In which of the following reactions,hydrogen is liberated?
$(i)$ $Al_{(s)} + HCl_{(aq)} \rightarrow$
$(ii)$ $Al_{(s)} + NaOH_{(aq)} \rightarrow$
$(iii)$ $NaBH_4 + I_2 \rightarrow$

$CuSO_4$ solution $+$ lime is called

Sea divers use a mixture of

$H_2C_2O_4 \xrightarrow{\Delta } \text{gas } (A) + \text{gas } (B) + \text{liquid } (C)$.
$\text{Gas } (A) \text{ burns with a blue flame and is oxidised to gas } (B)$.
$\text{Gas } (A) + Cl_2 \to (D) \xrightarrow{NH_3, \Delta } (E)$.
$A, B, C \text{ and } E \text{ are}$

Oxalic acid reacts with concentrated $H_2SO_4$ to produce a mixture of two gases. When this mixture is passed through caustic potash,one of the gases is absorbed. Which substance is formed by the absorption of the gas in caustic potash?

Consider the following statements:
$I$. Atomic hydrogen is obtained by passing an electric arc through hydrogen gas.
$II$. Hydrogen gas does not reduce heated aluminum oxide.
$III$. Finely divided palladium absorbs a large volume of hydrogen gas.
$IV$. Pure nascent hydrogen is obtained by the reaction of $Na$ with $C_2H_5OH$.
Which of the above statements are correct?