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HELP ! Chemestry question (I'm not sure of my answer)


hitmankratos
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Hi,

 

Okay. The question is how many moles are there in 2.107 * 10^24 water molecules.

Now I'd say something like 10 because the Avogadro Number is 2,022 * 10^23 and because 10^24 is a lot more then 10^23... But is there a precise way of doing this?

I know this question may seem a little bit stupid but sorry...Just started chemestry :D:D

 

Thanks in advance

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The unit that you have is "molecules." You want to get to moles. You have 6.022x10^23 molecules per mole. The reciprocal of this is 1/(6.022x10^23) mol/molecules.

 

So:

 

2.107x10^24 molecules * 1/(6.022x10^23) moles/molecules. Molecules cancel, and you are left with moles.

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A mole is a number. It's just a funny name for a very big number. I like to compare it to a dozen (12) and a gross (12x12 = 144). In the same way, a mole is 6.022*10^23 (note that the number in the opening post is not avogadro's number - there is an error there).

 

the question you need to solve here is similar as the question:

You have 27 apples, how many dozen of apples do you have?

A dozen is 12. You have 27/12 = 2.25 dozen.

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It's just a funny name for a very big number.

 

I agree with that. I recall a chemistry class in high school where we learning about the mole, and every student who attempted to read through the information for everyone to hear was unable to restrain from laughing when they said "mole".

 

 

...MOLE!:P

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Hi,

 

Okay. The question is how many moles are there in 2.107 * 10^24 water molecules.

Now I'd say something like 10 because the Avogadro Number is 2,022 * 10^23 and because 10^24 is a lot more then 10^23... But is there a precise way of doing this?

I know this question may seem a little bit stupid but sorry...Just started chemestry :D:D

 

Thanks in advance

 

A. The avogadro number/constant isn't 2.022 x 10^23 its 6.02 x 10^23 so please correct your facts.

 

b. you just have to divide the number by the avogadro constant to get the value.

 

c. And please don't use comma to denote a 'dot'. Its mathematically wrong.

 

Good luck and Welcome to the world of chemistry.;)

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c. And please don't use comma to denote a 'dot'. Its mathematically wrong.

 

Good luck and Welcome to the world of chemistry.;)

 

In many countries the comma is used for decimals, and the dot is used at the thousand, million, billion positions... There are actually two systems. It's totally retarded that this exists, and it's utterly stupid (typical Microsoft) that if you have for example a Dutch computer and Excel refuses to make decimals if you push the . on the keypad. But it's only wrong in English speaking countries (and perhaps some more that I am not aware of).

 

Chemistry rules! :D

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The use of commas and dots is a matter of convention, and there are two conventions. Mathematically, the dot is used to denote scaler multiplication and the stop is generally used to indicate decimals but there's a fair argument that it should be a dot too. (one's further up than the other and you only usually get the stop on a keyboard.)

 

On a related note, Avogadro has a capital A and "it's" has an apostrophe.

None of this makes any difference to the chemistry (not chemestry).

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yes the dot usually meeans(in english speaking countries) that theres a digit or a series of digits smaller than one if there behind the "." such as in 3.456 first one whould be a

^ ^

whole number were as the later one would be a number smaller than one. also this seams to be more of a mathamitics/chemistry question. mostly

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Thanks for your answers everyone...very helpful.

For the dot vs comma, I know about that already, the thing is that I go to a french school (so everything I study is in French), and when I was translating the problem in English, I wrote it in commas... :o)

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