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chemistry A - level > Mrs > Flashcards

Mrs Flashcards

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1
Q

Formulae for hydrochloric acid

A

HCL

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2
Q

Formulae for sulphuric acid

A

H2SO4

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3
Q

Formulae for nitric acid

A

HNO3

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4
Q

Formulae for ethanoic acid

A

CH3COOH

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5
Q

Formulae for ammonia (gas)

A

NH3

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6
Q

Formulae for carbon monoxide

A

CO

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7
Q

Formulae fro carbon dioxide (gas)

A

CO2

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8
Q

Formula for methane (gas)

A

CH4

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9
Q

Formulae for sulphur dioxide

A

SO2

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10
Q

What is the mass of an electron

A

1 / 1836
1 / 2000 th

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11
Q

What is the difference between the chemical properties of isotopes?

A

There aren’t any all isotopes are identical

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12
Q

Isotope calculation

A

( isotope mass x abundance ) + ( isotope mass x abundance ) / 100

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13
Q

how to make a standard solution?

A

1) weigh solution needed in a weighing boat
2) transfer solute in a glass beaker & rinse weighing boat with distilled water
3) swill solution, so solute is dissolved
4) pour solution into a volumetric flask
5) rinse the beaker and funnel, multiple times 2/3
6) place stopper on volumetric flask and shake
7) fill the flask up to the line with distilled water
8) invert & shake the flask

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14
Q

important points about standard solutions? the solute must:

A
  • be available in a very pure form
  • be stable over a long period of time
  • not decompose when dissolved in water
  • not absorb H20 or CO2
    -not be volatile
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15
Q

what is stoichiometry?

A

ratio between the number of moles of substances taking part in a reaction

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16
Q

standard solutions are always…

A

an exact amount

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17
Q

what are moles and gases relationship?

A

mole of any gas has the same volume under the same conditions of temperature and pressure.

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18
Q

moles and gases at room temperature?

A

at room temperature and pressure, a mole of gas takes up 24000cm3 (24dm3)

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19
Q

moles and gas equation

A

volume = moles x 24 ( or 24000)

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20
Q

what are the features of ideal gases?

A
  • particles have no volume
  • collisions are elastic
  • no interactions between particles
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21
Q

when do real gases behave like ideal gases?

A
  • at high temperatures
  • at low pressures
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22
Q

what are kelvins?

Study These Flashcards
A

temperature scale designed so that -273 degrees is 0 kelvins

23
Q

how to convert kelvins into degrees and back?

Study These Flashcards
A

K = degrees + 273

degrees = K - 273

24
Q

what is the ideal gas law?

Study These Flashcards
A

p v = n R T

p = pressure (pa)
v = volume (m3)
n = number of moles
R = constant, 8.31 JK-1mol
T = temperature (K)

25
ideal gas law rearranged to find the number of moles?
n = p v / R T
26
ideal gas law rearranged to find the volume?
v = n R T / p
27
how to change cm3 and dm3 into m3
cm 3 = x 10-6 dm3 = x 10-3
28
Errors in titration and their effect Leaving in a filter funnel
Could have liquid which drops into burette once you have started your titration Effect: lowers final titre volume
29
Errors in titration and their effect Bubble under tap
Liquid must fill this space before being added to the conical flask Effect: increases final titre volume
30
Errors in titration and their effect Ensure a conical flask is used
To ensure no loss of liquid whilst swirling
31
Errors in titration and their effect Not swirling constantly
Chemicals not fully mixed Effect: increase in final titre volume
32
Errors in titration and their effect Not washing sides of conical flask just before end point
Due to splash back, reagents may be on one side of the flask and not in the mixture
33
Percentage % uncertainty equation
Error value / quantity measured x 100
34
If a weighing boat is measured and then re weighed later, how many error readings will there be?
2 error readings Have to x 2
35
How to find the overall error in your experiment
Add all the % errors together
36
Brunettes error are:
- reading the burette at the start of this titration, half a division = +- 0.05cm3 - reading the burette at the end if the titration, half a division = +- 0.05cm3 - judging the end point to within one drop, volume of a drop = +- 0.05cm3 Total = +-0.15cm3
37
What is the uncertainty of a 25cm3 pipette
+- 0.1cm3
38
What is the uncertainty of a 25cm3 measuring cylinder
+- 0.5cm3
39
what is the empirical formula
simplest whole number ratio of atoms of each element in a compound
40
what is the molecular formula
actual number of atoms of each element in a compound
41
hydrated compounds 4 5 7
tetrahydrate pentahydrate heptahydrate
42
what is atom economy
measure of the proportion of reactant atoms that become part of the desired product in the balanced chemical reaction
43
% atom economy
molecular mass of desired product/ sum of molecular masses of all reactants x 100
44
economic advantages of atom economy
- efficient use of its raw materials - less waste products for a firm
45
environmental/ethical advantages of atom economy
- less raw materials, means less waste - limited supply is more efficient - less waste chemicals produced, which are often harmful to the environment - more sustainable - cheaper
46
theoretical yield
mass of product that should be formed in a chemical reaction. it assumes no chemicals are lost in the process
47
actual yield
the mass of the product actually formed through experiment (yields may be given in moles or mass)
48
theoretical yield equation
moles = mass (theoretical) / Mr
49
percentage yield
actual yield / theoretical yield x 100
50
reasons for reduced yield
- not all starting chemicals react fully - reaction's are reversible - loss of chemicals during transfers between containers or filter paper -other products are formed
51
Why is a back titration used
Substances that are insoluble in water can’t be directly titration, am indirect method (back titration) is used
52
% purity equation
Mass / mass of sample (stated in the Q) x 100
53
Steps of back titrations
1. Work out the moles of titre (T) 2. Use T to work out B2 3. Calculate Btotal 4. Minus B2 from Btotal to find B1 5. Use equation to work out moles of A from moles of B1 that reacted with it

chemistry A - level (16 decks)

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