[devvaibhav]

Q:- If a mole were to contain 1 x 10²⁴ particles, what would be the mass of
(i) one mole of oxygen, and (ii) a single oxygen molecule?

My attempt:-
Mass of 6.023 x 10²³ molecules of O = 32g
Mass of 10²⁵ molecules of O = 32*10²⁵/6.023 x 10²³
And similarly for the second option.
Is this right?

Books' answer:-
Mass of 1 mole of O₂ is its molecular weight in g, i.e. 32g. (Isn't that wrong)

[Borek]

What is the mole definition?

[devvaibhav]

A mole is a quantity which contains as many particles/entities as there are atoms in 12 grams of pure carbon-12 equal to avogadro's constant which is 6.023 x 10²³.

Is the question just to confuse students? Because a mole is constant everywhere(of course)...

[Borek]

Question can be a little bit confusing, but applying mole definition as you listed you will get the answer your book gives.

Mole is not "a constant". It is defined using an arbitrary mass unit (gram). Ratio of molar masses of different substances doesn't depend on the mass unit, but actual number of objects (atoms, molecules) in a mole does.

[billnotgatez]

Is not the question saying

let us define a mole to be xxx

rather than 6.023 x 10²³

I hate this kind of question because in its attempt to make you understand the concept, but at the same time it undermines the memory of something.

[fledarmus]

This appears to be an attempt to make a thought question based on the historical derivation of the mole concept. Moles were originally identified as molar ratios, and since nobody knew how big an atom actually was, the rather general definition that you gave in your response was used -

A mole is a quantity which contains as many particles/entities as there are atoms in 12 grams of pure carbon-12

Regardless of what the later determination of the actual number of atoms, the ratios still hold. If one mole of particles of pure carbon 12 give 12 grams of material, then one mole of molecules of oxygen will give 32 grams, and one mole of atoms of oxygen will give 16 grams (approximately). The mole was not originally defined in terms of numbers of particles, it was defined in terms of the mass of that number of particles, so what the actual number turned out to be was irrelevant to the definition. It took almost 100 years after Avogadro proposed that there should be such a constant for Perrin to calculate what the number was.

All that being said, I think it is a poorly written question and requires you to read the mind of your instructor to get the right answer.

[devvaibhav]

Well
Does anyone knows how was this quantity determined as i don't know how and i was not told how and it is not written how in Higher School Books?

[billnotgatez]

The below link discusses Mole
http://en.wikipedia.org/wiki/Mole_%28unit%29

We have already discussed the question given you

[rajajidwivedi]

nice question and you are going right