Question

A soft metal $\left(A\right)$ gives violet flame test. When burnt ill excess $O_2$ ,$\left(A\right)$ gives chrome yellow powder $\left(B\right)$ which on reaction with water gives alkaline solution $\left(C\right)$ and $O_2$. Identify $A$ and $B$.

• A. $Na,N{a}_2{O}_2$
• B. $K,K_2{O}_{2}Z$
• C. $K,K{O}_2$
• D. $Li,L{i}_2{O}_2$

Answer 1

Answer: (C)

$K,K{O}_2$

Potassium gives violet flame test. So '$A$' is $K$

$K+excess{O}_2\to K{O}_2$

$K{O}_2+H_{2}O\to 4KOH+3O_2$

Therefore '$A$' is $K$ and '$B$' is $K{O}_2$