Because there are 2 Cl on the left, we will put a coefficient 2in front of HCl on the right side to balance out the Cl. This would result in an unequal amount of H, with 6 on the right side and 7 in the left, so we have to put a coefficient of 2 in front of C6H5OH and C6H4OH on both sides to balance out the H. By doing this, we would obtain an equal amount of H on both sides. The Carbon is already balanced, and so is the Oxygen.
Solution;
The gas is at STP;
Where; T = 273 K , P = 1 atm
We know that 1 mole of a gas at STP occupies a volume of 22.4 liters .
V1/n1 = V2/n2
n2 = (V2/V1) n1
n2 = (2 l/22.4 l)(1 mole)
n2 = 0.0893 moles
But 1 mole of a compound has 6.022 × 10^23 molecules
Thus, number of molecules = 0.0893 moles × 6.022 ×10^23 molecules
= 5.378 × 10^22 molecules.
Answer is b..............…