# The mole and Avogadro constant...

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Thread starter 4 years ago
#1
Can someone please explain how to do this question, the data I have been given is is the mass of a proton, electron, and neutron and Avogadro's constant.
A) Calculate the mass of a 1H atom... I did 1/6.022*10^23?
B) Calculate the mass of a H+ ion... I did Avogadro's constant*1.6726*10^-24
C) Calculate the mass of one mole of 3H atoms... I did many internet searches but not an answer.
I WILL GIVE 10 VIRTUAL POINTS TO WHOEVER CAN HELP?!
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4 years ago
#2
(Original post by Wordnerd2)
Can someone please explain how to do this question, the data I have been given is is the mass of a proton, electron, and neutron and Avogadro's constant.
A) Calculate the mass of a 1H atom... I did 1/6.022*10^23?
B) Calculate the mass of a H+ ion... I did Avogadro's constant*1.6726*10^-24
C) Calculate the mass of one mole of 3H atoms... I did many internet searches but not an answer.
I WILL GIVE 10 VIRTUAL POINTS TO WHOEVER CAN HELP?!
I'll just pop this into the chemistry section for you! You're more likely to get some help there!

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4 years ago
#3
What does a 1H atom consist of?
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4 years ago
#4
mass = moles * molar mass

for a, moles = 1/Avg. Constant
molar mass = 1.00794 g since there is one proton (add mass of electron if given, but it won't affect if you take few significant figures)

do the same with other parts. H+ molar mass will be 1.00794 g
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4 years ago
#5
(Original post by Daniel Atieh)
mass = moles * molar mass

for a, moles = 1/Avg. Constant
molar mass = 1.00794 g since there is one proton (add mass of electron if given, but it won't affect if you take few significant figures)

do the same with other parts. H+ molar mass will be 1.00794 g
They don't ask for the molar mass of 1H or H+.

If you are given the mass of a proton, neutron and electron the best way to do the first two questions has nothing to do with moles. Only the third question makes you use Avogadro's number.
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4 years ago
#6
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4 years ago
#7
(Original post by alow)
They don't ask for the molar mass of 1H or H+.

If you are given the mass of a proton, neutron and electron the best way to do the first two questions has nothing to do with moles. Only the third question makes you use Avogadro's number.
yes, thanks for pointing that.

for some reason assumed masses as units of amu. Anyway, this make it a matter of adding masses and recognising the composition of each species.
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4 years ago
#8
(Original post by Daniel Atieh)
yes, thanks for pointing that.

for some reason assumed masses as units of amu. Anyway, this make it a matter of adding masses and recognising the composition of each species.
Yeah I agree, the exercise is probably to help them work out what a nucleus/atom/ion consists of.
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4 years ago
#9
(Original post by alow)
Yeah I agree, the exercise is probably to help them work out what a nucleus/atom/ion consists of.
yes exactly
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4 years ago
#10
(Original post by Wordnerd2)
Can someone please explain how to do this question, the data I have been given is is the mass of a proton, electron, and neutron and Avogadro's constant.
A) Calculate the mass of a 1H atom... I did 1/6.022*10^23?
B) Calculate the mass of a H+ ion... I did Avogadro's constant*1.6726*10^-24
C) Calculate the mass of one mole of 3H atoms... I did many internet searches but not an answer.
I WILL GIVE 10 VIRTUAL POINTS TO WHOEVER CAN HELP?!
A) A 1H atom consists of 1 proton and 1 electron. So just add the mass of 1 proton and 1 electron together, to get the mass of the atom as a whole.

B) A H+ ion consists of just a proton. So the mass of a H+ ion = the mass of 1 proton.

C) A 3H atom (tritium) consists of 1 proton, 2 neutrons and 1 electron. Add these together to get the mass of the atom. Then multiply this value by 6.022x10^23 to get the mass of 1 mole of 3H atoms.
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Thread starter 4 years ago
#11
Thank you so much! I now know how to do this !!

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4 years ago
#12
(Original post by lukemurp890)
A) A 1H atom consists of 1 proton and 1 electron. So just add the mass of 1 proton and 1 electron together, to get the mass of the atom as a whole.

B) A H+ ion consists of just a proton. So the mass of a H+ ion = the mass of 1 proton.

C) A 3H atom (tritium) consists of 1 proton, 2 neutrons and 1 electron. Add these together to get the mass of the atom. Then multiply this value by 6.022x10^23 to get the mass of 1 mole of 3H atoms.
I'm confused, wouldn't A and B just be 1g (as a whole number) and C be 3g?
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4 years ago
#13
(Original post by shohaib712)
I'm confused, wouldn't A and B just be 1g (as a whole number) and C be 3g?
Do you think an atom weighs 1g?
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4 years ago
#14
(Original post by alow)
Do you think an atom weighs 1g?
Oh sory I didn't ead the question properly - So would it be 1/avagados constant for A and B, and 3/avagados constant for C?
please correct me - so that I understand this topic properly 0
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4 years ago
#15
(Original post by shohaib712)
Oh sory I didn't ead the question properly - So would it be 1/avagados constant for A and B, and 3/avagados constant for C?
please correct me - so that I understand this topic properly Not quite.

It's easier to just add the masses of the required nucleons/electrons in A and B.

For C, it'll be about 3g.
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4 years ago
#16
(Original post by alow)
Not quite.

It's easier to just add the masses of the required nucleons/electrons in A and B.

For C, it'll be about 3g.
Oh so for A it would be 1.0005/Na nd B it would be 1/Na and C it would be 3.0005XNa (3.0005g)?

Why do we use the mass of the nutrons/electrons and protons rather than using the mass number? Is it because the mass numbeer only features the number of neutrons and protons?

Cant you write the masses as a rounded wholenumber (their mass number?) or does it have to be specific?

What are nucleons (is it neutrons and protons?)

Sorry for the bunch of questions 0
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4 years ago
#17
(Original post by shohaib712)
Oh so for A it would be 1.0005/Na nd B it would be 1/Na and C it would be 3.0005XNa (3.0005g)?

Why do we use the mass of the nutrons/electrons and protons rather than using the mass number? Is it because the mass numbeer only features the number of neutrons and protons?

Cant you write the masses as a rounded wholenumber (their mass number?) or does it have to be specific?

What are nucleons (is it neutrons and protons?)

Sorry for the bunch of questions The mass number of an element is the weighted average of its isotopes, by abundance. The question asks specifically for the mass of certain isotopes so you can't use the mass number. You must work it out using the masses of the constituent particles.

Also, you have to remember that the mass of a proton is not equal to the mass of a neutron, and neither are equal to the atomic mass unit.

Yes nucleons are neutrons or protons, i.e. the things that a nucleus is made of.
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4 years ago
#18
(Original post by alow)
The mass number of an element is the weighted average of its isotopes, by abundance. The question asks specifically for the mass of certain isotopes so you can't use the mass number. You must work it out using the masses of the constituent particles.

Also, you have to remember that the mass of a proton is not equal to the mass of a neutron, and neither are equal to the atomic mass unit.

Yes nucleons are neutrons or protons, i.e. the things that a nucleus is made of.
Isn't that for relative atomic mass? about the weighted average isotopes by abundance? (is RA the same as the mass number of an element?)

I see - so bassically you have to work out the relative isotopic mass?

Could you explain why the mass of a proton is not the same as a neutron? And why neither are not equal to u? (arent they both 1u each?)

Thank you so much for clearing up my questions - you are really helping me out a lot So was the answers to A,B and C correct then? (so I know I did it correctly?)
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4 years ago
#19
(Original post by alow)
The mass number of an element is the weighted average of its isotopes, by abundance. The question asks specifically for the mass of certain isotopes so you can't use the mass number. You must work it out using the masses of the constituent particles.

Also, you have to remember that the mass of a proton is not equal to the mass of a neutron, and neither are equal to the atomic mass unit.

Yes nucleons are neutrons or protons, i.e. the things that a nucleus is made of.
I think I get it:
If a question asked about the mass of an atom - we can use the Ar/Mass number?
but if it asks about a specific Isotope or ion - we have to calculate the mass individually but adding up the Relative masses of its subatomic paticles?
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4 years ago
#20
(Original post by shohaib712)
Isn't that for relative atomic mass? about the weighted average isotopes by abundance? (is RA the same as the mass number of an element?)

I see - so bassically you have to work out the relative isotopic mass?

Could you explain why the mass of a proton is not the same as a neutron? And why neither are not equal to u? (arent they both 1u each?)

Thank you so much for clearing up my questions - you are really helping me out a lot So was the answers to A,B and C correct then? (so I know I did it correctly?)
The mass number on a periodic table is the relative atomic mass.

Working out the actual mass of an isotope is quite difficult due to binding energy. Just add the mass of the constituent particles to get a decent approximation. Sometimes this is better than using 1amu for both, sometimes it isn't. Depends on the nucleus.

Neutrons are slightly heavier than protons. The amu is somewhere between them.

What I would do for 1H, is just add the mass of a proton and an electron.

For 1H+ just use proton mass.

For 1mol of 3H, use 3*amu + 1*electron mass, then multiply it by Avogadro's number.
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