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Chemistry A Level > Atoms and Reactions > Flashcards

Atoms and Reactions Flashcards

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1
Q

How do you calculate rate of reaction?

A

Change in concentration / time

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2
Q

What effect does concentration have on rate of reaction?

A

Increased concentration gives more molecules in the same volume, this means that the molecules will be closer together so there will be a greater frequency of successful collisions

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3
Q

What is the effect of pressure on rate of reaction?

A

Increased pressure gives more molecules in the same volume, this means that molecules will be closer together so there will be a greater frequency of successful collisions (this is the same effect as when concentration is increased but pressure is for gaseous reactions only)

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4
Q

Effects of catalysts on rate of reaction?

A

Catalysts lower the activation energy that is required to start a reaction by providing an alternative route for the reaction to follow

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5
Q

What is the effect of surface area on rate of reaction?

A
  • When there is a greater surface area, there is a greater surface area to volume ratio
  • This means that more reactant particles are exposed at the surface
  • This leads to a greater frequency of successful collisions between reactant particles
  • This causes the rate of reaction to increase
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6
Q

What is one atmosphere of pressure in pascals?

A

101325 pascals

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7
Q

What is room temperature?

A

25ºC or 298K

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8
Q

What is the ideal gas law?

A

Pressure (pa) x volume (m^3) = number of moles (mol) x gas constant (8.314Jmol^-1K^-1) x temperature (K) The equation can also be written as (pV=nRT) - When rounding, everything should be rounded to 3sf or a more accurate value

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9
Q

Are organic acids strong or weak?

A

Organic acids are weak acids

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10
Q

Give 3 examples of strong acids

A

HCl, H2SO4 and HNO3

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11
Q

Give an example of a weak alkali?

A

Ammonia (NH4)

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12
Q

Give an example of a weak acid

A

CH3COOH (Ethanoic acid)

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13
Q

What determines a strong and weak acid?

A

Strong acids are fully ionised, meaning they fully dissociate into ions. Weak acids are only partially ionised, meaning not all their molecules dissociate into ions

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14
Q

What is an amphoteric substance?

A

A substance that can behave as both an acid and a base

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15
Q

What is a base?

A

A chemical that can react with acids and is a proton acceptor

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16
Q

What is concentration?

A

A measure of the amount of solute dissolved per unit of solvent

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17
Q

What is the strength of an acid determined by?

A

It’s determined by the acid’s chemical properties

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18
Q

What is concentration determined by?

A

The number of acid or alkali particles that you put into each cm^3

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19
Q

What is the equation to calculate the number of particles in a substance?

A

Number of particles = number of moles x Avogadro’s constant (6.022 x 10^23)

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20
Q

How do you work out the number of moles of a gas?

A

Moles of a gas = volume of gas (dm^3) / 24dm^3

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21
Q

What is the equation for concentration?

A

Concentration (mol or g/dm^3) = mass (or moles) / volume (dm^3)

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22
Q

What is a standard solution?

A

A solution of a known concentration

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23
Q

What is a concentrated solution?

A

A solution that has a large amount of solute per dm^3, a dilute solution has a low amount of solute per dm^3

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24
Q

What is the mass concentration of a solute?

A

The mass of solute dissolved in 1dm^3 of solution

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25
Q

How do you calculate percentage uncertainty?

A

(Error / measured value) x 100, you multiply your answer by 2 if you weigh something twice and by 3 if you weigh something 3 times etc.

26
Q

What is the main use of (NH4)2SO4?

A

It is used as a fertiliser

27
Q

Who developed the first idea of the atom?

A

The Greek philosopher Democritus

28
Q

(Early 1800s) What was Dalton’s atomic theory?

A
  • Atoms are tiny particles that make up elements
  • Atoms can’t be divided
  • All atoms of a given element are the same
  • Atoms of one element are different to those of every other element
29
Q

(1897-1906) What was JJ Thompson’s plumb pudding model?

A
  • Sea of positive charge
  • Negatively charged particles embedded in positively charged sea
  • The sea of positive charge is the pudding, the negatively charged particles are the plumbs
30
Q

(1909-11) What was Rutherford’s gold-leaf experiment?

A
  • He fired alpha particles towards a sheet of very thin gold
  • Some particles were deflected back towards the source of alpha particles
  • This suggested that the positive charge of an atom and most of its mass is concentrated in a nucleus at the centre and that negative electrons orbit this nucleus
31
Q

(1913) What was Bohr’s model?

A
  • Bohr altered Rutherford’s model so that electrons could only flow in certain paths
  • This helped to explain the energy of electrons at different distances from the nucleus
32
Q

What did Rutherford discover in 1918?

A

The proton

33
Q

(1923-1926) What did Schrodinger discover about electrons?

A

That they had wave like properties and introduced the idea of atomic orbitals

34
Q

What was discovered in 1932 by James Chadwick?

A

The neutron

35
Q

What is an isotope?

A

An isotope of an element has the same number of protons and electrons, the same mass but a different number of neutrons

36
Q

What is relative isotopic mass?

A

The mass of an atom of an isotope compared with one twelfth of the mass of an atom of carbon-12

37
Q

What is relative atomic mass?

A

The weighed mean mass of an atom of an element compared with one twelfth of the mass of an atom of carbon-12

38
Q

What is mass spectrometry?

A

A mass spectrometer is a piece of apparatus that can be used to:
- Identify an unknown compound
- Find the abundance of each isotope of an element
- Determine the structural information about molecules
A mass spectrometer determines the mass of a molecule or isotope by measuring the mass to charge ratio of ions

39
Q

How do you calculate the relative atomic mass of an element when you know the abundance of the different isotopes?

A

((isotopic mass x abundance) + (isotopic mass x abundance) etc.) / 100

40
Q

How do you calculate the moles of a substance?

A

Moles / molar mass

41
Q

How do you calculate the number of particles in a given amount of a substance?

A

Moles x 6.02 x 10^23

42
Q

How do you calculate the moles of a gas?

A

Volume of gas / molar gas volume (24000cm^3 or 24dm^3)

43
Q

What is empirical formula?

A

The simplest ratio of atoms of different elements in a compound

44
Q

What is molecular formula?

A

The number and type of atoms in a compound

45
Q

How do you calculate empirical formula?

A
  • Mass / formula mass = moles

- Moles / smallest moles, gives you ratios

46
Q

How can the ratio of salt to water in a hydrated salt be calculated?

A
  • You should way the hydrated salt before heating
  • You can heat the hydrated salt until the water molecules start to break away from the crystal structure, forming water vapour
  • Eventually, all the water molecules will be removed from the salt, this will leave an anhydrous salt
  • You should now weigh the anhydrous salt and subtract this from the initial mass which gives you the mass of water
  • You should now calculate the moles of anhydrous salt and the moles of water, you should divide the answers by the smallest answer to get in a ratio x:1 or 1:x
47
Q

How do you calculate percentage yield?

A
  • Actual amount of product (mol) / theoretical amount of product (mol)
  • You can determine the theoretical yield by writing an equation for the reaction
48
Q

How do you calculate atom economy?

A

Molecular mass of desired product / sum of molecular masses of all products

49
Q

Why is a 100% percentage yield very difficult to achieve?

A
  • The reaction may be reversible
  • By-products may be formed from unexpected reactions
  • Reactants or products may be left in apparatus during the experiment
  • Product may be lost during purification and separation
50
Q

Why are reactions with high atom economy important?

A
  • They make better use of finite resources

- Reduce the need to process and safely dispose of waste products

51
Q

In an ion what do the oxidation numbers add up to?

A

The charge of the ion

52
Q

What oxidation number does oxygen have in most of its compounds?

A

-2, it has different oxidation numbers when it’s in certain compounds such as peroxides, with fluorine and superoxides

53
Q

What oxidation number does hydrogen have?

A

+1 in all compounds except for metal halides where it has +1

54
Q

What oxidation number does chlorine have?

A

-1 in most compounds except or in compounds with fluorine and oxygen

55
Q

When an element’s oxidation number increases in a redox reaction, has the element been oxidised or reduced?

A

The element has been oxidised, the element has been reduced if its oxidation number decreases

56
Q

What is the oxidation number of iron in iron(III) chloride

A

3+, FeCl3, transition metals can have different oxidation numbers based on the compound they’re in, in iron(II) chloride the iron has an oxidation number of 2+

57
Q

What is the test for carbonate ions?

A

Add dilute nitric acid to a sample and pass any gas evolved through lime water. Carbonate ions are present if a white precipitate is formed in the lime water. CO3^2-(s) + 2H+(aq) → CO2(g) + H2O(l) , Ca(OH)2(aq) + CO2(g) → CaCO3(s) + H2O(l)

58
Q

What is the test for sulfate ions?

A
  • Make a solution of the sample
  • Add drops of barium nitrate solution
  • Positive result → white precipitate
  • Ba^2+(aq) + SO4^2- → BaSO4(s)
59
Q

What is the test for halide ions?

A
  • Make a solution of the sample
  • Add drops of silver nitrate solution
  • Positive result: white precipitate - chloride ions, cream precipitate - bromide ions, yellow precipitate - iodide ions
  • Confirm the result using ammonia, precipitate dissolves in concentrated ammonia
60
Q

What is the test for ammonium ions?

A
  • Add sodium hydroxide solution to sample
  • Warm the mixture
  • Test any gas evolved with damp red litmus paper, if the paper turns blue then ammonium ions are present
61
Q

Which order should the test for ions be carried out in?

A
  • Carbonate ions test
  • Sulfate ions test
  • Halide ions test
  • Ammonia ions test

Chemistry A Level (15 decks)

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