calculate the mass of 1 molecule of of oxygen gas : given [at mass of o = 16u,N_A =6.022 * 10²³ mol ^-1]

We are given that the atomic mass of oxygen is 16u. In a molecule of oxygen, there are two oxygen atoms and it is denoted by O₂. So, the molecular mass of O₂ will be 2 X 16u = 32u. Thus, the molar mass that is the mass of 6.023 X 10²³ molecules of oxygen will be 32g. So

mass of 6.023 X 10²³ molecules (one mole) of oxygen = 32g

mass of one molecule of oxygen = [32 / (6.023 X 10²³) ]g 

= 5.313 X 10^-23g

Thus, the mass of one oxygen molecule will be 5.313 X 10^-23g