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Gotta be huge don't it?
George, What unit of measure equals a mole??? I have never heard that before???
Water has a molecular weight of 18 (with some approximation), which gives it a molar weight of 18 (i.e. that 18 grams of water contains approximately 6.022 x 1023 molecules).The density of water is 1 gram per cc, so 1 mole of water takes 18cc of volume.1 cup is approximately 250ml (i.e. 250cc) - so 1 cup will contain approximately 13.89 moles of water, which will contain approximately 8.36 x 1024 molecules of water.
Quote from: Karen W. on 17/01/2008 10:18:06 George, What unit of measure equals a mole??? I have never heard that before???The mole was a brilliant concept / invention.It works because, in a chemical reaction, the atoms of each element all have the same mass. Their masses are integral numbers of proton (or neutron) mass. Now a single atom of Oxygen has the mass of 16 atoms of Hydrogen.When combined with two Hydrogen atoms, the Water molecule ( H2O will have a mass of 16+1+1 = 18.That's obvious but you can't deal with individual molecules. But, if you take 16grams of Oxygen and 2grams of Hydrogen, they will react to produce exactly 18grams of water with nothing left over. This is if you take the reaction to completion.It's like taking boxes of leggo components and ending up with another box full of completed models, with no bits left over. This allows you to make pure substances by reacting known amounts of the component atoms, working in grams. Chemical factories deal in massive tanks of ingredients and use 'whole tanks' in their processes.The mole idea also allows you to work out what a substance consists of by weighing the amounts of some known substances which react with the unknown one - as long as you take the process to completion. One example of when you can tell if the reaction has been taken to completion is when you neutralise a base with an acid.They were starting to use these ideas at the time of Humphrey Davey and Lavoisier! Brilliant, don't you think?There is a teensy problem because not all atoms of all elements are identical in mass; different isotopes may occur with one neutron more or less than others (chemically the same but different atomic masses); naturally occurring Chlorine is a mixture of isotopes and its average atomic mass is 35.5. To deal with this you work with this average 'molar' mass and you get good answers.I've always said that Chemists need to get things in proportion!
I heard that Lightarrow. Thanks.What's the molar mass of carbon? It was just on our exam today and we didn't go over it at all and I was like wow. And I just guessed 1 since carbon is one AMU