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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?

A

temperature scale designed so that -273 degrees is 0 kelvins

23
Q

how to convert kelvins into degrees and back?

A

K = degrees + 273

degrees = K - 273

24
Q

what is the ideal gas law?

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
Q

ideal gas law rearranged to find the number of moles?

A

n = p v / R T

26
Q

ideal gas law rearranged to find the volume?

A

v = n R T / p

27
Q

how to change cm3 and dm3 into m3

A

cm 3 = x 10-6
dm3 = x 10-3

28
Q

Errors in titration and their effect
Leaving in a filter funnel

A

Could have liquid which drops into burette once you have started your titration
Effect: lowers final titre volume

29
Q

Errors in titration and their effect
Bubble under tap

A

Liquid must fill this space before being added to the conical flask
Effect: increases final titre volume

30
Q

Errors in titration and their effect
Ensure a conical flask is used

A

To ensure no loss of liquid whilst swirling

31
Q

Errors in titration and their effect
Not swirling constantly

A

Chemicals not fully mixed
Effect: increase in final titre volume

32
Q

Errors in titration and their effect
Not washing sides of conical flask just before end point

A

Due to splash back, reagents may be on one side of the flask and not in the mixture

33
Q

Percentage % uncertainty equation

A

Error value / quantity measured x 100

34
Q

If a weighing boat is measured and then re weighed later, how many error readings will there be?

A

2 error readings
Have to x 2

35
Q

How to find the overall error in your experiment

A

Add all the % errors together

36
Q

Brunettes error are:

A
  • 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
Q

What is the uncertainty of a 25cm3 pipette

A

+- 0.1cm3

38
Q

What is the uncertainty of a 25cm3 measuring cylinder

A

+- 0.5cm3

39
Q

what is the empirical formula

A

simplest whole number ratio of atoms of each element in a compound

40
Q

what is the molecular formula

A

actual number of atoms of each element in a compound

41
Q

hydrated compounds
4
5
7

A

tetrahydrate
pentahydrate
heptahydrate

42
Q

what is atom economy

A

measure of the proportion of reactant atoms that become part of the desired product in the balanced chemical reaction

43
Q

% atom economy

A

molecular mass of desired product/ sum of molecular masses of all reactants
x 100

44
Q

economic advantages of atom economy

A
  • efficient use of its raw materials
  • less waste products for a firm
45
Q

environmental/ethical advantages of atom economy

A
  • 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
Q

theoretical yield

A

mass of product that should be formed in a chemical reaction. it assumes no chemicals are lost in the process

47
Q

actual yield

A

the mass of the product actually formed through experiment
(yields may be given in moles or mass)

48
Q

theoretical yield equation

A

moles = mass (theoretical) / Mr

49
Q

percentage yield

A

actual yield / theoretical yield
x 100

50
Q

reasons for reduced yield

A
  • 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
Q

Why is a back titration used

A

Substances that are insoluble in water can’t be directly titration, am indirect method (back titration) is used

52
Q

% purity equation

A

Mass / mass of sample (stated in the Q) x 100

53
Q

Steps of back titrations

A
  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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