A kilogram of hydrogen is having more molecules.

Explanation:
For hydrogen that value is 1.008. For oxygen it’s 16.00. That means however many times you can divide the mass by its molar mass, So for example 1000g (1kg) / 1.008 is approximately992 moles of hydrogen. And 1000g/16.00 is 62.5 moles of Oxygen. Now to put it all together, one mole is equal to 6.02x10^23 molecules so obviously since there are more moles of hydrogen, you would have a significantly larger amount of hydrogen.

At Initial state

p_i = 1atm

T₀=-173^oc =100k

v_i=v

Finally

P_f= 2 atm

T_f = ?

V_f= v(constant)

By ideal gas law

PV = nRT

V = T/P = constant

T_i/p_i= T_f/p_f

T_f = T_i*P_f/p_i

=100*2/1

= 200k = -73^oc

The speed of molecules follows directly from measuring the pressure and density-you don’t need to know the size of molecules. In standard kinetic theory collisions with other molecules have always been ignored because the molecules were tiny. Though theyaren't. So the molecules are not going in straight line. Thus it takes time for the smell to spread in the room.