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Flashcards in Module 2 Deck (68):
1

What is an isotope?

Isotopes are atoms of the same element with different numbers of neutrons and different masses

2

What is a positive ion?

Cation

3

What is an anion?

A negative ion

4

State the definition of relative atomic mass

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

5

State the definition of relative isotopic mass

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

6

What does the weighted mean mass take account of?

The percentage abundance of each isotope
The relative isotopic mass of each isotope

7

What is a binary compound?

A compound which consists of two elements only

8

What is a polyatomic ion?

An ion which contains more than one element bonded together

9

What is Avogadro’s constant?

The number of particles in each mole of carbon-12

6.02x10^23

10

Assumptions for the calculations of water of crystallisation

All water has been lost

No further decomposition

11

How are standard solutions prepared?

Dissolve an exact mass of the solute in a solvent and make up the solution to an exact volume

12

How do you find concentration in gdm^-3?

m = n X M
n= concentration in Mol dm^-3

13

What is the molar gas volume?

The volume per mole of gas molecules at a stated temperature and pressure

14

How do you convert between the amount of moles of gas and the volume of the gas?

n = volume(dm-3) / 24

Or

n = volume(cm-3) / 24000

15

Assumptions of an ideal gas

Random motion
Elastic collisions
Negligible size
No intermolecular forces

16

Units for the equation
pV=nRT

p = Pa
V = m^3
n = mol
R = 8.31 J mol -1 K -1
T = K

17

How do you calculate atom economy?

Sum of molar masses of desired products / sum of molar masses of all products

x100

18

What kind of acid completely dissociates, releasing all of its hydrogen atoms into solution as H+ ions?

Strong acid

19

What does a base do?

Neutralises an acid to form a salt

20

What is an alkali?

A base that is dissolved in water releasing hydroxide ions (OH-) into the solution

21

Acid + alkali =

Salt + water

22

Uncertainty of a 100cm^3 volumetric flask

+-0.2cm^3

23

Uncertainty of a 250cm^3 volumetric flask

+-0.3cm^3

24

Tolerances of a 10cm^3 and a 25cm^3 pipette

+- 0.04

+-0.06

25

Tolerances of a 50cm^3 burette

+-0.1

26

What must titres agree within to calculate the mean titre?

10cm^3

27

Analysing titrations

Work out the amount in mol of the solute in the solution for which you know both the concentration and volume

Use the equation to work out the amount in mol of the other solute

Work out the unknown information

28

Oxidation number of elements

Zero

29

Oxidation number of H in metal hydrides

-1

30

Oxidation number of O in peroxides

-1

31

Oxidation number of O bonded to F

+2

32

What do Roman numerals represent?

The oxidation state of the element

33

NO2-

Nitrate (III)

(Nitrite)

+3

34

NO3-

Nitrate (V)

+5

35

What is oxidation?

Addition of oxygen

Loss of electrons

Increase in oxidation number

36

Metal + acid =

Salt + hydrogen

37

What is an atomic orbital?

A region around the nucleus that can hold up to two electrons, with opposite spin

38

What is the shape of an S orbital and how many electrons can it hold?

Sphere

Up to 2 electrons

39

What is the shape of a P orbital and how many electrons can it hold?

Dumb-bell

Up to 6 electrons

40

How do orbitals fill?

In order of increasing energy

41

Why does the 4s sub-shell fill before the 3d sub-shell?

4s subshells are at a lower energy level than 3d

42

In what direction do ions attract oppositely charged ions?

All directions

43

Properties of ionic compounds

All solids at room temperature

Melting points are higher for lattices containing ions with greater ionic charge

Many dissolve in polar solvents. In a compound with large charges the ionic attraction may be too strong for water to be able to break down the lattice.

Only conducts electricity when melted or in aqueous solution.

44

What is covalent bonding

The strong electrostatic attraction between a shared pair of electrons and the nuclei of bonded atoms.

The overlap of atomic orbitals.

45

What is the attraction in a covalent bond?

Localised, it acts only between the shared pair of electrons and the nuclei of the two bonded atoms

46

What is a double covalent bond?

The electrostatic attraction is between two shared pairs of electrons and the nuclei of the bonding atoms

47

What is a dative covalent / coordinate bond?

A covalent bond in which the shared pair of electrons has been supplied by one of the bonding atoms only.

The shared pair was originally a lone pair of electrons on one of the bonded atoms.

48

How are average bond enthalpy and covalent bond strength related?

The larger the value of the average bond enthalpy, the stronger the covalent bond

49

Shape of a molecule with 4 bonded pairs and 0 lone pairs

Tetrahedral
109.5

50

Shape of a molecule with 3 bonded pairs and 1 lone pair

Pyramidal
107

51

Shape of a molecule with 2 bonded pairs and 2 lone pairs

Non-linear
104.5

52

Shape of a molecule with 2 bonded pairs

Linear
180

53

Shape of a molecule with 3 bonded pairs

Trigonal planar
120

54

Shape of a molecule with 6 bonded pairs

Octahedral
90

55

Why do lone pairs repel more strongly than bonded pairs?

Lone pairs are slightly closer to the central atoms and occupy more space

56

What is electronegativity?

The attraction of a bonded atom for the pair of electrons in a covalent bond

57

Pauling electronegativity values

Electronegativity increases up and right of the periodic table

Across the periodic table nuclear charge increases and atomic radius decreases

58

Electronegativity difference for a covalent bond, polar covalent bond, and an ionic bond

0
0-1.8
>1.8

59

What is a non polar bond?

The bonded electron pair and shared equally between the bonded atoms

60

When will a bond be non polar?

The bonded atoms are the same

Or

The bonded atoms have the same or similar electronegativity

61

What is a polar bond?

The electron pair is shared unequally between the bonded atoms.
The atoms are different and have different electronegativity values.

62

How are induced dipole-dipole interactions formed?

Movement in electrons produced a changing dipole in a molecule

At any instant and instantaneous dipole will exist but it’s position constantly changing

The instantaneous dipole induces a dipole on a neighbouring molecule

The induced dipole induces further dipoles on neighbouring molecules, which then attract one another

63

How are induced dipole-dipole interactions affected when there are more electrons in each molecule?

The larger the induced and instantaneous dipoles

The greater the induced dipole-dipole interactions

The stronger the attractive forced between molecules

More energy is needed to over come intermolecular forces so boiling point increases

64

When will a molecule have permanent dipole-dipole interactions?

When the atoms have permanent dipoles

65

What is a simple molecular substance?

Simple molecules in the solid state.

The molecules are held in place by weak intermolecular forces but the atoms within each molecule are bonded together strongly by covalent bonds

66

Properties of simple molecular substances

Low meeting and boiling points

Non-polar simple molecular substances:
•Soluble in non-polar solvents
•Insoluble in polar solvents

Polar simple molecular substances:
•solubility depends on the strength of the dipole and can be hard to predict

Non-conductors of electricity

67

Where is a hydrogen bond found?

Between molecules containing:
•An electronegative atom with a lone pair of electrons
•A hydrogen atom attached to an electronegative atom

68

What are the anomalous properties of water?

Ice is less dense than water:
•hydrogen bonds hold water in an open lattice structure

Relatively high melting point and boiling point

Relatively high surface tension

Relatively high viscosity