A solution turns blue litmus red and gives a colourless gas with zinc metal. Which ion will mainly be present in this solution?
Answer and explanation
Correct answer: Hydrogen ion, \(\mathrm{H^+}\)
Blue litmus turning red shows that the solution is acidic. An acidic solution contains hydrogen ions, \(\mathrm{H^+}\). Zinc reacts with these ions to release colourless hydrogen gas: \(\mathrm{Zn + 2H^+ \rightarrow Zn^{2+} + H_2}\). Hence, \(\mathrm{H^+}\) is the correct option. \(\mathrm{OH^-}\) is associated with basic solutions; \(\mathrm{Cl^-}\) can occur in HCl but does not produce the acidic behaviour. Exam tip: Blue litmus changing to red and \(\mathrm{H_2}\) evolution with a metal are key tests for an acid.
Frequently asked questions
What is the correct answer to this question?
Hydrogen ion, \(\mathrm{H^+}\)
Why is this the correct answer?
Blue litmus turning red shows that the solution is acidic. An acidic solution contains hydrogen ions, \(\mathrm{H^+}\). Zinc reacts with these ions to release colourless hydrogen gas: \(\mathrm{Zn + 2H^+ \rightarrow Zn^{2+} + H_2}\). Hence, \(\mathrm{H^+}\) is the correct option. \(\mathrm{OH^-}\) is associated with basic solutions; \(\mathrm{Cl^-}\) can occur in HCl but does not produce the acidic behaviour. Exam tip: Blue litmus changing to red and \(\mathrm{H_2}\) evolution with a metal are key tests for an acid.
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.
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