00:01
Alright, so assume that we're writing our name on a chalkboard and we want to determine how many chalk molecules it required.
00:07
So first it's useful to know that chalk is a compound, a chemical species that is made of calcium carbonate caco3, and this has a molar mass of a hundred point nine grams per mole, which we'll need later.
00:26
So if you measure the mass of the chalk on a simple like classroom balance before you go ahead and write your name and then you do the same thing after, the mass of chalk that's used is going to be equal to the difference if you take, well yeah, if you subtract the value before minus the value after, because by the law of conservation of mass all that's changed in the physical processes, you know, you put the chalk on the board so whatever's left is going to be the remaining mass.
01:11
So then this will give you the mass of the chalk that was used in grams or whatever unit, and then if you want to go in to convert to molecules, you'd need to convert from mass to moles first using molar mass as a conversion factor, which we have here for calcium carbonate is a hundred point nine grams per mole, and then you'd go from moles to molecules using avogadro's number as a conversion factor.
01:48
We know that there's six point oh two times ten to the twenty -third molecules in every mole...