Question

The black color of copper oxide turns _______ on treating with $HCl$.

• A. brown
• B. blue
• C. orange
• D. colourless

Answer 1

The correct option is B blue

When $HCl$ reacts with copper oxide, the black color of copper oxide turns blue due to the formation of its corresponding salt.

Water is formed along with salt. $CuC{l}_2$ solution is blue in colour.

$Cu+2HCl\to CuC{l}_2+H_{2}O$

Option B is correct.