Sure.
M stands for molar or moles per liter.
A mole is literally 6.02 x 10^23 individual somethings. Could be atoms, ions, molecules, or even actual mole animals that dig in the ground. lol
A mole is a unit of measure scientists like because it connects the microscopic world of atoms to real world weights and measures.
The ultimate definition arises by defining one mole of the carbon-12 isotope of carbon actually weighing 12 grams. That number, called Avagadro's number, is 6.02 x 10^23. A huge number that would be ridiculous for ordinary use.
How many chloride ions are in seawater? If folks went around saying 3 x 10^23 per liter, that gets cumbersome fast. But if someone says 0.5 moles per liter, or M, that's much easier to do calculations, etc.
Molar is a far better unit for scientists to use than is grams or mg or whatever when talking about ions interacting. 1 mole of sodium always combines with 1 mole of chloride to make sodium chloride. But since sodium and chloride weigh different amounts, the weight based interactions are never 1:1 and are always more complicated.
So back to acids. 1 M HCl means one mole of HCl per liter. Since the molecular weight of HCl is 36.5 grams per mole, 1 M HCl means 36.5 gramds of HCl per liter. FWIW, the 36.5 is not an integer because there are several isotopes of chlorine, each with its own integer (or close to integer) molecular weight, that are present in ordinary HCl.
OK, so then 0.1 M means 3.65 g HCL/L.
N is a different, and even more useful number in some contexts. It stands for Normal. It can apply to a number of different things, but in the case of an acid or base, it means how much acid (or base) is present.
For HCl, where there is exactly 1 H+ that comes from one HCL, then 1 M = 1 N.
But for other acids, we may get more than 1 h+ from one molecule.
Sulfuric acid is H2SO4. It is a very strong acid and both H come off:
H2SO4 --> 2H+ + SO4--
Thus, 1 M Sulfuric acids is 2 N.
In reality one could say that 1 M H+ always equals 1 N, and thus N in this case is an exact measure of the acid present, regardless of how it was made.
1M HCl = 0.5 M H2SO4 = 1 N
For doing alk titrations, some folks may use HCl, and some may use sulfuric acid, and if the concentration is always given as N, then it doesn't matter which is used.
Hope thqt makes sense.
