# Calculate the number of molecules of O2 when given the number of moles

• Chemistry

## Homework Statement

After balancing an equation, there are 1.82 moles of O2.

Calculate the number of molecules of O2. given moles.

## The Attempt at a Solution

in every O2 molecule, there are 2 moles of O.
so if the number of moles of O2 molecule is 1.82. then 1.82*2= 3.65 moles.

number of molecules= 3.65*6.022*10^23= 2.19*10^24.
Correct?

mfb
Mentor
in every O2 molecule, there are 2 moles of O.
In every single molecule?
number of molecules= 3.65*6.022*10^23= 2.19*10^24.
Correct?
That is the number of oxygen atoms. The question asked about the number of O2 molecules.

In every single molecule?That is the number of oxygen atoms. The question asked about the number of O2 molecules.
Oh.. so the number of molecules is just no. of moles times molar mass?
no need to multiply by 2?

Borek
Mentor
Oh.. so the number of molecules is just no. of moles times molar mass?

Number of moles times molar mass is a sample mass.

Think about a mole as of an overgrown dozen, with 6.02×1023 objects instead of 12. You have two dozens of molecules - how many molecules? You have two moles of molecules - how many molecules?

Number of moles times molar mass is a sample mass.

Think about a mole as of an overgrown dozen, with 6.02×1023 objects instead of 12. You have two dozens of molecules - how many molecules? You have two moles of molecules - how many molecules?
2*6.02×1023

the question included no of moles

mfb
Mentor
Oh.. so the number of molecules is just no. of moles times molar mass?
no need to multiply by 2?
Right.

epenguin
Homework Helper
Gold Member
Maybe you have go the question confused with the other possible similar kind of questions.
Forget everything you know about oxygen - it's irrelevant here.
Calculate the number of molecules of anything in 1.82 moles of that thing.
Is the same for anything.

Borek
Mentor
Right.

Beware: part of the OP answer was plainly wrong.