Question

When hydrogen is passed over a black solid compound $A$, the products are a colorless liquid and reddish-brown metal $B$.
Substance $B$ is divided into two parts, each placed in separated test tubes.
Dilute $HCl$ is added to one part of substance $B$ and dilute $HN{O}_3$ to the other.
Write an equation for the reaction between hydrogen and substance $A$.

Answer 1

$CuO+H_2\stackrel{\Delta }{\to }Cu+H_{2}O$

Here the black compound is $CuO$ = A and the reddish-brown metal is $Cu$ = B