The oxides CaO, CO₂, Na₂O and N₂O₄ are placed in water to form four separate solutions - HSC - SSCE Chemistry - Question 5 - 2015 - Paper 1
Question 5
The oxides CaO, CO₂, Na₂O and N₂O₄ are placed in water to form four separate solutions.
Which row of the table correctly indicates the solutions with pH less than 7... show full transcript
Worked Solution & Example Answer:The oxides CaO, CO₂, Na₂O and N₂O₄ are placed in water to form four separate solutions - HSC - SSCE Chemistry - Question 5 - 2015 - Paper 1
Step 1
Identify acidic and basic oxides
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Answer
To determine the pH of each oxide solution in water, it is essential to classify the oxides as either acidic or basic.
CaO is a basic oxide and will produce a solution with pH greater than 7 when dissolved in water, forming Ca(OH)₂.
CO₂ is an acidic oxide, producing carbonic acid (H₂CO₃) in water, resulting in a solution with pH less than 7.
Na₂O is also a basic oxide, creating a solution with pH greater than 7 as it forms NaOH upon dissolution.
N₂O₄ is an acidic oxide, forming nitric acid (HNO₃) in water, leading to a solution with pH less than 7.
Step 2
Match solutions with corresponding pH levels
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Answer
Based on the classification:
pH less than 7: CO₂ and N₂O₄
pH greater than 7: CaO and Na₂O
Step 3
Conclusion
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Answer
The correct row from the table that indicates solutions with pH less than 7 and those with pH greater than 7 is option (A), which lists CO₂ and N₂O₄ as having pH less than 7, and CaO and Na₂O as having pH greater than 7.
