Why does pH increase when hydroxide ions are added to an acidic solution?
Answer and explanation
Correct answer: They combine with hydrogen ions to form water
pH is related to hydrogen-ion concentration: pH = −log[H+]. An acidic solution contains excess H+ ions. When OH− ions are added, they neutralise these ions according to H+ + OH− → H2O. The hydrogen-ion concentration consequently decreases, so the solution becomes less acidic and its pH increases. Option A correctly states this neutralisation. The other options do not describe the relevant ionic reaction or pH change.
Frequently asked questions
What is the correct answer to this question?
They combine with hydrogen ions to form water
Why is this the correct answer?
pH is related to hydrogen-ion concentration: pH = −log[H+]. An acidic solution contains excess H+ ions. When OH− ions are added, they neutralise these ions according to H+ + OH− → H2O. The hydrogen-ion concentration consequently decreases, so the solution becomes less acidic and its pH increases. Option A correctly states this neutralisation. The other options do not describe the relevant ionic reaction or pH change.
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.
