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Chemistry Year 12/13 > Module 2.1 - Atoms and Reactions > Flashcards

Module 2.1 - Atoms and Reactions Flashcards

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1
Q

What are the similarities and differences between isotopes of an element?

A
  • different masses
  • same number of protons and electrons
  • different number of neutrons in nucleus
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2
Q

Why are the reactions of isotopes of the same element the same?

A
  • isotopes have the same number and arrangement of electrons
  • neutrons make difference to chemical reactivity
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3
Q

What is 1u in kg?

A

1.66x10^-27kg

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4
Q

What is the relative isotopic mass the same as?

A

mass number for that element

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5
Q

What are the assumptions made when calculating the relative isotopic mass?

A
  • neglected the mass of the electrons

- protons and neutrons both weigh 1.0u

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6
Q

What does the contribution made by an isotope to overall mass depend on?

A
  • percentage abundance of the isotope

- relative mass of the isotope

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7
Q

What is meant by the term ‘relative isotopic mass’?

A

Mass of an atom of an isotope compared to one-twelfth of the mass of an atom of carbon-12

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8
Q

What is meant by the term ‘relative atomic mass (Ar)’?

A

The weighted mean mass of an atom of an element co mapped to one-twelfth of the mass of an atom of carbon-12

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9
Q

When is the relative formula mass used?

A

In giant structures i.e. ionic/giant covalent compounds, as uses simplest ratios go atoms in a structure

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10
Q

What can mass spectrometry be used for?

A
  • identify an unknown compound
  • find the relative abundance of each isotope of an element
  • determine structural information about molecules
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11
Q

What is Avogadro’s constant?

A

6.02x10^23 mol-1

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12
Q

What is meant by the term ‘a mole’?

A

The amount of any substance containing as many particles as there are carbon atoms in exactly 12g of the carbon-12 isotope

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13
Q

What volume does one mole of gas occupy?

A

24dm3

24000cm3

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14
Q

What is molar gas volume?

A
  • volume per mole of gas
  • units: dm3mol-1
  • RTP is 24dm3
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15
Q

How are gases assumed to behave?

A
  • continuous motion and don’t experience any intermolecular forces
  • exert pressure when they collide w each other and walls of their container
  • collisions between gas molecules and between gas molecules and the walls of their container are elastic - don’t cause KE to be lost
  • KE of gases increases w increasing temperature
  • gas molecules so small compared to container any difference in size of different gas molecules can be ignored
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16
Q

What is meant by the term ‘standard solution’?

A

A solution of known conc. Normally used in titrations to determine unknown info about another substance

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17
Q

How would you make up a standard solution?

A
  1. Use weigh by difference method to weigh out solute
  2. Completely dissolve solute in solvent in beaker. Transfer solution to flask and rinse beaker repeatedly, using more solvent, adding rinsing to flask
  3. Add solvent to flaks, but don’t fill all the way up yo graduation line
  4. Carefully add solvent drop by drop up to line on flask, until bottom of meniscus sits exactly on graduation mark on flask. If solution goes over meniscus line, must throw it away and start again
  5. Mix solution thoroughly, by inverting flask several times
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18
Q

How do you make a standard solution of known concentration?

A
  • know conc and volume of solution you need to make
  • work out amount, in mol, of solute needed
  • convert amount of solute into a mass, in g, so you know how much to weigh out
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19
Q

What does it mean if a solution is concentrated?

A

large amount of solute per dm3 e.g. concs greater than 10mol/dm3

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20
Q

What does it mean is a solution is dilute?

A

small amount of solute per dm3 e.g. normal bench solutions of 1-2 mol/dm3

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21
Q

How do you show giant structures in an equation?

A

empirical formula

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22
Q

How do you show elements in an equation when they have a giant structure?

A

shown by its symbol

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23
Q

What is meant by the term ‘stoichiometry’?

A

The molar relationship between the relative quantities of substances taking part in reaction

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24
Q

Why are yields of 100% rarely seem in practical work?

A
  • reactions may be in equilibrium and not go to completion
  • side reactions may occur leading to by products
  • reactants may not be pure
  • some of reactants/products may be left behind in apparatus used in experiment
  • separation and purification may result in loss of some product
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25
Q

What is the equation for percentage yield?

A

actual amount of product (mol)/theoretical amount of product (mol) x100

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26
Q

What is the equation for atom economy?

A

molecular mass of desired product/sum of molecular masses of all products x100

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27
Q

Why is a high atom economy important?

A

less waste, lots of money from companies for dealing w waste, high atom economy more sustainable and less waste of depleting resources

28
Q

What is the atom economy of an addition reaction?

A

100%

29
Q

What type of reactions have an atom economy less than 100%?

A

reactions involving elimination/substitution

30
Q

What is meant by the term ‘acid’?

A

A chemical that is a proton donor and releases H+ (aq) in solution

31
Q

What is the difference between a strong and a weak acid?

A
  • strong acids v good at giving up H+ (fully or nearly fully dissociate)
  • weak acids aren’t v good at giving up H+. When H+ released, quickly taken back. Only partially dissociate
32
Q

Give some examples of bases.

A
  • metal oxides
  • metal hydroxides
  • ammonia can act as a base
33
Q

What are some examples of common alkalis?

A
  • NaOH
  • KOH
  • NH3
34
Q

Compare the corrosiveness of acids and alkalis.

A

Alkalis more corrosive than acids

35
Q

What is the ionic equation of a neutralisation reactions?

A

H+(aq) + OH-(aq) –> H2O(l)

36
Q

Describe how ammonia acts as a base.

A
  • dissolves in water to form a weak alkaline solution
  • NH3(aq) + H2O(l) ⇌ NH4+(aq) + OH-(aq)
  • weak base as only small proportion of dissolved NH3 reacts w water (shown by ⇌)
37
Q

Give an example of a substance that is amphoteric.

A

amino acid - has carboxyl group (COOH) and amino basic group (NH2)

38
Q

What is meant by the term ‘amphoteric substance’?

A

Substance that can act as both an acid and a base

39
Q

Where do each of the ions of a salt come from?

A
  • cation usually from metal ion or ammonium ion
  • anion is derived from an acid
  • formula is same as parent acid but H+ replaced by cation
40
Q

What is a diprotic acid?

A

acid w 2 H+ ions

41
Q

What is an acid salt?

A

When a diprotic or polyprotic acid loses less H+ ions than it has to form an acid salt e.g. NaHSO4 sodium hydrogensulfate

42
Q

What is meant by the term ‘alkali’?

A

A chemical that reacts with an acid and is soluble in water releasing hydroxide ions (OH-)

43
Q

What is meant by the term ‘hydrated’?

A

Crystalline compound containing water molecules (water of crystallisation)

44
Q

What is mean by the term ‘anhydrous’?

A

Substance that contains no water molecules (water of crystallisation)

45
Q

How would you experimentally determine the structure of a hydrated compound?

A
  • weigh mass of hydrated salt
  • heat so water evaporates
  • weigh anhydrous salt
  • calculate moles of anhydrous salt and moles of water, molar ratio determines no. of water of crystallisation
46
Q

How do you carry out a titration?

A
  1. Using a pipette, add a measured vol of a solution to conical flask. Add suitable indicator
  2. Place other solution in burette
  3. Add solution in burette to solution in conical flask until reaction just been completed (end point). Measure vol of solution added from burette
47
Q

How can the methyl orange indicator be used in a titration?

A
  • in acid: red
  • in base: yellow
  • end point: orange
48
Q

How can the bromothymol blue indicator be used in a titration?

A
  • in acid: yellow
  • in base: blue
  • end point: green
49
Q

How can the phenophthalein indicator be used in a titration?

A
  • in acid: colourless
  • in base: pink
  • end point: pale pink (when base added from burette to aq acid. When acid added to base it goes colourless)
50
Q

What is the oxidation number of an uncombined element?

A

0

51
Q

What is the oxidation number of combined oxygen?

A

-2

52
Q

What is the oxidation number of combined oxygen in peroxides?

A

-1

53
Q

What is the oxidation number of combined hydrogen?

A

+1

54
Q

What is the oxidation number of combined hydrogen in metal hydrides?

A

-1

55
Q

What is the oxidation number of a simple ion?

A

charge on ion

56
Q

What is the oxidation number of combined fluorine?

A

-1

57
Q

What is the oxidation number of a compound?

A

0

58
Q

What does the (II) in iron(II) chloride represent?

A

the oxidation number of iron

59
Q

What is an oxyanion?

A

Negative ions that contain an element along w oxygen e.g. sulfate ions

60
Q

What is oxidation?

A
  • loss of electrons
  • gain of oxygen
  • increase in oxidation number
61
Q

What is reduction?

A
  • gain of electrons
  • loss of oxygen
  • decrease in oxidation number
62
Q

What is an oxidising agent?

A

A reagent that oxidises (takes electrons from) another species (itself becomes reduced)

63
Q

What is a reducing agent?

A

A reagent that reduces (adds electrons to) another species (itself becomes oxidised)

64
Q

What is ‘molar mass’?

A

Mass per mole, gmol-1

65
Q

What is meant by the term ‘empirical formula’?

A

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

66
Q

What is meant by the term ‘molecular formula’?

A

Shows the number and type of atoms of each element in the compound

Chemistry Year 12/13 (18 decks)

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