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AS Chemistry Unit 1 + 2 > Unit 1.3 - Chemical equations > Flashcards

Unit 1.3 - Chemical equations Flashcards

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1
Q

How many cm3 are in 1dm3?

What is 1 cm3 equal to?

A

1dm3 = 1000cm3

1 cm3 = 1 ml

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2
Q

How many mg are in 1g?

A

1g = 1000mg

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3
Q

How many g are in 1kg?

A

1kg = 1000g

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4
Q

How do you convert temperature to kelvin?

A

°C + 273

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5
Q

Relative isotopic mass

A

Mass of an atom of an isotope relative to 1/12th the mass of an atom of carbon - 12.

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6
Q

Relative atomic mass

A

Average mass of one atom of the element relative to 1/12th the mass of one atom of carbon - 12.

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7
Q

Relative formula mass

A

Sum of the relative atomic masses of all atoms present in its formula.

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8
Q

Relative molecular mass

A

Mr of an element is defined as the mass of one molecule divided by 1/12th the mass of one atom of carbon 12.

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9
Q

Mole

A

Mass of a substance that contains the same number of particles (atoms/molecules/ions) as there are atoms in 12g of the carbon-12 isotope.

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10
Q

Isotope

A

Atoms of the same element which have the same number of protons but a different number of neutrons.

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11
Q

Molecular ion

A

The positive ion formed in a mass spectrometer from the whole molecule.

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12
Q

Fragmentation

A

Splitting of molecules, in a mass spectrometer, into smaller parts.

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13
Q

Avogadro’s constant

A

Number of atoms per mole (same no. particles in 12g of C-12).

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14
Q

Stoichiometry

A

Molar relationship between the amounts of reactants and products in a chemical reaction.

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15
Q

Empirical formula

A

Simplest formula showing the simplest whole number ratio of the number of atoms of each element present.

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16
Q

Molecular formula

A

Shows actual number of atoms of each element present in the molecule.

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17
Q

Molar volume

A

Volume per mole of a gas. Only use if temp is between 0°C-25°C, pressure 1 atm.

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18
Q

Solute

A

Dissolved substance.

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19
Q

Solvent

A

Liquid in which the solute dissolves

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20
Q

Concentrated

A

Solution with large quantity of solute in a small quantity of solvent.

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21
Q

Error

A

Skilled worker would find difficult to avoid due to consequence of the way the apparatus has been constructed and how readings can be made using it.

22
Q

Mistake

A

Skilled operator can avoid by being careful.

23
Q

How do you calculate the number of moles?

A

n= m (g)/Mr

24
Q

How do you calculate the concentration?

A

C= n/V (dm-3)

25
Q

How do you calculate the number of moles in a given volume of gas at given temperature and pressure?

A

n= Vol./Molar Vol.

26
Q

How do you calculate the concentration in g dm-3?

A

Concentration (mol dm-3) x Mr

27
Q

Describe how to make a solution (5).

A

1) Accurately weigh the solute on a balance.
2) Dissolve the weighed mass in water in a beaker using a stirring rod.
3) Add to a volumetric flask washing through the beaker using a wash bottle.
4) Carefully add more water to the solution until it reaches the mark.
5) Mix the solution throughly by using a stopper and shaking it.

28
Q

Ideal Gas Equation

A

PV=nRT

29
Q

Ideal gas equation

1) What is pressure measured in?
2) What is volume measured in?
3) What is temperature measured in?
4) What does R stand for?

A

1) Pa
2) m3
3) K
4) Gas constant

30
Q

1) How many Pa are in 1kPa?

2) How may dm3 are in 1m3?

A

1) 1000Pa = 1kPa

2) 1000dm3 = 1m3

31
Q

How do you calculate the percentage yield?

A

actual yield/theoretical yield x 100

32
Q

How do you calculate atom economy?

A

theoretical mass of required product/total mass of reactants used x 100

33
Q

What are the 3 main steps in calculating reacting masses?

A

1) Work out number of moles (n= M/Mr)
2) Ratio of n:n
3) M= n x Mr

34
Q

What are the 3 main steps in titration calculations?

A

1) Work out number of moles (n= c x v)
2) Ratio of n:n
3) C = n/v

35
Q

What is back titration?

A

Amount of excess reactant unused at the end of a reaction is found and so the amount used can be calculated.

36
Q

What is the method for titration? (4)

A

1) Place an acid/alkali in a burette.
2) Measure 25cm3 of an acid/alkali using a pipette and place in a conical flask.
3) Add a few drops of indicator to the flask.
4) Titrate (add from burette) until there is a colour change.

37
Q

Why is atom economy important?

A

High atom economies produce less waste, which means more profit.

38
Q

How do you calculate the empirical formula?

A

Divide mass by atomic number, then divide by the lowest number.

39
Q

How do you calculate the molecular formula?

A

Actual Mr/Mr of empirical formula.

Multiply the formula by the calculated value.

40
Q

Mass spectrometry

1) What happens at vaporisation?

A

1) Elements are injected directly into the instrument just before the ionisation chamber. Less voliate solids must be preheated and vaporised.

41
Q

Mass spectrometry

2) What happens at ionisation?
2) Why will most of them carry a charge of +1?

A

2) Stream of vaporised element enters the ionisation chamber. Electrically heated metal coil gives off electrons which are attracted to the electron trap (positively charged plate). Particles become bombarded with a stream of electrons and some of collisions are energetic enough to knock electrons making positive ions.
2) More difficult to remove further electrons from an already positive ion.

42
Q

Mass spectrometry

3) What happens at acceleration phase?
3) What is the need for the vacuum?

A

3) Electric field accelerates the positive ions to high speeds.
3) Ions need to have a free run through the machine without hitting air molecules.

43
Q

Mass spectrometry

4) What does the amount of deflection depend on?

A

4) Mass of ion - lighter ions are deflected more than heavier ones
Charge of ion - Ions with 2 or more positive charges are deflected more.

44
Q

5) What happens at the detection stage?

A

Beams of ions passing through are detected via current. Only ions with the correct mass/charge ratio will make it through to the ion detector.

The other ions collide with the walls where they will pick up electrons and become neutralised.

45
Q

State 3 uses of mass spectrometry.

A

Identifying unknown compounds, identifying trace compounds in forensic science and analysing molecules in space.

46
Q

How do you calculate the relative atomic mass/abundance of an isotope?

A

Isotope number x length / all lengths added together

47
Q

Describe how the mass spectrum is formed (3)

A

Molecular ion forms from an electron being knocked off to give a positive ion.

They are energetically unstable and some will break into fragments.

Different fragmentations form causing a wide range of lines in the mass spectrum.

48
Q

What happens to chlorine when it is passed through the ionisation chamber?

A

Electron is knocked off cl2+ which undergoes fragmentation to cl+ which is more stable.

49
Q

How do you calculate percentage error?

A

% error = error/reading x 100

50
Q

State 3 sources of error in titrations.

A

Leaving funnel in burette, not reading the meniscus at eye level and over-shooting the end point.

AS Chemistry Unit 1 + 2 (6 decks)

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