How many moles of oxygen (o2) are present in 33.6 l of the gas at 1 atm and 0°c?
a: 1.5
b: 2
c: 22.4
d: 32

The condition at 1 atm and 0°C is considered "Standard Temperature and Pressure" (a.k.a STP). At STP, all gases have an approximate volume of 22.4 L/ 1 mol.

33.6 L* (1 mol/ 22.4 L)= 1.5 mol.
(Note that the unit cancels out so you get the answer)

The correct answer is A. 1.5~

Acovalent bond is formed between the two hydrogen bonds

You use the atomic number to find out how many protons and neutrons there are in the atom. you use the atomic mass to find out how many protons and electrons there are in the atom.