Chemistry of P-block Flashcards
What are the two oxidation states of the p-block elements?
The group number and two less.
What is the trend in oxidation states of the p-block elements?
The stability of the lower oxidation state increases down the group due to the inert pair effect.
What is the inert pair effect?
The tendency of the s2 electrons in an atom to stay paired leading to a lower oxidation state.
What p-block elements utilise the inert pair effect?
Period three and below as they have access to a vacant d-orbital that they can promote electrons to in order to form more bonds.
What is octet expansion?
The ability for some atoms to use vacant d-orbitals to have more than 8 electrons in their valence shell.
What are amphoteric oxides?
Oxides that can react with both acids and bases.
How do group three elements gain a full outer shell?
By forming co-ordinate bonds with other molecules to gain more electron pairs and form dimers. AlCl3 + AlCl3 —> Al2Cl6
What bonds are isoelectronic?
The boron-nitride bond and the carbon-carbon bond as they have very similar atomic radii.
What is hexagonal boron nitride analogous to?
Graphite.
Describe hexagonal boron nitride
Hexagonal sheets lying directly above one another
Weak forces between layers
No delocalised electrons, insulator and substrate for semiconductors
Boron nitride is polar due to differences in electronegativity
What is cubic boron nitride analogous to?
Diamond.
Describe cubic boron nitride
Tetrahedral structure- hard with high melting point
Used for wear-resistant coatings and in industrial abrasives
Describe CO
Carbon monoxide is the only stable compound with carbon in the +2 oxidation state and will act as a reducing agent as it is easily oxidised from +2 to +4.
What is the most stable oxide of carbon?
CO2, as the +4 oxidation state of C is more stable.
What is the most stable oxide of lead?
PbO, as the +2 oxidation state of Pb is more stable due to the inert pair effect.
Describe PbO2
It will act as an oxidising agent as it becomes reduced from +4 to +2.
What type of oxide is CO2?
An acidic oxide as it will react with alkalis to form a salt of carbonate or hydrogencarbonate.
What type of oxide is PbO?
An amphoteric oxide as it reacts with both acids and bases.
What are tetrachlorides?
Colourless liquids containing individual covalent molecules such as CCl4 and SiCl4. They are tetrahedral due to the 8 electrons in the valence shell.
Describe the reaction of CCl4 in water
Unreactive due to the absence of d-orbitals in the valence shell, the octet cannot expand.
Describe the reaction of SiCl4 in water
Very reactive, undergoing a hydrolysis reaction producing fumes of HCl gas and silicon dioxide precipitate. This increased reactivity is due to silicon having available d-orbitals for water to form co-ordinate bonds with due to octet expansion.
Describe the reaction of Pb2+ with aqueous hydroxide ions.
White precipitate of Pb(OH)2 formed.
Describe the reaction of Pb2+ with excess aqueous hydroxide
The white precipitate of Pb(OH)2 redissolves to make [Pb(OH)4]2-.
Describe the reaction of Pb2+ with aqueous chlorine
A dense white precipitate of PbCl2 is formed.
Describe the reaction of Pb2+ with aqueous iodine
A dense yellow precipitate of PbI2 is formed.
Describe the group 7 elements
Diatomic molecules, containing elements in all three physical states. All elements are non-metals.
Describe the oxidising power of the halogens
Chlorine is the strongest oxidising agent, with oxidising power decreasing down the group.
Give an example reaction of chlorine being an oxidising agent
Cl2 + 2Br- –> Br2 + 2Cl-
What is the general observation when sodium halide is added to concentrated sulphuric acid?
The hydrogen halide is formed as a steamy gas.
What is the equation for the reaction of sulphuric acid and sodium chloride?
NaCl (s) + H2SO4 (conc.) –> NaHSO4 (s) + HCl (g)
What is the equation for the reaction of sulphuric acid and sodium bromide?
NaBr (s) + H2SO4 (conc.) –> NaHSO4 (s) + HBr (g)
What is the equation for the reaction of sulphuric acid and sodium iodide?
NaI (s) + H2SO4 (conc.) –> NaHSO4 (s) + HI (g)
What is the further redox reaction between hydrobromic acid and hydrochloric acid?
2HBr (s) + H2SO4 (conc.) –> SO2 (g) + Br2 (g) + 2H2O (l)
What is the further redox reaction between hydrogen iodide and hydrochloric acid?
2HI (s) + H2SO4 (conc.) –> SO2 (g) + I2 (s) + 2H2O (l)
What observations are seen in the reaction between sodium chloride and concentrated sulphuric acid?
Steamy fumes of HCl.
What observations are seen in the reaction between sodium bromide and concentrated sulphuric acid?
Steamy fumes of HBr and orange fumes of Br2.
What observations are seen in the reaction between sodium iodide and concentrated sulphuric acid?
Steamy fumes of HI, purple fumes of I2, rotten egg smell (H2S) and a yellow solid (S).
What is a disproportionation reaction?
A reaction where one element ends up in two different compounds, one with a higher oxidation state and one with a lower oxidation state.
What is the reversible reaction created when chlorine is bubbled through water?
Cl2 (g) + H2O (l) ⇌ HCl (aq) + HOCl (aq)
What is the reaction created when chlorine is bubbled through alkaline sodium hydroxide?
Cl2 (g) + 2OH- (aq) –> Cl- (aq) + OCl- (aq) +H2O (l)
What is the reaction created when chlorine is bubbled through concentrated sodium hydroxide?
3Cl2 (g) + 6OH- (aq) –> 5Cl- (aq) + ClO3- (aq) + 3H2O (l)
What is a common use of chlorine?
It is used it bleaches as it has strong oxidising power.
What is a common use of the ClO- ion?
It is used in chlorination of drinking water, due to its ability to oxidise microbe cells and kill bacteria.
Why does AlCl3 usually exist as the dimer Al2Cl6?
As Al has six electrons in the outer shell, and is therefore electron deficient. To gain a full outer shell of electrons its accepts a lone pair from a chlorine in another molecules.
What is the overall equation for using CO in a blast furnace?
Fe2O3 + 3CO –> 2Fe + 3CO2
