3.2.4 - properties of period 3 elements and their oxides Flashcards
what is the shape of phosphoric acid (H3PO4)?
tetrahedral
what is the shape of sulphuric acid (H2SO4)?
tetrahedral
what is the shape of sulphurous acid (H2SO3)?
trigonal bipyramidal (has one lone pair)
what observations are made when sodium reacts with water?
fizzing, Na moves on surface of water
what is the pH of the solution formed when sodium reacts with water?
13 (alkaline)
what is the equation for the reaction of sodium and water?
2Na (s) + 2H2O (l) –> 2NaOH (aq) + H2
what observations are made when magnesium reacts with water?
there is a slow release of bubbles on the surface of the Mg
what is the pH of the solution formed when magnesium reacts with water?
11 (alkaline)
what is the equation for the reaction of magnesium and water?
Mg (s) + 2H2O (l) –> Mg(OH)2 (aq) + H2 (g)
what observations are made when magnesium reacts with steam?
Mg burns with a bright white flame, white solid forms, flammable gas forms which easily ignites
what is the equation for the reaction of magnesium and steam?
Mg (s) + H2O (g) –> MgO (s) + H2 (g)
what observations are made when sodium reacts with oxygen?
yellow flame, white solid forms
what is the equation for the reaction of sodium and oxygen?
4Na (s) + O2 (g) –> 2Na2O (s)
what observations are made when magnesium reacts with oxygen?
bright white light, white solid forms
what is the equation for the reaction of magnesium and oxygen?
2Mg (s) + O2 (g) –> 2MgO (s)
what observations are made when aluminium reacts with oxygen?
white sparks
what is the equation for the reaction of aluminium and oxygen?
4Al (s) + 3O2 (g) –> 2Al2O3 (s)
why does aluminium appear unreactive in the presence of oxygen, even though it is reactive?
the oxygen oxidises the surface of the aluminium to form a layer of aluminium oxide, which is unreactive
what observations are made when silicon reacts with oxygen?
orange sparks
what is the equation for the reaction of silicon and oxygen?
Si (s) + O2 (g) –> SiO2 (s)
what observations are made when phosphorus reacts with oxygen?
it spontaneously ignites in O2
what is the equation for the reaction of phosphorus and oxygen?
P4 (s) + 5 O2 (g) –> P4O10 (s)
what observations are made when sulfur reacts with oxygen?
pale blue flame, colourless choking gas produced
what is the equation for the reaction of sulfur and oxygen?
S (s) + O2 (g) –> SO2 (g)
2S (s) + 3O2 (g) –> 2SO3 (g)
what is the trend in the melting points of the oxides of the elements Na-S?
they increase from sodium oxide (giant ionic) to magnesium oxide (giant ionic) to aluminium oxide (giant ionic)
aluminium oxide has the highest
they decrease from aluminium oxide to silicon dioxide (giant covalent) to phosphorus oxide (simple molecular) to sulfur dioxide (simple molecular)
from highest to lowest - aluminium oxide, silicon dioxide, magnesium oxide, sodium oxide, phosphorus oxide, sulfur dioxide
what observations are made when sodium oxide reacts with water, and what is the pH of the solution formed?
a vigorous exothermic reaction which forms an alkaline solution
pH = 13-14
what is the equation for the reaction of sodium oxide and water?
Na2O (s) + H2O (l) –> 2NaOH (aq)
what observations are made when magnesium oxide reacts with water, and what is the pH of the solution formed?
forms a sparingly soluble suspension, and undissolved MgO forms a white solid
pH = 8-10
what is the equation for the reaction of magnesium oxide and water?
MgO (s) + H2O (l) –> Mg(OH)2 (aq)
what observations are made when aluminium oxide reacts with water, and what is the pH of the solution formed?
it is insoluble in water so there is no visible change (very strong ionic bonds can’t be broken)
what observations are made when silicon dioxide reacts with water, and what is the pH of the solution formed?
it is insoluble in water so there is no visible change (strong covalent bonds can’t be broken)
what observations are made when phosphorus oxide reacts with water, and what is the pH of the solution formed?
violent exothermic reaction, dissolves to form colourless solution
pH = 0-1
what is the equation for the reaction of phosphorus oxide and water?
P4O10 (s) + 6H20 (l) –> 4H3PO4 (aq)
what observations are made when sulfur dioxide reacts with water, and what is the pH of the solution formed?
dissolves in water to form colourless acidic solution
pH = 1-3
what is the equation for the reaction of sulfur dioxide and water?
SO2 (s) + H2O (l) –> H2SO3 (aq)
what observations are made when sulfur trioxide reacts with water, and what is the pH of the solution formed?
dissolves in water to form colourless acidic solution
pH = 0-1
what is the equation for the reaction of sulfur trioxide and water?
SO3 (s) + H2O (l) –> H2SO4 (aq)
what is formed when phosphorus oxide reacts with water?
phosphoric acid
what is formed when sulfur dioxide reacts with water?
sulphurous acid
what is formed when sulfur trioxide reacts with water?
sulfuric acid
how do sodium oxide and magnesium oxide form hydroxide ions in a solution?
there is sufficient energy released in the reaction with water to overcome the ionic bonds between ions so the compounds break down
they release O^2- ions which react with water to form OH^- ions (O^2- + H2O –> 2OH^-)
why is silicon dioxide insoluble in water?
there is insufficient energy supplied by the attraction between water molecules and silicon dioxide to overcome the many strong covalent bonds between atoms
what is the formula of a sulphite ion?
SO3^2-
what is the formula of a silicate ion?
SiO3^2-
what is the formula of an aluminate ion?
Al(OH)4^-
which period 3 oxides are basic oxides?
sodium oxide and magnesium oxide
what do basic oxides react with?
acids
what is produced when basic oxides react with acids?
a soluble salt and water
what makes aluminium oxide different to the other period 3 oxides?
it is amphoteric, meaning it reacts with acids and bases
what is produced when aluminium oxide reacts with an acid or base?
acid - soluble salt and water
base - a metal aluminate
what is the normal and ionic equation for the reaction of aluminium oxide, water and sodium hydroxide?
Al2O3 (s) + 2NaOH (aq) + 3H2O (l) –> 2NaAl(OH)4 (aq)
Al2O3 (s) + 2OH^- (aq) + 3H2O (l) –> 2Al(OH)4^- (aq)
which period 3 oxides are acidic oxides?
phosphorus oxide, silicon dioxide, sulfur dioxide and trioxide
what do acidic oxides react with?
bases
what is produced when acidic oxides react with bases?
soluble salts and often one or more other products ie. water if reacting with metal hydroxide, carbon dioxide if reacting with metal carbonate
what kind of salt will form when silicon dioxide reacts with a base?
a silicate
what kind of salt will form when sulphur dioxide reacts with a base?
a sulphite
what kind of salt will form when sulphur trioxide reacts with a base?
a sulphate
