How many grams of S8 are needed to produce 225 grams of sulfur hexafluoride? I know to begin with a balanced equation S8+24F2(arrow)8SF6. I've spent a couple of hours trying to figure out the next step, but I'm stuck. Thanks for any pointers!
By the way, my son first posted this question and received a message that it did not post. So in trying to help him, I reposted a similar question. Sorry for the double post of this problem. Thanks!
This a regular stoichiometry problem. Here are the steps; I suggest you print this out and keep it. This procedure will work any "simple" stoichiometry problem. It will work limiting reagent problems, also, but it needs two or three extra steps thrown in.
1. Writ and balance the equation. You've done that.
2. Convert grams of what you have (mols SF6 in this case) into mols. mols = grams/molar mass.
3. Using the coefficients in the balanced equation, convert mols of what you have (SF6) into mols of what you want. This way.
?mols SF6 x (1 mol S8/8 mols SF6) = ?mols SF6 x 1/8 = mols S8.
4. Now convert mols S8 to grams. That is grams S8 = mols S8 x molar mass S8.
Thanks for helping so quickly. For step 2 above, when converting grams to mols, is it 1.54, or am I completely missing something in this step? Thanks again!
1.54 mols for 225 g SF6 is correct. Go to the head of the class.
Thanks! But maybe not so fast.
For Step 3, I really feel lost. Where you've typed in SF6 above, are those the places I need to now plug in 1.54 that I've solved for?
So something like: 1.54 x (1 mol S8/8 mols 1.54) = 1.54 x 1/8 = mols S8 Or am I way off on this part now?
And thanks, too, for the idea of printing off the steps. That helps!
Maybe yes, maybe no. I can't tell exactly what you are asking so here is the problem is greater detail.
Step 1 is the equation.
Step 2 calculates the mols of what you have (you have 225 g SF6 to prepare) and you get that by mols = grams SF6/molar mass SF6 = 225/146 = 1.54 mols SF6 needed.
Step 3 converts mols of what you need (the 1.54 mols SF6 is what you need to prepare) to mols of what you want (you wantto know mols S8). You do that with the coefficients which I showed you but I'll do it again. The reason I wrote it out in my first response is that I wanted you to see that the units of mols SF6 cancel and you are left with mols S8. That's how you know which coefficient number to put in top and which goes on the bottom of the fraction. That fraction is 1/8 in this problem.
1.54 mols SF6 x (1 mol S8/8 mols SF6) = 1.54 mols x (1/8)= 0.1925 mols S8 that will be needed to prepare 1.54 mols SF6.
Step 4. Now that you know mols of what you want (mols S8) you convert mols S8 to grams S8.
g S8 = mols S8 x molar mass S8 = 0.1925 x 256 = 49.28 g S8 which rounds to 48.3 g to three significant figures.