Why does pH increase when hydroxide ions are added to an acidic solution?
Answer and explanation
Correct answer: Because hydroxide ions reduce hydrogen ions by forming water
An acidic solution contains a relatively high concentration of hydrogen ions, H⁺, and its pH is low. Added hydroxide ions react with hydrogen ions in the neutralisation reaction H⁺ + OH⁻ → H₂O. This removes free H⁺ ions from the solution, so the hydrogen-ion concentration decreases and pH rises. The solution may eventually approach neutrality, depending on the amounts added. Options B, C, and D do not describe this reaction. Therefore A is correct.
Frequently asked questions
What is the correct answer to this question?
Because hydroxide ions reduce hydrogen ions by forming water
Why is this the correct answer?
An acidic solution contains a relatively high concentration of hydrogen ions, H⁺, and its pH is low. Added hydroxide ions react with hydrogen ions in the neutralisation reaction H⁺ + OH⁻ → H₂O. This removes free H⁺ ions from the solution, so the hydrogen-ion concentration decreases and pH rises. The solution may eventually approach neutrality, depending on the amounts added. Options B, C, and D do not describe this reaction. Therefore A is correct.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Chemical Substances – Nature and Behaviour. Topic: Acids, Bases, and Salts.
