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This question is about oxides - AQA - A-Level Chemistry - Question 2 - 2020 - Paper 3
Question 2
This question is about oxides. Sodium oxide forms a solution with a higher pH than magnesium oxide when equal amounts, in moles, of each oxide are added separately ... show full transcript
Worked Solution & Example Answer:This question is about oxides - AQA - A-Level Chemistry - Question 2 - 2020 - Paper 3
Step 1
State why both oxides form alkaline solutions.
Answer
Both sodium oxide and magnesium oxide react with water to form hydroxide ions. This reaction produces alkaline solutions. The general equations for the reactions can be written as:
ightarrow 2 ext{NaOH}$$ $$ ext{MgO} + ext{H}_2 ext{O} ightarrow ext{Mg(OH)}_2$$Step 2
Suggest why sodium oxide forms a solution with a higher pH than the solution formed from magnesium oxide.
Answer
Sodium hydroxide is more soluble in water than magnesium hydroxide. As a result, when equal amounts of sodium oxide and magnesium oxide are dissolved in water, sodium oxide will produce a greater concentration of hydroxide ions ( ext{OH}^-), leading to a higher pH solution.
Step 3
Step 4
Give two equations to show how the vanadium(V) oxide acts as a catalyst in this process.
Answer
The equations representing the catalytic process with vanadium(V) oxide are:
ightleftharpoons ext{V}_2 ext{O}_5 + ext{SO}_3 ext{V}_2 ext{O}_5 + ext{SO}_3 ightleftharpoons ext{V}_2 ext{O}_5 + ext{SO}_2$$