Mass-Mass Chemistry Problem?
How many grams of sulfer dioxide are needed to react with 100.0 grams of oxygen gas according to the following UNBALANCED reaction...
SO2 + O2 ====> SO3
So I balanced the equation:
2SO2 + O2 ====> 2SO3
Now, My chemistry teacher (mind you, can't help anyone, she really sucks at teaching)
She gave us the answer to this question, which she says is 401 but I cannot come up with that answer.
I come up with the answer 25 grams or 100 grams.
CAN ANYONE HELP?
Comments
ok first off you start with dimensional analysis. Pretend like the lines are straight and not supposed to be dashed...
100.0g O2 l 1 mol O2 l 2 mol SO2 l 64.1g SO2
------------ ---l---------------l--------------l--------------l-----------
1 mol O2 l 32.0g O2 l 1 mol O2 l 1 mol SO2
100.0 g of O2. The molar mass of O2 is 32, so that goes on the bottom. There is 32 grams of O2 in 1 mole of O2. Then you do your molar ratio from the balanced equation. In the balanced equation, there is 1 mole of O2 and 2 moles of SO2. You want the moles of O2 to cancel out, so put it on the bottom and the 2 moles of SO2 on top. Then 1 mole of SO2 is equal to the molar mass of SO2 which is 64.1g. If you multiply everything on top then divide it by everything of the bottom, you will get 400.625. You only need 3 significant figures so it is rounded to 401 grams.
It seems that you are mixing the concepts of mass and moles. Your correct, balanced equation tells you that you need 2 moles of SO2 for each mole of O2 that reacts.
If you have 100 grams of O2, then you have 100/32 moles of O2 (30 is the formula weight of O2) = 3 moles.
Now from your balanced equation, you know that you need
2 * 3 moles of SO2 = 6 moles.
Now use your periodic table to find the formula weight of SO2. 32 + 16 + 16 = 64 gm/mole
64 gm/mo * 6 moles = 384 gm (when you use your calculator to do the math, you will probably be closer to 400)
That's easy,
in your balanced equation 100g of O2 / 32g /mole=3.125 moles.
Since you need 2 moles SO2 for every 1 O2
3.125* 2 moles =6.25 moles * ( molecular weight of SO2)64g=400g
see easy, my teachers suck too and i'm in University!
step#1 write equation(balanced) of the reaction.step#2 write molar mass of the given & required substance.step#3 using balanced equation find how much the required substance is produced from the given e.g 171g.(1 mole) Ba(OH)2 can be made by 153g.(1 mole) BaO. step#4 now calculate how much given substance will be required to produce 1g. of required substance e.g 153/171. step#5 finally calculate the amount of given substane required to produce the asked quantity by multiplying the asked value to the answer of step4 e.g (153/171)x18.