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CHEMISTRY based on CGP > Section 1: Principles of Chemistry part2 > Flashcards

Section 1: Principles of Chemistry part2 Flashcards

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1
Q

what does aqueous mean?

A

dissolved in water

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2
Q

What is an isotope?

A

different atomic forms of the same element with the same no. of protons but different numbers of neutrons / atoms of the same element with diff. numbers of neutrons

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3
Q

How does one work out the relative atomic mass of an element taking into account isotopes and abundance? (3)

A
  1. Multiply the relative mass of each isotope by its relative abundance
  2. Add those together
  3. Divide by the sum of the relative abundances
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4
Q

Work out the relative atomic mass of chlorine:

Element: Chlorine R.M of isotope: a)35, b)37 Relative: abundance: a)3, b)1

A

Ar= [(35x3)+(37x1)] /(3+1) = 35.5

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5
Q

How does one find out the relative formula mass of a compound?

A

add together all the relative atomic masses of the atoms it contains

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6
Q

Ar of Mg=24 Ar of Cl=35.5
So…
What is the Mr of MgCl2???

A

24 + (35.5 x 2) = 95

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7
Q

What does the empirical formula give you?

A

the smallest whole number ratio of atoms in a compound e.g CH4 hast 1 C for every 4 Hs

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8
Q

Step-by-step method for calculating empirical formula?

A
  1. List all the elements in the compound
  2. Underneath them, write their experimental masses/percentages (what they give you in the question)
  3. Divide each mass/%age by the Ar for that particular element
  4. Divide each answer to step 3 by the smallest answer to step 3 that you got
  5. Get the ration in its simplest form: e.g by turning numbers which don’t come up as hole numbers into them
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9
Q

What does the molecular formula of a compound tell you?

A

The actual number of atoms of each element in a single molecule

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10
Q

How to find a molecule’s molecular formula given its relative molecular mass and its empirical formula?

NB: it isn’t absolutely vital that you learn these steps

A
  1. Find the mass of the empirical formula by multiplying the ratio of an element in the molecule by its RAM and then adding all of the values together
  2. Divide the relative molecular mass (given) by the mass of the empirical formula (which you just found). The answer is the no. of empirical units in the molecule.
  3. Thus, the molecular formula is the empirical formula multiplied by the empirical units
  4. Multiply each ratio in the molecule by the empirical units: you now have the molecular formula
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11
Q

Reacting masses: how would you work out the mass of magnesium oxide produced when 60g of magnesium is burnt in air?

Hint: find out the one you have info about and use ratios to find the unknown…

A
  1. Write out the balanced equation: 2Mg+O2=2MgO
  2. Work out the RFM of the 2Mg and the 2MgO you want to find the mass of, and multiply them by their respective rations in the balanced equation. 2Mg: 2x24=48 and 2MgO: 2x(24+16)=80
  3. We now know that 48g of Mg react to give 80g of MgO. Now, divide each no. of grams by 48 to find out the mass of MgO made from 1g of Mg. Then multiply these numbers by 60 to find the mass of MgO made from 60g of Mg. 1.67x60= 100g!!!!!!
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12
Q

percentage yield=

A

[actual yield(g) / theoretical yield(g)] x100

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13
Q

A mole is a number. What number is it?

A

6x10^23

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14
Q

If Carbon has an Ar of 12, what is the weight of one mole of Carbon?

A

12g

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15
Q

Diatomic Nitrogen has an Mr of 28, what is the weight of one mole of N2??

A

28g

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16
Q

Moles =

A

mass(g)/Mr

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17
Q

How many moles re there in 66g of carbon dioxide? Mr of CO2=44

A

66/44= 1.5moles

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18
Q

What does it mean if a solid salt is hydrated?

A

their lattices contain water molecules as well as positive and negative ions

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19
Q

what is the name given to the water in the lattices of hydrated salts?

A

water of crystallisation

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20
Q

If a salt doesn’t contain any water of crystallisation it is…

A

anhydrous

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21
Q

What is the hydrated formula of the salt MgSO4?

A

MgSO4.5H2O

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22
Q

How to work out the ratio of water needed to hydrate a specific salt? given the mass b4 and after dehydrating…

A
  1. Calculate the mass of both water and the compound
  2. Calculate number of moles of water lost using moles=mass/Mr
  3. Calculate the number of moles of anhydrous salt made
  4. Like you would with, empirical formula, divide each amount of moles by the smallest of these two values
  5. The answer= the unknown value of water!!!!! round it to a whole no. if it isn’t already
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23
Q

volume of gas (dm^3)=

A

moles of gas x 24

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24
Q

volume of gas (dm^3)= (in terms of Mr of gas…)

A

(mass of gas/Mr of gas) x 24

25
Q

1dm = how many cm?

A

1000

26
Q

unit for concentration? (2)

A

g/dm^3 OR mol/dm^3

27
Q

concentration=

A

moles / volume

28
Q

how to convert mol/dm^3 to g/dm^3

A

divide the mass of the chemical in grams by the volume of solvent used to dissolve it in in dm^3

29
Q

electric current is the flow of…

A

electrons/ions

30
Q

Why can ionic compounds only conduct electricity when molten or in solution?

A

the ions separate and are free to move in the solution, meaning they’ll carry electric current

31
Q

Do covalent compounds conduct electricity?

A

NO

32
Q

Why don’t covalent compounds conduct electricity?

A

Because they make bonds by sharing electrons, they don;t contain ions. This means they don’t have any charge carriers that are free to move, so can’t carry an electric current

33
Q

Define metallic bonding?

A

a giant structure of positie ions surrounded by a sea of delocalised electrons- the attraction between these cations and the electrons is called metallic bonding

34
Q

If electrons are delocalised, what does it mean?

A

they are free to move

35
Q

Give a property of a metal and say why?

A
  1. good conductors of heat and electricity; free electrons carry electrical current/heat energy through the mterial
  2. (mostly) malleable; the layers of atom can slide over each other
36
Q

What is an electrolyte?

A

a liquid that conducts electricity

37
Q

What is electrolysis?

A

Breaking down a substance using electricity

38
Q

In aqueous solutions which ions occur as well as the ions from the ionic compound? (2)

A
  1. hydrogen/H+ ions

2. hydroxide/OH- ions

39
Q

When will hydrogen gas be produced at the cathode?

A

If the metal ions are more reactive than the H+ ions

40
Q

If no halide ions are present, what will be formed at the anode?

A

oxygen

41
Q

How many coulombs in a faraday?

A

96000

42
Q

How many faradays in 1 mole of electrons?

A

1

43
Q

What mass of Na2O is produced when 50g of sodium is burnt in air?

A

124

44
Q

how to find the percentage yield of a reaction?

A

percentage yield = actual yield(g) / theoretical yield(g) x100

45
Q

what is the Avogadro constant and what does it represent?

A

6.023 x10^23 is the number of particles in a mole

46
Q

according to Avogadro’s Law, what volume does one mole of any gas occupy at room temp.?

A

24dm^3

47
Q

what does volume of gas n dm^3 equal? (when you know the moles of the gas)

A

moles of gas x 24

48
Q

how many cm^3 are there in 1dm^3

A

1000

49
Q

when you don’t know the moles of a gas, what is the equation used to work out the volume n dm^3?

A

volume(dm^3) = (mass of gas / Mr of gas) x24

50
Q

which ions will be present in an aqueous solution as well as the ions from the ionic compound?

A

H+ ions and OH- ions (hydrogen ions and hydroxide)

51
Q

what will be produced at the cathode during the electrolysis of an aqueous solution?

A

hydrogen gas, IF the metal ions are more reactive than the H+ ions

52
Q

what is produced in the electrolysis of an aqueous solution when the metal ions are less reactive than hydrogen?

A

a solid layer of the pure metal coating the cathode

53
Q

during the electrolysis of an aqueous solution in which halide ions are present, what will be formed at the anode?

A

molecules chlorine bromine or iodine depending on the halogen present will be formed

54
Q

during the electrolysis of an aqueous solution in which no halide ions are present, what will be formed at the anode?

A

oxygen

55
Q

which ions does a solution of sulphuric acid, H2SO4, contain?

A

SO42- , H+ , OH-

56
Q

what is the half equation for hydrogen accepting electrons at the cathode during electrolysis?

A

2H+ + 2e- –> H2

57
Q

during the electrolysis of sulphuric acid, which two things are produced at the anode and why? what is the half equation representing this?

A

because hydroxide ions lose electrons more easily than sulphate ions, oxygen and water are produced. 4OH- –> O2 + 2H2O + 4e-

58
Q

which 4 ions does a solution of sodium chloride contain?

A

Na+ , Cl- , OH- , H+

59
Q

in a solution to be electrolised containing both sulphate and hydroxide ions, which of these will go to the anode and why?

A

hydroxide ions because they lose electrons more easily

CHEMISTRY based on CGP (7 decks)

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