The acidic/basic nature of the Period 3 oxides

Question 1

How does sodium and magnesium oxides react with acidS?

Answer 1

• give salt and water only
• e.g. MgA + H2O

Question 2

What is unusual about aluminium oxide? How does it react? gvie examples

Answer 2

• reacts with both acid and alkalis
• is an amphoteric oxide
• e.g. when reacted with chlorine, aluminium chloride is formed
• e.g. when reacted with hot, conc, sodium hydroxide, sodium aluminate is formed (2NaAl(OH)₄)

Question 3

Silicon(IV) oxide is insoluble in water. Explain, using an equation, why silicon(IV) oxide is classified as an acidic oxide.

Answer 3

• reacts with strong bases
  
  • e.g. hot conc NaOH
• SiO₂ + 2NaOH → Na₂SiO₃ + H₂O

Question 4

How is iron produced?

Answer 4

• at high temp inside blast furnace
• calcium oxides reacts with silicon dioxide (sand) to produce liquid slag, calcium silicate
• example of the acidic silicon dioxide reacting with a base

Question 5

What happens when P4O10 reacts with an alkali?:

Answer 5

• really the reaction of phosphoric (V) acid H₃PO₄
  
  • ​this is formed when phosphorus pentoxide react with water
• phosphoric acid has 3 -OH groups and each of these has an acidic hydrogen atom so will react with NaOH in 3 stages
• each hydrogen in turn reacts with a hydroxide ion and is replaced by a sodium ion
  
  • ovarall
    
    • 3NaOH (aq) + H₃PO₄ (aq) → Na₃PO₄ (aq) + 3H₂O

Question 6

What happens when sulfur dioxide reacts with a base?

Answer 6

• add NaOH to aqueous sulfur dioxide first sodium hydrogensulfate(IV) is form (NaHSO3 (aq))
• then reacts again to form sodium sulfate(IV) (Na2SO3 (aq)) and water

Question 7

How could you determine between a sample of phosphorus oxide and sodium oxide>

Answer 7

• P4O10 is acidic, NaO2 is alkaline
• add litmus measure pH
• litmus blue with sodium oxide and red with P4O10