<p>Hey CCer's
Im a sophmore and I'm currently enrolled in basic chem. I'm having the toughest time right now and would really appreciate it if anyone had the time to explain molar calculations and conversions as well as molar mass, ect. Thanks in advance</p>
<p>I hated chemistry so much...except for balancing equations, lol.</p>
<p>molar mass you take the mass as listed in the periodic table of each element and then multiply it by the number of each element that you have. Then you add all the total masses for each type of element together.</p>
<p>To calculate how many moles a substance has, you divide the mass of the substance by its molar mass. (n = m/M; n is moles, m is mass, M is molar mass)</p>
<p>For example, let's say a question asks you to calculate the number of moles in 20g of H2O.
The molar mass of H2O is 2(1.01) + (16.00) = 18.02g/mol
Now, divide the mass by the molar mass.
20g/18.02g/mol = 1.1 mol</p>
<p>If the question then asks you how many moles of H there are in the substance, take the number of moles and multiply it by the number of H molecules.
(1.1mol)*2 = 2.2 mol of H</p>
<p>What types of conversions are you doing right now?</p>
<p>dimensional analysis is your friend ;)</p>
<p>oh ok! That makes tons more sense then what my textbook says. Thank you so much</p>
<p>w/e type of conversion it asks you to do, turn everything into (unit)/mol first, write down the units(including forumla names) for EVERYTHING to start with and problems'll be soo much if you can work with the units.</p>
<p>molar questions are quite fun once you get used to them, when I first learnt them I had the hardeset time too(and it wasnt the math that confused me), but chem gets better after this.</p>
<p>I dislike chemistry like crazy.</p>
<p>I hated it last year.. this year I think other than math chem is becoming my favorite subject. chem's actually a pretty easy thing, it doesn't have the amout of memorizing like bio, it doesnt have amount of concept/calculation like phys. its just.. chem!</p>
<p>ex. how many moles in 4.65 * 10^24
or molar mass of magnesium hydroxide Mg(OH)2
or convert 15 grams of lithium to moles</p>
<p>Chem is all conceptual. I have already taken AP Chem as well, made the AP test a breeze. </p>
<p>Hold out, it seems harder than it is!</p>
<p>Thanks for the encouragement :)</p>
<p>I agree with hornetguy; Chem seems hard, but pretty soon it's just going to "click" into place and it will be a breeze.</p>
<p>how many moles in 4.65 * 10^24
I'm assuming that's the number of particles in a substance. If it is, you would take that number and divide it by (6.02 X 10^23), or Avagadro's number. That will give you the number of moles.</p>
<p>That's because (number of moles)(Avagadro's number) = Number of particles in the substance.</p>
<p>molar mass of magnesium hydroxide Mg(OH)2
As a previous poster said, you would look on the periodic table for the mass for Mg, O, and H. (OH)2, as I'm sure you know, means there are two hydroxides in the compound.</p>
<p>convert 15 grams of lithium to moles
This uses the n=m/M formula explained earlier.</p>
<p>i LOVE chemistry.</p>