Group 3 Model answers Flashcards
Sodium and water
Reacts vigorously
Resulting solution high pH value 13-14
sodium floats on surface of water
fizzing, gives off hydrogen gas
Magnesium and water
Reacts very slowly at room temperature
Gives off few bubbles of H2 gas
Resulting solution pH of around 10 because magnesium hydroxide only sparingly soluble
slight white precipitate
What is oxidation state of period 3 elements in their oxides?
+3
Apart from sulfur which forms two
phosphorus pentoxide
P4O10
What type of structure is SiO2?
Giant covalent lattice
Sulfur flame colour
Blue
Magnesium flame colour
White
Sodium flame colour
Yellow
What does sulfur react with oxygen to make?
SO2
How is SO3 made?
SO2 is oxidised
Alkaline solutions of period 3 oxides
MgO and Na2O forming hydroxides
Neutral solutions of period 3 oxides
Al2O3 (amphoteric) and SiO2 (doesn’t dissolve but reacts as acidic oxide)
Why does Al2O3 not dissolve?
covalent character
Acidic solutions of period 3 oxides?
SO2 SO3 and P4O10
pH of phosphoric acid
0-1
pH of sulphurous acid
3-4
what forms sulphurous acid and what forms sulfuric acid?
SO2 -> sulfurous
SO3 -> sulfuric
What does sulfurous acid dissociate to?
partially to H+ and HSO3-
Acidic period 3 oxides
SiO2 P4O10 SO2 SO3
Aluminium oxide reacting as acid
Al2O3 + NaOH + 3H2O -> NaAl(OH)4
Silicon oxide reacting with NaOH
SiO2 + hot concentrated 2NaOH -> NaSiO3 +H2O
Phosphorus pentoxide reacting with Na2O
P4O10 + 6Na2O -> 4Na3PO4
SO2 reacting with NaOH step 1 step 2
NaOH + SO2 -> NaHSO3
NaHSO3 + NaOH -> Na2SO3 + H2O
NaOH reacting with SO3 step 1 step 2
NaOH + SO3 -> NaHSO4
NaHSO4 + NaOH -> Na2SO4 + H2O
