Question

Four 1L flasks are separately filled with the gases hydrogen, helium, oxygen and oxygen at the same temp and pressure. The ratio of total no. of atoms of the gases present in the different flasks would be:
A. 2 : 1 : 2 : 3
B. 1 : 2 : 3 : 2
C. 4 : 1 : 2 : 1
D. None of these

Answer 1

Hint: The ratio of total no. of atoms can be found by the ideal gas equation, PV = n R T. The hydrogen, and oxygen as diatomic molecules, helium as monatomic, and helium as triatomic molecules.

Complete step by step answer:
1. We know, an ideal gas behaves in a manner that follows the equation PV = nRT, where P represents the pressure of gas, V volume of gas, n represents no. of moles, R is the gas constant, and T is the temperature constant.
2. As mentioned, the temperature and pressure are constant, and the volume of four flasks is constant equal to 1L.
3. Now, if P, V, and T are constant; therefore, the no. of moles are also constant.
Thus, the molar ratio of hydrogen, helium, oxygen, and ozone is 1:1:1:1 respectively.
4. We know that hydrogen, and oxygen has 2 atoms; helium has 1; ozone has 3 atoms.
Therefore, the ratio of the number of atoms of hydrogen, helium, oxygen, and ozone is 2:1:2:3 respectively. The correct option is A.

Note: Don’t get confused between the molar ratio of atoms and the ratio of number of atoms. The molar ratio relates to the number of moles, whereas the number of atoms relates to the atom unit present in an element like hydrogen is represented as H$_2$.