#### Answer

The number of H atoms in $C_{22}H_{?}ClN_{2}O_{2}$ (Loratadine) is 23.

#### Work Step by Step

$C_{22}H_{?}ClN_{2}O_{2}$ (Loratadine) has 12 degrees of unsaturation (4 rings and 8 double bonds).
The formula for the equivalent saturated hydrocarbon will be $C_{22}H_{46}$
Let the number of H atoms in $C_{22}H_{?}ClN_{2}O_{2}$ (Loratadine) be $x$.
We know that to the number of H atoms in the given compound,
(a) the number of halogen atoms present in the formula are added
(b) the number of nitrogen atoms are subtracted from, and
(c) the number of oxygen atoms are ignored
to get the equivalent formula of the unsaturated hydrocarbon.
In this case, it turns out to be $C_{22}H_{(x+1-2)}$ or $C_{22}H_{x-1}$
Now , since the degree of unsaturation can be found out by subtracting the number of hydrogen atoms in the equivalent hydrocarbon formula of the given unsaturated compound from that of the saturated compound, we have
$H_{46}-H_{x-1}=12H_{2} = H_{24}$, or
$H_{46}-H_{x-1}=H_{24}$
i.e. $H_{46}-H_{24}=H_{x-1}$
$H_{22}=H_{x-1}$ or
$H_{23}=H_{x}$
Thus $C_{22}H_{?}ClN_{2}O_{2}$ (Loratadine) has 23 H atoms.