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# Setting the understanding of a mole in concrete watch

1. Need some help with this question please, part b ...

1. Consider sugar lumps to be cubes of side 1cm. Suppose tat 1 mol of sugar lumps were laid on all the land on the Earths surface. The Earth's land surface is approximately 150 000 000 km^2.

a) Calculate the area of the Earths land surface in cm^2, 100,000 centimeters in a kilometer, so 150,000,000 x 100,000 = 150,000,000,000,000.
b) Taking Avogadros number to be 6x10^23, work out how many sugar lumps would be required. (For those of you who dont get it... i've checked and this is exactly how its written...)
2. 2. A hydrogen atom consists of 1 proton and 1 electron. The mass of a proton is 1.672648586x10^-27kg, electron mass is 0.910953448x10^-30kg.

Whats the mass of 1 mole of hydrogen?

I dont have a calc with me which can do standard form, but is the answer just 6x10^23 * proton mass, * electron mass?

Ok - The reply someone gave has just disappeared....
3. (Original post by LearningMath)
1. Consider sugar lumps to be cubes of side 1cm. Suppose tat 1 mol of sugar lumps were laid on all the land on the Earths surface. The Earth's land surface is approximately 150 000 000 km^2.

a) Calculate the area of the Earths land surface in cm^2, 100,000 centimeters in a kilometer, so 150,000,000 x 100,000 = 15,000,000,000,000
b) Taking Avogadros number to be 6x10^23, work out how many sugar lumps would be required.
sorry, sugar lumps required for what? 1 mol of sugar lumps? then thats just 6x10^23 lumps. Do you mean 6x10^23/1.5x10^13 = 4x10^10 full earths of sugar lumps for 1 mol?

(Original post by LearningMath)
2. A hydrogen atom consists of 1 proton and 1 electron. The mass of a proton is 1.672648586x10^-27kg, electron mass is 0.910953448x10^-30kg.

I dont have a calc with me which can do standard form, but is the answer just 6x10^23 * proton mass, * electron mass?
well whats the question lol - mass of 1 mole of hydrogen atoms? then 6x10^23 x (mass of proton + mass of electron) x 1000 = 1.004g
4. neither of these questions make sense rofl. You must be missing part of the question 1, and all of the actual question 2.
5. (Original post by EierVonSatan)
sorry, sugar lumps required for what? 1 mol of sugar lumps? then thats just 6x10^23 lumps. Do you mean 6x10^23/1.5x10^13 = 4x10^10 full earths of sugar lumps for 1 mol?

well whats the question lol - mass of 1 mole of hydrogen atoms? then 6x10^23 x (mass of proton + mass of electron) x 1000 = 1.004g
Ups my bad, havnt written it out fully or correctly, but you've interpreted it correctly These questions were supposed to help me understand, still dont quite understand what a mole is properly. Sometimes it appears to be a precise measurement, but its not, and then sometimes it appears to be a unit of something, which can be anything

Why does one mole of oxygen have a mass of 16g? All i can see is the textbook taking the atomic mass and slapping and grams unit behind it Could ya write out the calculation for why 1 mole of oxygen has a mass of 16g, maybe then il understand it better Thanks, and hopefully this post is better written!
6. @ originalname Well thats kind what i thought, seems abt obvious - So why put in 6x10^23 .... also if it was as you say, what relation to chemistry would it have! lol EEEEK STOP DELETING POSTS! lol this doesnt make sense to people viewing it if ya keep deleting, nothing wrong with being wrong, these questions are strange..
7. Why not rewrite the full question out?
8. Those questions are bloody crap lol!

The defintion of a mole, is the number of atoms in exactly 12g of carbon-12. This turns out to be 6.022 x 10^23 atoms.

Each element as an "atomic mass" or Mr, given in grams per mol.

So, if you have 24g of carbon-12... we can see from the table that carbon-12 has an mr of 12 g per mol... 24/12 = 2, so there must be 2 mols in our sample.

This equates to 2 x 6.022 x 10^23 atoms.

One mole of oxygen has a mass of 16g because It's Mr is 16g per mol... I.e. 6.022 x 10^23 atoms of Oxygen weighs 16g. That's just how it is.
9. If you start setting moles in concrete, the RSPCA will be on to you in a flash. (Trust me.)
10. 1 mole of Oxygen is the atomic mass of oxygen measured out in grams.

The atomic mass of Oxygen is 16. So, if you measure out 16g of oxygen, you have one mole of Oxygen. And it just so happens that 1 mole of oxygen, and of any element, contains 6x10^23 atoms.

Relationship:

Mass = moles x atomic mass of element.

This makes sense if you think about it because rearranged: moles = mass / atomic mass. As one mole is atomic mass in grams, then 16g of oxygen divided by 16, which is its atomic mass, will give 1.
11. As for question 2...

A hydrogen atom is comprised of one proton and one electron...

A mole of hydrogen is 6.02 x 10^23 hydrogen atoms.

So one mole of hydrogen weighs 6.02 x 10^23 x (1.672648586x10^-24 + 0.910953448x10^-27) <- had to convert the kg to g.

Some calculations later... equals 1.

1.00781 g per mol. Looking at the periodic table, the Mr of Hydrogen is 1.01 g per mol, so yes.
12. (Original post by LearningMath)
Ups my bad, havnt written it out fully or correctly, but you've interpreted it correctly These questions were supposed to help me understand, still dont quite understand what a mole is properly. Sometimes it appears to be a precise measurement, but its not, and then sometimes it appears to be a unit of something, which can be anything

Why does one mole of oxygen have a mass of 16g? All i can see is the textbook taking the atomic mass and slapping and grams unit behind it Could ya write out the calculation for why 1 mole of oxygen has a mass of 16g, maybe then il understand it better Thanks, and hopefully this post is better written!
Okay the mole is is the unit that we use to determine amount in a similar way that we use kg for mass and seconds for time. A mole of X is 6.022x10^23 amounts (e.g. atoms or molecules) of X (e.g. cars, drunks, bromine etc).

So because the mass of an atom is mostly made up of protons and neutrons then the mass number of the atom = 1 mole of atoms in grams. A mole of oxygen atoms therefore 16g, a mole of oxygen molecules (O2) is 32g.
13. (Original post by DaveJ)
1 mole of Oxygen is the atomic mass of oxygen measured out in grams.

The atomic mass of Oxygen is 16. So, if you measure out 16g of oxygen, you have one mole of Oxygen. And it just so happens that 1 mole of oxygen, and of any element, contains 6x10^23 atoms.

Relationship:

Mass = moles x atomic mass of element.

This makes sense if you think about it because rearranged: moles = mass / atomic mass. As one mole is atomic mass in grams, then 16g of oxygen divided by 16, which is its atomic mass, will give 1.
AHA, thats cleared it up, i tried thinking like that, but thought 6x10^23 was PARTICLES, which i thought could refer to proton and neutrons, which obviously have the same mass! Reckon i've got this effing mole, dont understand the questions still, but going by the responses im not sure they are really helpful, so il skip em Thanks for you help + sarcy mole comment we all knew was coming!
14. We could do the same to work out why 1 mol of Oxygen = 16g.

You need to know the mass of a neutron though.

1.6749 x 10^(-24) g

So, 8p 8e 8n.

6.02 x 10^23 x ((1.672648586x10^-24 x 8) + (0.910953448x10^-27 x 8) + (1.6749 x 10^-24 x 8)) = 16.

voila.
15. (Original post by originalname)
We could do the same to work out why 1 mol of Oxygen = 16g.

You need to know the mass of a neutron though.

1.6749 x 10^(-24) g

So, 8p 8e 8n.

6.02 x 10^23 x ((1.672648586x10^-24 x 8) + (0.910953448x10^-27 x 8) + (1.6749 x 10^-24 x 8)) = 16.

voila.
Lol that looks quite helpful actually, but can you explain what all those standard form numbers are?!

EDIT: see it now anyways
16. (Original post by DaveJ)
Lol that looks quite helpful actually, but can you explain what all those standard form numbers are?!
one is the mass of a proton, the other of an electron

EDIT: I'm screenshoting all these threads lol, good notes, anyone else have trouble with moles for the first time? Just seem tricky to get ya head around...
17. (Original post by LearningMath)
one is the mass of a proton, the other of an electron
yeah see it now, didn't see the 8p 8n 8e above it at first.
18. (Original post by LearningMath)
proton and neutrons, which obviously have the same mass!
Well, no they don't :P

I'm off now anyways, good luck! I assume you're at the start of sixth form, and the inital jump into AS chemistry through moles I found quite tricky at the start, but It's very easy when you get a good grasp on it.

All you need to know...

1 mol = 6.02 x 10^23 atoms.

The mole is defined as the number of atoms in 12g of carbon-12.

The equations

moles = grams / ram, for solids.

moles = concentration (in mol per dm^3) x volume (in dm^3), for liquids.

moles = volume (in dm^3) / 24, for perfect gases.

There are 1000cm^3 in 1dm^3. That's a useful conversion... good luck!

(Original post by LearningMath)
moles for the first time?
Defo. First thing we did... hardest thing I did in the whole 2 year course. It's just nothing like GCSE, and once you get adjusted everything starts to become easier.
19. (Original post by originalname)
Well, no they don't :P

I'm off now anyways, good luck! I assume you're at the start of sixth form, and the inital jump into AS chemistry through moles I found quite tricky at the start, but It's very easy when you get a good grasp on it.

All you need to know...

1 mol = 6.02 x 10^23 atoms.

The mole is defined as the number of atoms in 12g of carbon-12.

The equations

moles = grams / ram, for solids.

moles = concentration (in mol per dm^3) x volume (in dm^3), for liquids.

moles = volume (in dm^3) / 24, for perfect gases.

There are 1000cm^3 in 1dm^3. That's a useful conversion... good luck!

Defo. First thing we did... hardest thing I did in the whole 2 year course. It's just nothing like GCSE, and once you get adjusted everything starts to become easier.
Got relative and grams mixed up, thanks for ya help, rep ya and some others when i can, cya
20. (Original post by LearningMath)
Got relative and grams mixed up, thanks for ya help, rep ya and some others when i can, cya
Wait lol, surely if their relative masses are both 1, their actual mass in grams must be equal? (By equal, I mean pretty close to equal, not the EXACT same as.)

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