AS Chemistry - Inorganic P1 Corrections

Describe the structure and bonding in magnesium

• giant lattice of Mg²⁺ ions

• strong electrostatic attraction between cations and delocalised electrons

Give two observations for the reaction of Magnesium with steam

• white powder produced

• bright white flame

How would you improve the accuracy of making up a standard solution?

• weigh weighing boat, add solid, weigh, remove solid, weigh again

• invert volumetric flask several times

• wash beaker/stirring rod into flask

describe how a molecule has a specific shape (when it has lone pairs)

• lone pairs repel each other, and repel bonding pairs, more than bonding pairs repel each other

• so the lone pairs are as far apart as possible

• so the bond angle is reduced

how are ions detected in a TOF mass spectrometer?

positive ions collide with a negative plate gain an electron, producing a current

state the meaning of electron impact ionisation

when electrons are used to knock out an electron from the outer shell of a molecule

describe how a change in temperature affects the value of Kc

• changes value of Kc

• as forwards reaction is x

• so position of equilibrium shifts to oppose the change

explain why the 3rd ionisation energy of Mg is much higher than the 2nd ionisation energy of Mg

• electron is removed from lower energy level (2p instead of 3s)

• so electron removed is less shielded + feels stronger forces of attraction to nucleus

give some common titration errors and solutions

• too much indicator

  • may react and affect endpoint reading

  • use a smaller volume

• adding alkali until indicator just changes colour

  • acid may not have fully reacted

  • add alkali till permanent colour change

• measuring cyclinder

  • measuring cylinder is less accurate/has higher uncertainty

  • use volumetric pipette

why does CBr4 have a higher boiling point than CHBr3

• CBr4 has only van der waals forces

• CHBr3 has van der waals forces and permanent dipole-dipole forces

• CBr4 has a much higher Mr than CHBr3 so the VDW forces are stronger than the dipole dipole and VDW forces

give the HI balancing numbers for each reaction of HI

• 2 → SO2

• 6 → S

• 8 → H2S

suggest whether forward reaction results in increase/decrease moles of gas

• increase

• lower yield at higher pressure

• so equilibrium has shifted backwards to oppose increase

explain in terms of oxidation ability why displacement reactions of Br2 are not able to distinguish between Cl- and Br- ions

• bromine not a strong enough oxidising agent to displace chlorine

• or bromine

why is CCl4 non polar when the C-Cl bond is polar

• tetrahedral shape which is symmetrical

• so dipoles cancel out

how do you test for Mg?

• add NaOH

• white precipitate forms