Definitions and standard answers:

Standard answers Module 1A

1)      Isotope:  Same number of protons and electrons, different number of neutrons

2)      Acid:  Proton donor

3)      Base:  proton acceptors

4)      Strong acid:  Dissociates fully in water

5)      Weak acid:  Partially dissociates in water

6)      Salt:  When the H+ ion in an acid is replaced with a metal (ammonium) ion

7)      Alkali:  Dissociate to give hydroxide ions in water

8)      Acid reactions:

Metal + acid Salt + hydrogen

Metal oxide + acid Salt + water

Metal hydroxide + acid Salt + water

Metal carbonate + acid Salt + water = carbon dioxide

9)      % element = No of that element  x  Ar  x  100

Mr

 

10)   Oxidation is loss of electrons

11)   Reduction is gain of electrons

Standard answers Module 1B

1)      Relative isotopic mass:  mass of an atom of an isotope compared with 1/12 of the mass of an atom of 12C

2)      Relative atomic mass, Ar:  weighted mean mass of an atom of an element compared with 1/12 of the mass of an atom of 12C

3)      Relative molecular mass, Mr:  weighted mean mass of an molecule compared with 1/12 of the mass of an atom of 12C

4)      Relative formula mass, Mr:  weighted mean mass of a formula unit compared with 1/12 of the mass of an atom of 12C

5)      RAM = (%  x  Ar)  +  (%  x  Ar)

100

6)      Empirical formula:  simplest whole number ratio of atoms of each element in a compound

7)      Molecular formula:  actual whole number ratio of atoms of each element in a compound

8)      Moles (s)     = mass (g)

             Mr

 

(Aq) = Conc (mol dm-3)  x  Vol (dm3)

 

(g)  =  Vol (dm3)

             24 (dm3)

Standard answers Module 2A

1)      First ionisation energy:  energy required to remove 1 electron from each atom in a mole of gaseous atoms to form 1 mole of gaseous 1+ ions

2)      Atomic orbital:  region in space around the nucleus that can contain 2 electrons with opposite spins

 

Standard answers Module 2B

1)      Ionic bonding:  Electrostatic force of attraction between oppositely charged ions

2)      Covalent bond:  Formed by a pair of shared electrons

3)      Dative covalent bond:  Formed by a pair of shared electrons where both electrons are provided by one atom

4)      What determines the shape of a molecule:

         Pairs of electrons repel as far as possible

         This determines the shape

         Lone pairs repel more than bonding pairs as closer to central atom

         Each lone pair reducing the bond angle by 2.5o as it is closer to the central atom

3BP (areas)

4BP

3BP / 1LP

2BP / 2LP

2 Areas (4BP)

6BP

 

 

 

 

 

Trigonal planar

Tetrahedral

Pyramidal

Non - linear

Linear

Octahedral

 

5)      How does the addition of H+ ion change shape of ammonia (water)

3BP / 1LP

 

4BP

 

The addition of a datively bonded H+ ion uses the lone pair converting it to a bonding pair (similar for water)

Trigonal planar

 

Tetrahedral

 

Standard answers Module 2C

1)      Electronegativity:  The power of an atom to attract bonding pairs of electrons towards itself

 

2)      IMF VDW: between atoms of similar electronegativity

         Uneven distribution of electrons

         Instantaneous dipole

         Induced dipole

         Weak force of attraction

 

3)      IMF Permanent dipole dipole forces of attraction: 

Is between molecules with a permanent dipole 

 

 

 

 

 

 

4)      IMF Hydrogen bonding:

         Dipoles

         O,N,F bonded to H

         LP on O,N,F

         Dotted line between LP and H

         Labelled

 

 

5)      Anomalous properties of water:

         Unusually high melting / boiling point H bonding is strongest IMF, more energy needed to overcome

         Ice less dense than water H bonds are longer than covalent bonds

         Surface tension extensive H bonds across the surface of water

 

6)      Metallic bonding:

         LABELLED DIAGRAM

         Electrostatic  forces of attraction between metal ions and delocalised electrons

 

7)      Conductivity of metals:

         Electrons are free to move

 

8)      Conductivity of ionic compounds:

         Solid does not conduct as ions in a fixed position

         Molten / dissolved does conduct electricity as ions are free to move

Standard answers Module 3A

1)      Explain the trend in boiling point of Gp 1 3 metals:

         As you go across Period, metal ions have a larger charge

         Also has more delocalised electrons

         Attraction is greater between larger ionic charge and more delocalised electrons

 

2)      State and explain the trend in atomic radii across a Period:

         Across period nuclear charge increases

         Electrons in same shell, shielding remains the same

         Greater attraction

         Atomic radius decreases

 

3)      State and explain the trend in first ionisation energies across a Period:

         Across period nuclear charge increases

         Electrons in same shell, shielding remains the same

         Greater attraction

         Atomic radius decreases

         Electrons more difficult to remove

4)      State and explain the trend in Atomic radii down a Group:

         More electron shells

         Atomic radii increases

 

5)      State and explain the trend in ionisation energies down a Group:

         More electron shells

         More shielding

         Atomic radii increases

         Attraction decreases despite an increase in the nuclear charge

 

6)      State and explain the trend in melting / boiling points across a period:

Gp 1-3:

         Increases

         Metal ions have a larger charge

         Also has more delocalised electrons

         Attraction is greater between larger ionic charge and more delocalised electrons

Gp 4:

         Highest

         Giant covalent structure, extensive strong covalent bonds

         Lots of energy required to break covalent bonds

Gp 5-7:

         Low

         Simple molecular weak IMF VDW

         Little energy required

Gp 0:

         Lowest

         Atomic weak IMF VDW

         Little energy required

Standard answers Module 3B

1)      State and explain the reactivity as you go down Gp 2:

         Reactivity increases down group

         Atomic radius increases due to more shells

         More inner shells, shielding

         Overall attraction decreases

         Easier to remove outer electrons

 

2)      State and explain the alkalinity / solubility of Gp 2 hydroxides:

         Solubility increases down the group

         More hydroxide ions released

         M(OH)2(s)  +  aq    M2+(aq)  +  2OH-(aq)

         More hydroxides = more alkaline

 

3)      State the ease of the decomposition of Gp 2 carbonates:

         Ease of decomposition decreases down the group

 

 

Standard answers Module 3C

1)      State and explain the trend in the boiling points down Gp7:

         Increases as you down the group

         Due to greater number of electrons

         Causing stronger VDW forces of attraction

 

2)      Colours of the halogens

 

Cl2

Br2

I2

Aq

pale green

orange

brown

Solvent

Pale green

orange

purple

 

3)      Precipitation reactions of the halides

 

Cl-

Br-

I-

AgNO3

White ppt

Cream ppt

Yellow ppt

Ammonia

Dissolves in dil

Dissolves in conc

Insoluble

 

4)      State and explain the reactivity as you go down Gp 7:

         Reactivity decreases down group

         Atomic radius increases due to more shells

         More inner shells, shielding

         Overall attraction decreases

         Harder to capture an electron

 

4)      Disproportionation:  Has been both oxidised and reduced