Question

Copper oxide reacts with $HCl$ and gives:
A. Hydrogen
B. Water
C. Copper salts
D. Both B and C

Answer 1

Hint: Think about the nature of copper oxide and how it may react with acids and bases. Plot out the reaction that occurs and predict the reaction assuming that this is a double displacement reaction that produces a stable salt.

Complete step by step answer:
We know that copper oxide has the formula of $CuO$ is an amphoteric oxide. An amphoteric oxide is a compound that can act as both an acid or a base depending on the conditions and reagents present. These amphoteric oxides favour the formation of salts when reacted with both acids and bases. Metals usually form amphoteric oxides and hydroxides since they have multiple oxidation states that can accommodate bond formation with different reagents.
Since, $CuO$ is an amphoteric oxide that is reacting with $HCl$, it will act as a base and undergo a neutralization reaction to form salt and water. Now let us look at the reaction that actually occurs:

\[CuO+2HCl\to CuC{{l}_{2}}+{{H}_{2}}O\]

This is a double displacement reaction where chlorine ions replace the oxygen in the copper oxide and the oxygen combines with hydrogen atoms to form water. Thus, when copper oxide reacts with hydrochloric acid it forms a salt of copper along with water.
So, the correct answer is “Option D”.

Note:Amphoteric oxides can act as acids too. This happens as they have a lot of lone pairs of electrons which they can donate to form bonds. Copper in $CuO$ also does this to react with $NaOH$ to form a complex compound called the sodium tetra hydroxy cuprate(II). To act as an acid, copper has free orbitals that it can use to accept electron bond pairs.