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chemistry > topic 5 > Flashcards

topic 5 Flashcards

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1
Q

what is a mole definition

A

measuring amount of substance

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2
Q

what number is a mole

A

avogadros number
6.02 x 10^23 atoms/molecules

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3
Q

how to work out number of particles

A

avogadros x moles

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4
Q

how to work out moles

A

mass / Me

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5
Q

cslculate the number of moles in 23g of gold

A

23/197
= 0.12 mol

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6
Q

how to work out moles in solution

A

conc. (moldm-3) x vol (dm3)

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7
Q

how to work out conc. in gdm-3

A

mass/vol

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8
Q

calculate moles of 200cm3 of 0.35 moldm-3 HCl

A

0.35 x 200x10-3
= 0.07 mol

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9
Q

what is empirical formula

A

simplest whole number ratio of elements in a compound

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10
Q

how to work out empirical formula

A
  1. write out elements involves
  2. write % as masses
  3. divide these by Mr to get moles
  4. divide all by smallest number of moles
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11
Q

work out empirical formula od a compound that contains 23.3% Mg, 30.7% S, 46% O

A
  1. Mg S O
  2. 23.3g 30.7g 46g
  3. 24.3 32.1 16
    = 0.96 0.96 2.88
  4. 1 1 3

MgSO3

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12
Q

work out the empirical formula when a hydrocarbin combusts completely to make 0.845g of CO2 and 0.173g H2O

A

1write H2O and CO2 headings
2. write doem masses
3. divide by Mr to get moles
4. divide number of C and H atoms by smallest moles

CO2 H2O
0.845g 0.173g
——— ———
44 18
=0.019 =0.0096x2=
0.0192
/ 0.019=1 /0.019=1

CH

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13
Q

how to work out molecular formula from empirical

A

work out Me of empirical/ Mr molecular
x atoms in empirical

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14
Q

what do ionic equations show

A

ions formed in solution and which particles are reacting

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15
Q

how to work out ionic equations

A

axe aq
ditich doubles

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16
Q

what is the ionic equation of H2SO4 + 2KOH –> K2SO4 + 2H2O

A

2H^+ + SO4^2- + 2K^+ + 2OH^- –> 2K^+ + SO4^2- + 2H2O

2H^+ + 2OH^- —> 2H2O

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17
Q

how to work out theoretical masses

A
  1. write equation and balance
  2. work out Mr and write as masses
  3. find 1 gram of compound you know the mass of x mass, divide other compound by this and x same
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18
Q

how much CaO can be made when 34g Ca burnt in O2

A
  1. 2Ca(s) + O2 (g) —> 2CaO (s)
  2. 40x2 = 80g 56x2 =112g
  3. /80=1g /80=1.4
    x34 = 34g x34 = 47.6g

= 47.6g

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19
Q

what is a displacement reaction

Study These Flashcards
A

more reactive element takes place of less reactive element in compound

20
Q

what is an acid base reaction

Study These Flashcards
A

form salt and water
carbonates produce carbon dioxide as well

21
Q

what is a precipitation reaction

Study These Flashcards
A

solid produced after 2aq reactants react

22
Q

how to work out moles from volume and molar gas volume

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A

volume/molar gas volume

23
Q

what is molar gas volume at room temperature and pressure

24
Q

what is molar gas volume at standard temperature and pressure

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A

22.4 dm3 mol-1

25
how much gas in cm3 is produced when 6.2g of Mg reacts with HCl at rtp
Mg(s) + 2HCl(aq) ---> MgCl2 (aq) + H2 (g) Mr Mg = 24.3 mol Mg = mass/Mr = 6.2/24.3 = 0.255 mol Mg:H2 1:1 ratio so H2 mol = 0.255 volume = mol x molar gas volume = 0.255 x 24 = 6.12 dm3 = 6120 cm3
26
calcualte amount of gas produced when 5.6 dm3 of N2O decomposes
N2O (g) ---> N2(g) + 0.5 O2(g) 1 mol N2O produces 1 mol N2 and 0.5 mol O2 1.5 mol produced overall 1.5x5.6 = 8.4 dm3
27
what is the ideal gas equation and all units
pV=nRT p- pressure (Pa) v- volume (m3) n- moles R - gas constant 8.31 JK-1mol-1 T - temperature (K)
28
how to convert m3 to dm3 to cm3
m3-->dm3 ' x1000 dm3-->cm3 x1000
29
what volume of H2 produced when 12g of K reacts with H2O at 100KPa and 298K, gas constant 8.31
2K(s) + 2H2O (l) --> 2KOH (aq) + H2(g) mass/ Mr 12/39= 0.31mol of K 2 moles K produces 1 mol H2 0.31/2=0.155 mol H2 v=nRT/p v = 0.155x8.31x298/100,000 = 3.84x10^-3 m3
30
what is a hazard
things that could cause harm
31
what is a risk
likelihood of harzard causing harm eg scalding from hot liquids burns from hot equipment burns from chemicals cuts from glass/metals
32
what is a risk assessment
identification of all hazards and risks associated likelihood of something going wrong seriousness of risk how to reduce risk
33
how to make a standard solution
weigh - weigh amount of solid precisely using balance and weighing boat transfer- transfer solid from weighing boat to beaker, wash any solid left into beaker using distilled water disolve- dissolve solid fully using distilled water, stir to ensure fully disolved transfer- transfer solution to volumetric flask using funnel, rinse beaker and glass rod into flask fill- use more distilled water to fill to graduation line, use pipette when near mix - invert flask to ensure solution fully mixed
34
what mass of solid NaOH is required to make 250c,3 of 0.75 mol dm-3 NaOH solution
work out moles conc. x vol 0.75 x 250x103 = 0.1875 mol use moles to calculate mass mol x Mr 0.1875 x 40 = 7.5g
35
how does a titration take place
have known acid or alkali in burette with known conc. have known volume of unknown acid or alkali conc. in conical flask add chemical in burette to conical flask until indicator changes read how much chemical was added to neutralise chemical in flask, read from bottom of meniscus
36
18.3 cm3 0.25 moldm-3 HCl required to neutralise 25cm3 KOH, calculate conc. KOH
1. write equation and balance HCl + KOh --> KCl + H20 2. calculate moles of HCl conc x vol 0.35 x 18.3x10-3 = 4.58 x10-3 mol 3. use equation to find molar ratio 1:1 HCl : KOH moles KOH = 4.58 x10-3 4. conc.= moles/vol 4.58x10-3 / 25x10-3 = 0.18 mol
37
what is an uncertainty
degree of error your measurements have hald the smallest increment on equipment if you are using more then one measurement with the same units you add uncertainties
38
how to calculate % uncertainty
uncertainty / reading x100
39
what are systematic errors
caused every time
40
what are random errors
caused through estimating readings vary
41
how to calculate % yeild
actual/theortical x 100
42
what is theoretical yield
amount of product produced assuming no products lost and all reactants fully react
43
how to calculate atom economy
Mr of desired product / sum of Mr of all reactants x100
44
what is atom economy
how efficient a reaction is
45
what is the importance of atom economy
- high atom economies produce less waste so benefit environment - high atom economies means that raw materials are used more efficiently, more sustainable - companies will try to use reactions that tend towards 100% atom economies - high atom economy means less by products so less time and money separating these from desirable product

chemistry (15 decks)

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