Chemistry 1.3 by Taylor keates https://padlet.com/taylorkeates/y4l6wtuaxd4 Made with charm en-us 2019-01-30 12:12:38 UTC 2023-04-09 03:08:31 UTC hello@padlet.com https://padlet-assets.s3.amazonaws.com/icons/Soccerball.png Percentage yield taylorkeates https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795544 percentage yield =
actual product ÷ predicted product x 100
Usually has numbers in the question.

Ethanoic acid & ethanol have a 1:1 ratio. If 32.1g of acid are produced from the oxidation of 27.6g of ethanol, what is the % yield?
obtained÷actual x100
Mr ethnoic acid - 60.04
Mr ethanol - 46.06
moles=mass÷Mr
27.6÷46.06= 0.6
1:1    0.6:0.6
mass = moles x Mr
0.6 x 60.04 = 36.024
32.1÷36.024 x 100 = 89%

]]> 2019-01-30 12:12:39 UTC https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795544 Titration calculations taylorkeates https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795547 Finding out the number of moles that will react together. Indicators are used to determine the end point in acid-based titrations. A burette measures a precise volume of liquid.

Eg. You have 50cm3 of NaOH(base) solution. Using methyl orange indicator you titrate the base against a 0.10moldm-3 solution of H2SO4. It takes 22.3cm3 of 0.10moldm-3 H2SO4 to neutralise 50.0cm3 of NaOH.
What is the conc. of NaOH solution?
Step 1: BALANCE EQUATION
2NaOH + H2SO4 --> Na2SO4 + 2H2O
Step 2: CONC. & VOL.
conc. acid - 0.10dm-3
vol. acid - 22.3cm3
conc. base - ?
vol. base - 50.0cm3
Step 3: RATIO
n=cv÷1000
0.10 x 22.3 ÷ 1000 = 2.23x10-3
2:1 NaOH:H2SO4
NaOH - 4.46x10-3
Step 4: CONCENTRATION
c=n x 1000 ÷ v
1000 x (4.46 x10-3) ÷ 50 =0.0892 moldm-3]]> 2019-01-30 12:12:39 UTC https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795547 Kelvin taylorkeates https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795550 To change celcius to kelvin..... add 273 to degree celcius]]> 2019-01-30 12:12:39 UTC https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795550 Ideal gas law taylorkeates https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795552               pV = nRT
p = pressure --> Pa or Nm-2
V = volume --> m3
n = moles 
R = gas constant 
T = temperature --> K]]> 2019-01-30 12:12:39 UTC https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795552 Concentration taylorkeates https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795554 The concentration measures how much of a substance is dissolved(solute) per unit volume of a solution(solvent).
Can be called molarity.
Measured in 2 ways:
molar conc. - moldm-3 or mass conc. - gdm-3

moles = concentration(moldm-3) x volume(cm3) ÷ 1000
n = cV÷1000]]> 2019-01-30 12:12:39 UTC https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795554 Stoichiometry taylorkeates https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795556 The mass of reactants and a balanced chemical equation means we can find the mass of the products.
Question. Fe2O3 is heated with carbon in a blast furnace. Fe2O3 reduced to Fe & CO is produced. I receive an order of 50kg of Fe.
How much Fe2O3 do I need?
Step 1: BALANCED EQ.
Fe2O3 + 3C --> 2Fe + 3CO
Step 2: RATIO
Fe2O3:Fe      1:2
Step 3: MASS --> MOLES
Fe Ar= 55.8 moles=mass÷Ar
kg-->g 50000g
50000÷55.8= 896mol Fe
Fe2O3 = 896÷2= 448mol
Step 4: MOLES-->MASS
mass=moles x Mr
448 x 159.6 = 71.5kg
Fe2O3=159.6]]> 2019-01-30 12:12:39 UTC https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795556 Gas volumes taylorkeates https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795558 We use the volume of mass per mole, molar volume(Vm) E.g at 0°C & atmospheric pressure(STP) we can say that Vm=22.4dm3 for any gas. This changes with temperature & pressure changes.
Volume of gas = moles x molar volume
V = M x Vm
Eg. 10g Zinc, reaction at STP, calculate hydrogen volume.
Zn + 2HCl --> H2 + ZnCl2
Zn:H2 = 1:1 ratio
V = M x 22.4         N=M÷Ar
N = 10÷65.4 = 0.153mol
V = 0.153 x 22.4 = 3.43dm3

]]> 2019-01-30 12:12:39 UTC https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795558 Empirical & molecular formulae taylorkeates https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795562 moles = mass ÷ Ar/Mr
The empirical formula is the simplest ratio.
Question. Find the empirical formula for the compound made of 75% C & 25% H.
moles= 75÷12= 6.25
moles= 25÷1.01= 24.7524
6.25÷6.25=1 24.7524÷6.25=4 *divide by smallest number*
                    1:4 compound - CH4
Question. 87.5% nitrogen & 12.5% hydrogen.
87.4÷14= 6.25     12.5÷1.01=12.4
6.25÷6.25=1        12.4÷6.25=1.98
                     1:2 NH2
 The Mr is 32.04.
Mr of NH2 = 16.02
NH2 --->(x2) N2H4]]> 2019-01-30 12:12:39 UTC https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795562 Mass spectra of Cl taylorkeates https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795564 Made up of 2 isotopes - 35Cl & 37Cl. The Chlorine35 isotope is three times more likely than the Chlorine37 isotope. ]]> 2019-01-30 12:12:39 UTC https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795564 Calculating relative atomic mass taylorkeates https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795566 *Assume 100 atoms*
QUESTION EXAMPLE:
A mass spectrum of a hydrogen sample showed it to contagion 1H 99.20% and 2H 0.8000%. 
Calculate the Ar of Hydrogen to 4sf.
(99.2 x 1) + (0.8000 x 2)
                    ÷
                100           = 1.008

]]> 2019-01-30 12:12:39 UTC https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795566 Mass spectrometer taylorkeates https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795569 It is used to find....
  • the mass of different isotopes of an element
  • relative abundance of each isotope of an element 
Ionisation
Vapour passes into the ionisation chamber. The particle sample is bombarded with a stream of electron & some collisions knock one(sometimes more) electrons to make positive ions.
Acceleration
an electric field accelerates the positive ions to a high speed.
Deflection
Different ions are deflected by a magnetic field by different amounts. Depends on....mass(lighter ions deflected more), charge on the ion(2+ are deflected more). These factors are combined into the mass/charge ratio
Detection
Beams of ions are detected electronically. Only ions with the right mass/charge ratio make it to the detector(other ions collide with the wall & pick up electrons becoming neutralised). These get removed by a vacuum pump. The signal often correct ions is amplified & recorded. 

Ions need a free run through the machine without hitting air molecules, so a vacuum is needed.
]]> 2019-01-30 12:12:39 UTC https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795569 Percentage error taylorkeates https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795571 Burette - 0.1cm3
0.2° thermometer - 0.2°
3-place scale - 0.001g/1mg
%error = error ÷ quantity measured x 100
quantity measured....titre(burette), Difference in temp(thermometer), mass(balance)
]]> 2019-01-30 12:12:39 UTC https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795571 Avogadro constant taylorkeates https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795573 6.02 x 1023 mol-1]]> 2019-01-30 12:12:39 UTC https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795573 Molar mass taylorkeates https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795575 amount in moles(n) = mass(m) ÷ molar mass(M)

E.g What is the amount of sodium present in 0.23g of sodium?
Ar=23.0
23.0 ÷ 23.0gmol-1 = 0.01mol]]> 2019-01-30 12:12:40 UTC https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795575 Atom economy taylorkeates https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795578 atom economy =
required product ÷ mass of  reactants x 100
Usually has a chemical equation in the question.

Calculate atom economy for making iron.
Fe2O3 + 3CO --> 2Fe + 3CO2
required÷total x 100
111.6 ÷ 243.6 x 100 = 45.8%]]> 2019-01-30 12:12:40 UTC https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795578 Solubility taylorkeates https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795579
  • Solute - what you're dissolving
  • Solvent - liquid
  • Solution- product
    • Often measure in g per 100g - g/100g
    The density of water is 1gcm-3

    Eg. Potassium nitrate has a solubility of 31.6g/100g water. Convert this to moldm-3
    Mr KNO3 - 101.1
    moles = mass ÷ mr
    31.6 ÷ 101.1 = 0.313
    0.313 x 10 = 3.13 moldm-3


    ]]>     2019-01-30 12:12:40 UTC https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795579     Gas constant taylorkeates https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795580 R = 8.31Jk-1mol-1]]> 2019-01-30 12:12:40 UTC https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795580 Mass Spectrometer taylorkeates https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795581 2019-01-30 12:12:40 UTC https://padlet.com/taylorkeates/y4l6wtuaxd4/wish/325795581