
• calculating no. of moles (n) if

  solutionmeasure concentration and volumen = cVc in moles per litrev in litres(in DB)
• calculating no. of moles (n) if


  gas(molar volume equation)volume of gas/molar volumen = v/Vm(not in DB - memorise)
• What is

  molar volume?thevolume occupiedbyone moleof agas
• diatomic elements


  Br, O, F, Cl, H, I, Nx2forGFMcalculations
• design stage goal

  maximizeeconomic efficiency
• design stage considerations

  -availabilityof feedstocks-sustainabilityof feedstocks-sizeof yield- formation of side products that can berecycled, used, or sold for profit
• feedstock definition

  araw materialused to providereactantsfor an industrial reaction
• molar ratio: what does a balanced chemical equation do?


  used to show how thequantities of reactants relateto thequantities of productsin the reaction.