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The highest oxides of the elements sodium to chlorine are separately added to water - CIE - A-Level Chemistry - Question 14 - 2011 - Paper 1
Question 14
The highest oxides of the elements sodium to chlorine are separately added to water. Which diagram best represents the pH of the resulting mixtures? A B C D
Worked Solution & Example Answer:The highest oxides of the elements sodium to chlorine are separately added to water - CIE - A-Level Chemistry - Question 14 - 2011 - Paper 1
Step 1
Which diagram best represents the pH of the resulting mixtures?
Answer
To determine the correct diagram representing the pH of the resulting mixtures when the highest oxides of sodium (Na2O) to chlorine (Cl2O7) are added to water, we need to consider the acidity or basicity of each oxide:
- Basic Oxides: Sodium oxide (Na2O) and magnesium oxide (MgO) are basic and will produce alkaline solutions, thus increasing the pH significantly when added to water.
- Amphoteric Oxides: Aluminum oxide (Al2O3) is amphoteric; depending on conditions, it can react with either acids or bases, but it might not significantly affect the pH in the same way as strong bases.
- Acidic Oxides: Phosphorus pentoxide (P4O10), sulfur trioxide (SO3), and chlorine heptoxide (Cl2O7) are acidic. When added to water, they will cause a decrease in pH, making the solution more acidic.
- Graph Analysis: Based on these characteristics, we observe that the pH will initially rise due to the basic oxides (A and B), and then sharply decline with the introduction of acidic oxides. Specifically, diagram B shows an initial rise followed by a gradual decline, which aligns with the expected behavior of the various oxides.
Thus, the correct answer is Diagram B.