Period 3 Flashcards
Describe a method for determining the melting point of the sample
Sample in melting point apparatus
Heat slowly to establish melting point range
Lower melting point indicates presence of impurities
Describe a test you could carry out in a test tube to distinguish between Na2O and P4O10
React with water
Add litmus paper and universal indicator and measure pH
NaOH 12-14 pH
H3PO4 0-2 pH
Write ionic equation for P4O10 with excess NaOH
P4O10 + 12OH- -> 4PO43- + 6H2O
Write the two equations to show amphoteric nature of Al2O3
Al2O3 + 6HCl -> 2AlCl3 + 3H2O
Al2O3 + 2NaOh +3H2O -> 2NaAl(OH)4
Explain using an equation why SiO2 is classified as an acidic oxide
Reacts with alkalis
SiO2 + 2NaOH -> Na2SiO3 + H2O
Give two physical properties of SiO2
Insoluble
Hard
High melting point
Write an equation when ions are formed when SO2 reacts with water
SO2 + H2O -> H+ + HSO3-
Suggest why white phosphorus is stored under water
Prevents reacting with air
Suggest why it is usually represented by P4O10 rather than P2O5
Molecular formula is P4O10
Explain why an excess of MgO can be used for this neutralisation
MgO is sparingly soluble
Observations when Mg burns in O2
Bright white flame
White fumes
Observations when S burns in O2
Blue flame
Misty fumes
How to show Al2O3 has ions
Heat until molten
Conducts electricity
Why a thin layer of Al2O3 protects Al from corrosion in moist air
Insoluble in water
Ionic equation to show Al2O3 reacting with HCl
Al2O3 + 6H+ -> 2Al3+ + 3H2O