[kikienders]

How many grams of oxygen can be produced by decomposing 100.0g of BaO2 to BaO and O2? This is how I have started the problem. Am I doing this right? 2Bao2 yields 2BaO + O2
100.0g of BaO2 x 1 mol O2 x 1 mol O2 x 32g O2
__________________________________________ = 9.45g O2 produced

169.3g BaO2 2 mol BaO2 1 mol O2

H2SO4 + NaCl yields HCl + Na2SO4 what mass of H2SO4 is needed to react completely with 15.0 g of NaCl? H2SO4 + 2NaCl yields 2Hcl + Na SO4

15.0g of NaCl x 1mol NaCl x 1 mol H2SO4 x 98.1g H2SO4
_________ _____________ _____________ = 12.6g of H2SO4

58.5g NaCl 2 mol NaCl 1 mol H2SO4

Al + Cl2 yields AlCl3 25.0g of Al are reacted with 60.0g of Cl2. Which is the limiting agent? How much AlCl3 is produced? 2Al + 3Cl yields 2 AlCl3

60g of Cl2 x 1 mol x 1 mol AlCl3 = .85g AlCl3
________ ___________

71g Cl2 1 mol Cl2


25.0g Al x 1 mol x 1 mol AlCl3
_________ ____________ = .93g

27g of Al 1 mol Al

limiting reagent is Cl2

.85 mol of AlCl3 x 2 mol Al x 133.5g AlCl3

______________ _______________ = 23 excess Al

2 mol AlCl3 1 mol


.85 mol AlCl3 x 3 mol Cl2 x 71g Cl2

________________ ____________ = 90.53 excess Cl2

2 mol AlCl3 1 mol



KI + H2SO4 yields I2 + K2SO4 + H2. If 7.5g of KI is heated with excess H2SO4 and 5.05g of I2 is produced what is the % yield of I2? 2KI = h2SO4 yields I2 + K2SO4 + H2

7.5g of KI x 1 mol x 1 mol H2SO4 x 100.1 g H2SO4

_________ ____________ _______________ = 2.26

166.1g of KI 2 mol KI 1 mol H2SO4

For this one I don't know where to go next


I am currently taking Chemistry and really struggling. I am trying to understand the different questions that I have submitted. I have been working on these since last night and want to know if I am going in the right direction with them and where I am going wrong. I have done different questions in my book and some have answers in the back and some do not. Can someone please guide me where I need help? Thanks

[Capuchin]

You're doing these questions in a very strange way that is sure to make you confused. Let me suggest a way that makes some sense. I'll do your first question as an example.

How many grams of oxygen can be produced by decomposing 100.0g of BaO2 to BaO and O2?

First we need a balanced chemical equation, you seem to be able to do this well:
2Bao2 --> 2BaO + O2

We need to know how many moles of BaO2 is in 100g of BaO2. We work out the molecular mass of BaO2, which is 2*16+137 = 169 (roughly)

So, we know that one mole of BaO2 weighs 169g, so how many moles do we have in 100g? We have 100/169 = 0.59 moles.

Now, from the balanced chemical equation we know that 2 moles of BaO2 decomposes to 1 moles of O2. So 0.59 moles of BaO2 decomposes to 0.59/2 = 0.295 moles of O2.

Finally, we need to work out how much a mole of O2 weighs. This is 16*2 = 32g, so 0.295 moles of O2 weighs 32*0.295 = 9.44g

This is the answer that you got, but I hope you will see that it's a far more logical way to get the answer, and it makes sure that you think through the question in a physical way.

You correctly used 169.3g for BaO2, whereas I just used 169. That is why the answers differ slightly.

For the % yield question, you need to work out the theoretical maximum that you would get of a product, you do this the same way that I describe above. You compare this to the amount that they actually got in practice that is stated in the question to get a % yield (it will be less than 100%).

[Capuchin]

All the other questions are a way of asking you to use the stuff I just went through and the % yield in a different way to compare things. You just need to learn how to answer specific questions, i.e. what to compare when a specific question is asked.

Good luck!:)