Would someone be able to help me understand how to find the molar mass of copper II sulfate, anhydrous form? Thank yall.

Question

jfraser · Answer

what's the formula for copper (II) sulfate?

anonymous · Answer

CuSO4?

jfraser · Answer

it is, now what's the molar mass of copper?

anonymous · Answer

Im not sure, I have a lot of troubles understanding molar mass

jfraser · Answer

grab a periodic table and look it up. you don't have to memorize any masses, because the periodic table has them all

anonymous · Answer

ok so it would be 159.5. sorry it took so long, my laptop died.

anonymous · Answer

159.5 g/mol? Is that what goes after?

anonymous · Answer

So is this my answer? What about when it is in the anhydrous form? I am not sure what that means but is there more to it? For some reason I thought my teacher said that there was more to it.

jfraser · Answer

in the anhydrous form, a salt has no water attached to it, so its molar mass is the sum of all the individual masses. In this case, $CuSO_4$ has (63.5g + 32g + 4(16g)) = 159.5g so you are correct.

If it were in its $hydrated$ form, you would have a certain number of water molecules attached after the formula of the salt, which would add to the molar mass

anonymous · Answer

awesome, thank you very much. I think that is where i have trouble, the hydrated form

jfraser · Answer

the only difference between hydrated and anhydrous is the presence of water. Each kind of salt can hold onto a different number of water molecules, which the formula will tell you. For example

$MgSO_4*7H_2O$ is magnesium sulfate $hepta$hydrate, because 7 water molecules are loosely held by the salt. The molar mass of the hydrate will be equal to the mass of $everything$ in the formula, including the water molecules

(24.3g + 32g+ 4(16g)) + (7x(18g)) = 246.2g/mol for the $hydrated$ magnesium sulfate

anonymous · Answer

But it wont always be 7H2O right? Depending on what it is.

jfraser · Answer

right. each salt will have its own number of waters, but the formula will tell you every time

anonymous · Answer

So it would be given for how much water is in it? Or i will just have to research what it is for that compound?

jfraser · Answer

it would depend on the problem

anonymous · Answer

Ok thank you very much for your help! :) I will PM you if i come across something else like this that i need help on. Also for just H20, the molar mass would be 18 g/mol, correct?

jfraser · Answer

yes

anonymous · Answer

Awesome thanks again. Have a great rest of the day Fraser!:)

jfraser · Answer

YW