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 Post subject: Can someone explain moles Chemistry?Posted: Thu Apr 10, 2014 4:47 am

Joined: Mon Oct 12, 2009 12:05 pm
Posts: 32
From simply what it means as moles from the beginning so what the hell is a mole ? and how it relates to concentration and why is concentration sometimes measuredin Mol Dm-3 what does it mean??!?!?? explain thoroughly please

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 Post subject: Can someone explain moles Chemistry?Posted: Wed Feb 22, 2017 5:56 am

Joined: Thu Apr 02, 2009 9:59 am
Posts: 1398
You first have to understand that the mole i a concept. Its generally used in chemistry and physic to measure mass, but it can also technically be used in other situation. It used to measure a quantity of "something". Anything. In science, a quantity of matter i literally synonymous to mas, and that why it used in place of a mas unity sometimes. In our situation, mol/dm^3 is used for concentration because concentration is defined a being a measure of mas divided by volume (assuming dm3 is already understood a being a measure of volume). A mole i defined a being equal to 6.022x10^23 unitie. From now on, we will refer to this ugly number a "Na" (dont get mixed up with sodium).

So, to recap, a mole is a given number of thing that can be used instead of a mass unity. Let get to examples. So lets say you have 10g of salt (NaCl) in 1l(or 1dm^3, 1l being equal to 1dm^3) of water. The cool thing about Na i that it can convert from Atomic Mass Unitie(or Molecular Mas Unities) to gram. Whats even cooler i that because thi number is so perfect, you dont need to make any calculation to convert. So in 1 mol of salt, you will have 58(23 for the sodium +35 for the chlorine) grams. Now since we know that there i 58g in 1 mol, how much mole will there be in 10g? I hope you answered around 0,172... if you didnt, heres the explanation. There are 58g of salt in 1 mole. You have only 10g. You have obviously les than 1 mole. In fact, you have 10 58ths of a mole. 10 divided by 58 equals 0.172413793. To solve your other problem, dont hesitate on adding me a a contact so you can ask question directly.

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 Post subject: Can someone explain moles Chemistry?Posted: Sat Jun 16, 2018 4:19 pm

Joined: Thu Apr 02, 2009 6:59 am
Posts: 1356
The mole is a convenient measure in chemistry, representing a fixed number of atoms or molecules. As it is related to the mass of the substance, properly moles should be referred to with a unit of mass, e.g. gram moles, kilogram moles or even tonne moles if you are a chemical engineer working with big quantities! But for general lab chemistry, gram moles are taken for granted.

So, taking approximate atomic weights (check out your data book!), one (gram) mole of Hydrogen is 1g, one mole of Carbon is 12g and so on. When you consider molecules and reactions, you can simplify the mass calculations by doing it all in moles... e.g. 1/2 mole of Oxygen (O2) plus 1 mole of Hydrogen (H2) gives you 1 mole of water (H2O).

Moles per cubic decimeter is simply how many moles of the substance can be found in 1 Dm3 of a solution. Again, using moles rather than plain weights makes it easier to calculate when dealing with reactions.

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