Question
When a substance $$A$$ reacts with water it produces a combustible gas $$B$$ and a solution of substance $$C$$ in water. When another substance $$D$$ reacts with this solution of $$C,$$ it also produces the same gas $$B$$ on warming but $$D$$ can produce gas $$B$$ on reaction with dilute sulphuric acid at room temperature. $$A$$ imparts a deep golden yellow colour to a smokeless flame of Bunsen burner. $$A, B, C$$ and $$D$$ respectively are
A.
$$Na,{H_2},NaOH,Zn$$
B.
$$K,{H_2},KOH,Al$$
C.
$$Ca,{H_2},Ca{\left( {OH} \right)_2},Sn$$
D.
$$Ca{C_2},{C_2}{H_2},Ca{\left( {OH} \right)_2},Fe$$
Answer :
$$Na,{H_2},NaOH,Zn$$
Solution :
$$\eqalign{
& \mathop {2Na}\limits_{'A'} + 2{H_2}O \to 2\mathop {NaOH}\limits_{'C'} + \mathop {{H_2}}\limits_{'B'} \uparrow \cr
& \mathop {Zn}\limits_{'D'} + 2\mathop {NaOH}\limits_{'C'} \to N{a_2}Zn{O_2} + \mathop {{H_2}}\limits_{'B'} \uparrow \cr
& \mathop {Zn}\limits_{'D'} + dil.\,{H_2}S{O_4} \to ZnS{O_4} + \mathop {{H_2}}\limits_{'B'} \uparrow \cr} $$
$$Na$$ produces golden yellow colour with smokeless flame of Bunsen burner.