Question

Zinc reacts with potassium hydroxide to form:
A. Zinc hydroxide
B. Zinc oxide
C. potassium zincate
D. all of the above

Answer 1

Hint Zinc is an element with symbol Zn and atomic number 30. It is an active metal belonging to group 12. Potassium hydroxide also known as caustic potash is an inorganic base with chemical formula $KOH$.

Complete answer
We know that, when a metal reacts with a base then a salt is formed along with evolution of hydrogen gas. This reaction between the metal and base can be expressed with the help of following expression;
\[Metal{\rm{ }} + {\rm{ }}Base \to {\rm{ }}Salt{\rm{ }} + {\rm{ }}hydrogen\]
The hydrogen gas evolved during the reaction can be detected with the pop sound as it burns when a burning candle is brought near the mouth of the test tube. Not all metals react with the bases. But such metals whose oxides are amphoteric in nature react with strong bases. Potassium hydroxide is a strong base / alkali. Potassium hydroxide or caustic potash is also used as raw material for the production of potassium. When potassium hydroxide reacts with amphoteric metal then the products formed are double and complex salts.
Also, zinc is an active metal with amphoteric nature. So zinc reacts with potassium hydroxide to form potassium zincate which is a salt. This chemical reaction can be explained with the help of following balanced chemical equation;
\[Zn{\rm{ }} + {\rm{ }}2KOH{\rm{ }} \to {K_2}Zn{O_2}{\rm{ }} + {\rm{ }}{H_2}\]
Zinc granules when heated with potassium hydroxide solution.

Hence, option (C) potassium zincate, is the correct option.

Note:
Thus, zinc metal upon reaction with potassium hydroxide forms a salt named potassium zincate along with evolution of hydrogen gas. This is due to the amphoteric nature of the zinc that it reacts with a strong alkali to produce double and complex salt.