Chemiosmotic theory of $ATP$ synthesis in mitochondrion is based on

The energy of a photon is $3 \times 10^{-12} \ erg$. What is its wavelength in $nm$?
$(h = 6.62 \times 10^{-27} \ erg \cdot s; c = 3 \times 10^{10} \ cm/s)$

$x$ grams of calcium carbonate was completely burnt in air. The weight of the solid residue formed is $28 \text{ g}$. What is the value of $x$ (in grams)?

Consider the following reactions:
$C_2H_2 \xrightarrow[500^{\circ}C]{\text{red hot iron tube}} A$
$A \xrightarrow[70^{\circ}C]{\text{conc. } HNO_3, \text{conc. } H_2SO_4} B$
$B \xrightarrow{LiAlH_4} C_6H_5-N=N-C_6H_5$
$A$ and $B$ are:

At a certain place,a magnet makes $30$ oscillations per minute. At another place where the magnetic field is double,its time period will be:

The synthesis of crotonaldehyde from acetaldehyde is an example of $.......$ reaction.