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Chemistry > 2.1.1, 2.1.2, 2.1.3 > Flashcards

2.1.1, 2.1.2, 2.1.3 Flashcards

Atomic structure and isotopes, formulae and equations, amount of substance

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1
Q

What is used to identify an element?

A

Atomic number

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2
Q

What is the relative mass of an electron?

A

1 / 1836

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3
Q

What letters represent mass and atomic number?

A

Mass = A
Atomic = Z

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4
Q

What is an isotope?

A

Atoms of the same element with different numbers of neutrons and different mass numbers but the same number of protons and electrons.

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5
Q

Why do different isotopes of an element react in the same way?

A

Same number of electrons, number of neutrons has no impact on reaction.

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6
Q

What is the mass defect?

A

The strong nuclear force holding together protons and neutrons causes a fraction of the isotope’s mass to be lost.

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7
Q

What is carbon-12?

A

The international standard for the measurement of atomic masses. 1 carbon-12 = 12u

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8
Q

What is relative isotopic mass?

A

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

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9
Q

What is relative atomic mass?

A

The weighted mean mass of an atom of an element relative to 1/12th of the mass of an atom of carbon-12.

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10
Q

What 2 things does the weighted mean mass take into account?

A

Percentage abundance and relative isotopic mass.

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11
Q

How are the percentage abundance of isotopes in a sample found?

A

Experimentally using a mass spectrometer.

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12
Q

Method of using a mass spectrometer to determine percentage abundance:

A
  1. A sample is placed in MS
  2. Vaporised and ionised to form cations.
  3. Ions are accelerated. Heavier ions separate from lighter as slower
  4. Ions are detected on mass spectrum as a m/z.
  5. The larger the abundance, the larger the signal
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13
Q

What 2 things can a mass spectrometer record?

A
  1. Percentage abundance of isotopes in a sample.
  2. Mass to charge ratios of isotopes.
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14
Q

What are binary compounds?

A

Contain two elements only e.g. H2O

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15
Q

What are polyatomic ions?

A

Atoms of more than one element bonded together e.g. NH4+

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16
Q

What is amount of substance, n?

A

Quantity used to count the number of particles in a substance in moles.

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17
Q

How many atoms are in 12g of carbon-12?

A

6.02 x 10^23

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18
Q

What is molar mass?

A

The mass per mole of a substance. Measured in g mol-1

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19
Q

What is a molecule?

A

Two or more atoms held together by covalent bonds.

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20
Q

What is molecular formula?

A

The number of atoms of each element in a molecule.

21
Q

What is empirical formula?

A

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

22
Q

Why is the empirical formula important?

A

Some substances don’t exist as molecules, so the empirical formula is useful for substances that form giant crystalline structures.

23
Q

What is relative molecular mass?

A

The weighted mean mass of a molecule with the mass of an atom of carbon-12.

24
Q

What is relative formula mass?

A

The mass of a formula unit compared with the mass of an atom of carbon-12.

25
Q

What is water of crystallisation?

A

Water molecules part of a crystalline structure.

26
Q

Method to determine the water of crystallisation in hydrated salts:

A
  1. weigh empty crucible.
  2. Add hydrated salt, reweigh.
  3. Use pipe clay triangle to support crucible on tripod.
  4. Heat gently for 1 min then strongly for 3 mins.
  5. Leave crucible to cool
  6. Weigh crucible and anhydrous salt.
27
Q

Assumptions when making an anhydrous salt:

A
  1. All water has been lost.
  2. Hasn’t begun to decompose after heating.
28
Q

What is concentration?

A

The amount of solute dissolved in 1dm3 of solution.

29
Q

What is a standard solution?

A

A solution of known concentration.

30
Q

How is a standard solution made?

A

Dissolving an exact mass of solute in a solvent and making up solution to an exact volume.

31
Q

What 2 things influence the volume of a gas?

A

Temperature and pressure.

32
Q

What is molar gas volume?

A

the volume per mole of gas molecules at stated temperature and pressure.

33
Q

What is RTP?

A

20’C and 101kPa / 1atm

34
Q

What is the molar gas volume at RTP?

A

24.0 dm^3 mol-1

35
Q

Equation linking amount, volume and molar gas volume:

A

n = V / Vm

36
Q

What is the ideal gas equation?

A

PV = nRT

37
Q

What is 0 Kelvin in Celsius?

A

-273’C

38
Q

What is the value of constant R?

A

8.314 J mol-1 K-1

39
Q

What are 2 key assumptions of the ideal gas equation?

A
  1. Forces between molecules are negligible.
  2. Gas molecules have negligible size compared to the size of their container.
40
Q

Method to find a relative molecular mass using the ideal gas equation:

A
  1. Add sample of volatile liquid to small syringe with a needle.
  2. Weigh syringe.
  3. Inject sample into gas syringe.
  4. Reweigh small syringe
  5. Place gas syringe in boiling water bath.
  6. Record pressure.
  7. pv=nrt to calculate unknown
  8. n=m/M to find molar mass
41
Q

How is the real gas equation different to the ideal gas equation?

A

Takes the volume of gas molecules and inter molecular forces into account.

42
Q

What is the stoichiometry of a reaction?

A

The ratio of the amount of each substance in a balanced equation.

43
Q

Method to identify an unknown metal:

A
  1. Attach gas syringe to conical flask.
  2. Weigh sample of metal and add to flask.
  3. Add excess HCl to the flask and replace bung.
  4. Measure max volume of gas in the syringe.
44
Q

What are 3 reasons to explain why it is difficult to achieve theoretical yield?

A
  1. Reaction may not go to completion.
  2. Side reactions.
  3. Purification may lose some mass.
45
Q

What is percentage yield?

A

The conversion of starting materials into desired product.

46
Q

What is atom economy?

A

A measure of how well atoms have been utilised.

47
Q

Benefits of improving atom economy:

A

Industrial processes are more efficient, preserves raw materials, reduces waste.

48
Q

What does the atom economy equation assume?

A

A 100% yield.

Chemistry (4 decks)

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