O-Level Chemistry

[soseducation]

KSP2013777:

Somebody can help me to know my understanding correct or not?


Question - Is the number of atoms in 0.5 mol of oxygen gas and 0.5 mol of iron the same?

I think answer is not correct because Oxygen gas is made up of molecules (O2)

That means, 0.5 mol of oxygen gas have 0.5 x 2 x 6 x 10^23 = 6 x 10^23 oxygen atoms.

But, 0.5 mol of iron have 0.5 x 6 x 10^23 = 3 x 10^23 iron atoms.

So, answer is no, am I right? pls ans when u hv time.

Yes, you are right. The key word in the question is ATOMS. not molecules not ions. Oxygen itself is made up of two atoms since it is diatomic and you have to take that into consideration.

[KSP2013777]

soseducation, thanks. I so scared my answer is wrong

[soseducation]

KSP2013777:

soseducation, thanks. I so scared my answer is wrong

Don't worry. Be confident of yourself! :imcool:

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[KSP2013777]

What is the number of moles in 1.42g of chlorine gas? Because there are 2 chlorine atoms in 1 molecule, so 1.42 ÷ ( 2 × 35.5 ) = 0.02 mol

My understanding is correct or not?
Pls answer when u have time.
Tks

[hmong]

no of moles = mass/Mr


1.42 ÷ ( 2 × 35.5 ) = 0.02 mol of chlorine molecules

If they ask what are the number of moles of atoms then will need one more working.- multiply by 2.

[KSP2013777]

Thank you, hmong, for yr answer.

[KSP2013777]

Now I little bit worry. How u know answer they want is moles of chlorine molecules or moles of chlorine atoms. This question never say which one… so can give any one answer?

[KSP2013777]

How many atoms are there in 2 moles of ammonia gas?


My friend say 2 X 6 X 10^23 = 12 × 10^23 atoms

But I think must break up NH3 first

Hydrogen : 2 × 6 × 10 ^ 23 = 12 × 10 ^ 23 hydrogen atoms
Nitrogen : 2 × 3 × 6 × 10 ^ 23 = 36 × 10^23 nitrogen atoms
total atoms = 48 × 10^23 atoms

We argue long time about this. Who correct? My friend or I?

[Skyed]

Split. Your friend is correct if they ask number of molecules, not number of atoms.