Molar mass confusion :(

Roshniroxy

14

What is molar masses and avagardos number and how are they related. Really very very confused.

Thanks in advance !

OP

bump

There is avagardos number if atoms in a mole.

Reply 3

michaelhaych

15

Don't bump after 6 minutes.

Avagadro's Constant = 6.0225 x10 to the power 23. This is the number of atoms/molecules in 1 mole of any substance.

1 Molar Mass = Atomic/Molecular mass of a substance in grams. e.g. CO2: the molecular mass = 44 (1 Carbon = 12 & 2 Oxygen = 32). 1 Mole of CO2 = 44g.

So in 1 mole of CO2 (44g of CO2) there are 60.225 x 10 to the power 23 molecules of CO2.

(edited 12 years ago)

Reply 4

House1992

Molar mass is the mass per mole of a substance ,

eg Molar mass of Carbon is 12 = 12 grams
Molar mass of CO2 is 12+(16*2) = 44 grams

Avagardos number is the number of atoms per mole.

Amedeo Avogadro

or to be precise

Lorenzo Romano Amedeo Carlo Avogadro

Reply 6

Roshniroxy

OP

14

Original post by michaelhaych

Don't bump after 6 minutes.

Avagadro's Constant = 6.0225 x10 to the power 23. This is the number of atoms/molecules in 1 mole of any substance.

1 Molar Mass = Atomic/Molecular mass of a substance in grams. e.g. CO2: the molecular mass = 44 (1 Carbon = 12 & 2 Oxygen = 32). 1 Mole of CO2 = 44g.

So in 1 mole of CO2 (44g of CO2) there are 60.225 x 10 to the power 23 molecules of CO2.

Sorry I was doing homework and it's due in tomorrow.

why is it 60.225, how come you multiplied it by 10 ? :s

And how can there be a fixed number of molecules in each mole as all elements are different with different relative atomic masses ?

Reply 7

Dualcore

Though if we're being picky moles can be used for things other than atoms, they can be used for ions molecules and the like.

Reply 8

Coeusful

Original post by Roshniroxy

Sorry I was doing homework and it's due in tomorrow.

why is it 60.225, how come you multiplied it by 10 ? :s

He just made a small typo; it would still be 6.0225x10^23.

Reply 9

Roshniroxy

OP

14

Original post by House1992

Molar mass is the mass per mole of a substance ,

eg Molar mass of Carbon is 12 = 12 grams
Molar mass of CO2 is 12+(16*2) = 44 grams

Avagardos number is the number of atoms per mole.

how can their be the same number of atoms for different moles of different substances ?

Reply 10

Dualcore

It's not 60.225 it's 6.0225^23 it's a huge number. A mole isn't a measure of weight as such it's a measure of amount, a mole of carbon would weigh roughly 12g where as a mole of hydrogen weighs roughly 1g, but in both cases there is still the same number of molecules, if you reacted 1 mole of one substance and reacted it with a mole of another substance and the product needed a 1:1 ratio of the reactants you would recieve on mole of your product, it doesn't matter how heavy a mole of a substance is, it is purely a measure of amount.

Reply 11

Dualcore

Original post by Roshniroxy

how can their be the same number of atoms for different moles of different substances ?

That is the whole point of moles, in one mole there will always be the same number of atoms regardless of other factors such as weight.

Reply 12

michaelhaych

15

Original post by Roshniroxy

Sorry I was doing homework and it's due in tomorrow.

why is it 60.225, how come you multiplied it by 10 ? :s

And how can there be a fixed number of molecules in each mole as all elements are different with different relative atomic masses ?

It isn't multiplied by 10. That's just the number given in standard form. It's easier to write it as 6.0225 x 10^23 than to write 602250000000000000000000 every time.

A long time ago a very clever man named Avagadro worked out that that number tells you the number of times an atom of an element is heavier than 1/12 of Carbon-12.

You don't need to know why that specific number was chosen, it is simply a unit of measurement. Just like you don't need to know why there are 12 inches in 1 foot.

There is a fixed number because it is a unit of measurement. The different Relative Atomic Masses determine how heavy 1 mole is.

1 mole of Oxygen = 16g
1 mole of Nitrogen = 14g
1 mole of Seaborgium = 266g

1 dozen bricks will weigh more than 1 dozen feathers and have different properties even though they both contain 12 items.

You could do it the opposite way (how many molecules of a substance you need in order to obtain 1g of a substance) but it is much easier to use moles.

(edited 12 years ago)

Reply 13

House1992

Original post by Roshniroxy

how can their be the same number of atoms for different moles of different substances ?

If we take say carbon, sulfur, iron, copper and lead for instance. They all have different weights in grams,

Carbon = 12g
Sulfur = 32.1g
Iron = 55.8g
Copper = 63.5g
Lead 206.8g

but each one contains 6.02x 10^23 atoms or 1 mol of atoms

So its like saying for Carbon, 12g of carbon gives us 6.02x 10^23 atoms
Sulfur 32.1g also gives 6.02x 10^23 atoms or 1 mole of atoms

Reply 14

feesfees

Original post by Roshniroxy

What is molar masses and avagardos number and how are they related. Really very very confused.

Thanks in advance !

Ill explain Avogadro constant first.

It is just a number - 6.02 x 10^23 which explains the number of atoms or molecules in a given mole of something.

So basically, imaging you are one atom. If you multiply and multiply so that there are 6.02 x 10^23 of you, there would be one mole of you.

Now take the element Carbon. If there are 6.02 x 10^23 atoms of Carbon, it means there is 1 mole of Carbon.

So, if you take 5 atoms of Carbon, it would be so tiny that you cant see it. So what you do is you take a mole of Carbon. That is Carbon with 6.02 x 10^23 atoms in it. Now, this amount would be measurable as 6.02 x 10^23 atoms is a large number. So, the weight of one mole of this element (Carbon in this case) is called the molar mass.

PM me if you want to know other things. Ill try to help

See also: http://www.exo.net/~emuller/activities/What%20is%20a%20Mole.pdf

Molar mass confusion :(

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