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Chemistry OCR A > Module 2: Foundations in Chemistry > Flashcards

Module 2: Foundations in Chemistry Flashcards

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1
Q

Define relative molecular mass.

A

The mass of that specific molecule, relative to the mass of 1/12 of a carbon-12 atom.

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2
Q

Define relative atomic mass.

A

The weighted average mass of an atom of an element taking into account all of its naturally occurring isotopes relative to the mass of 1/12 of a carbon atom.

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3
Q

Why is the mass of an atom not proton+neutron+electron?

A

Due to the strong nuclear force holding protons and neutrons together, some mass is lost, and this is called mass defect.

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4
Q

Why are the radii of two isotopes of the same element the same?

A

They have the same number of protons and electrons.

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5
Q

What is the empirical formula of a compound?

A

The simplest whole number ratio of atoms present in a molecule of a compound.

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6
Q

What is the ideal gas equation?

A

PV=nRT

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7
Q

Define oxidation number.

A

The number of electrons involved in bonding an element to another.

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8
Q

What is the oxidation number of an element?

A

0

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9
Q

When is a reaction classified as redox?

A

In terms of electrons: Electrons are lost and gained

In terms of oxidation numbers: Oxidation numbers increase and decrease

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10
Q

What are the oxidation number exceptions?

A
  • Hydrogen in metal hydrides: -1
  • Oxygen in peroxides: -1
  • Oxygen when bonded to fluorine: +2
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11
Q

Define disproportionation.

A

When a single element is both oxidised and reduced in a reaction.

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12
Q

How many electrons does an orbital hold?

A

Two, which spin in opposite directions.

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13
Q

What are the exceptions when writing electron configuration?

A
  1. 4s is filled before 3d, because it has less energy, however it also loses electrons before 3d.
  2. For chromium and copper, the 4s sub-shell only has one electron while the 3d sub-shell has five and ten electrons respectively. This is because this is more stable.
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14
Q

What is the shape of an S sub-shell and a P sub-shell?

A
  • S: Spherical
  • P: Dumbbell shaped
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15
Q

Which elements don’t follow the octet rule?

A
  1. 8 > Boron
  2. 8 < Sulfur
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16
Q

Define coordinate / dative covalent bonding.

A

When one atom provides both electrons in a covalent bond.

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17
Q

How does solubility change as ionic charge increases?

A

It decreases.

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18
Q

Are metals soluble in water?

A

No, they don’t dissolve, they react.

19
Q

What shape and angle does a molecule with 0 LPs and 2 BPs have?

A

Shape: Linear
Angle: 180

20
Q

What shape and angle does a molecule with 0 LPs and 3 BPs have?

A

Shape: Trigonal planar
Angle: 120

21
Q

What shape and angle does a molecule with 1 LPs and 2 BPs have?

A

Shape: Non-linear
Angle: 119

22
Q

What shape and angle does a molecule with 0 LPs and 4 BPs have?

A

Shape: Tetrahedral
Angle: 109.5

23
Q

What shape and angle does a molecule with 1 LPs and 3 BPs have?

A

Shape: Trigonal pyramidal
Angle: 107

24
Q

What shape and angle does a molecule with 2 LPs and 2 BPs have?

A

Shape: Non-linear
Angle: 104.5

25
Q

What shape does a molecule with 0 LPs and 5 BPs have?

A

Shape: Trigonal bipyramidal

26
Q

What shape does a molecule with 0 LPs and 6 BPs have?

A

Shape: Octahedral

27
Q

Define electronegativity.

A

An atom’s ability to attract the electron density in a covalent bond to itself.

28
Q

Define bond polarity.

A

Difference in electronegativity between two bonded atoms.

29
Q

What is a dipole and when does a molecule have permanent dipole?

A

A dipole is the difference in charge as a result of bond polarity and a molecule had a permanent dipole when the charges don’t cancel out.

30
Q

What are the three types of intermolecular forces?

A
  1. Induced dipole-dipole interactions (London forces)
  2. Permanent dipole-dipole interactions
  3. Hydrogen bonds
31
Q

What types of bonds result in hydrogen bonds

A
  1. O-H
  2. N-H
  3. F-H
32
Q

What modifications can be made to the method of an experiment where you are trying to find the water of crystalisation to make it more accurate?

A

-Use a greater mass of hydrated salt
-Use a scale with a higher resolution
-Keep heating until mass no longer changes

33
Q

What is an acid?

A

Proton donor

34
Q

What is a base?

A

Proton acceptor

35
Q

What is an alkali?

A

Water soluble base, releases hydroxide ions in water

36
Q

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

A

A strong acid fully dissociates, while a weak acid partially dissociates

37
Q

What does amphoteric mean?

A

Something that can behave as an acid or a base

38
Q

What are the uses of titration?

A
  • Finding concentration of solution
  • Identification of unknown solution
  • Finding the purity of a substance
39
Q

What is a standard solution?

A

A solution of known concentration

40
Q

What are concordant titres?

A

Titres with 0.1cm⁻³ of each other

41
Q

Why is it important to fill the space below the tap in the burette before beginning an accurate titration?

A

It will fill during titration and cause titre to be too high and appear to have more moles of acid.

42
Q

Why does rinsing the inside of the conical flask with water improve the accuracy of each titre?

A

Ensures no solution is lost / ensures all reagents are in the reaction mixture.

43
Q

What indicators are used in titrations?

A

Phenolphthalein: Pink in strong alkalis, colourless once neutralised

Methyl orange: Orange in strong acids, colourless when neutralised

Chemistry OCR A (5 decks)

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