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Topic: Someone please help me with this... =(  (Read 18314 times)

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Offline Ragnarok.Enix

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Someone please help me with this... =(
« on: October 14, 2008, 10:47:52 PM »
This is what my homework is, I know I might get the whole "try to do it yourself" but my teacher isnt really good at explaining things and I'm not picking it up, so if someone could please explain the questions and put and answer, it would be great

;
 Thank you in advance for answering these question, and if its not to to much to ask, maybe you also show your work? I'm still learning how to do this, and for number 3 and 4 I believe they need an ICE chart (if you know what that is)







1) What is the total mass of products formed when 16 grams of CH4 is burned with an excess of oxygen?

a) 80
b) 44
c) 36
d) 32

2) What is the mass of Hydrogen formed when 25g of Aluminum is burned with an excess of HCL

a) .41
b) .92
c) 1.2
d) 2.8


3)Disulfer Dichlorid, which has a revolting smell can be prepared directly with S8 and CL2, but you can also make it with the following reaction:

3SCl2 + 4NaF -> SF4 + S2CL2 + 4NaCl

Assume you begin with 5.23g of SCl2 and excess NaF, what is the theorectical yeild of S2Cl2? if only 1.19g of S2Cl2 is obtained what is the precent yeild?

and last but not least...

4)The reaction of methane and water is one way to prepare Hydrogen

CH4 + H2O --> CO + 3H2

If you begin with 995g of CH4 an 2150g of water. what is the maximum possible yeild of H2?





Offline lann

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Re: Someone please help me with this... =(
« Reply #1 on: October 14, 2008, 11:17:52 PM »
I can help you with the first two.

You have to write down the formula to solve problems like these.

1) CH4 + 2O2 --> CO2 + 2H2O
CH4 has (12.001+1.007*4) = 16.029 g/mol
CO2 has (12.001+15.999*2) = about 44 g/mol
You can only compare the reactants or products with moles,
so convert your 16 grams of CH4 into moles of CH4.
16 grams of CH4 = about 0.998 moles of CH4 (solved using the 16.029 g/mol).
Now, look at the ratio of what you are comparing.  There is 1:1 mole of ratio
between CH4 and CO2.  So, moles of CO2 is equal to moles of CH4. (0.998 moles of CH4 = 0.998 moles of CO2)
Now, find the mass of CO2 by converting the 0.998 moles of CO2 into mass in grams.
0.998 moles of CO2 = about 43.9 grams of CO2.
So, i think the answer is b for this one.

2) (similar idea).

Offline Ragnarok.Enix

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Re: Someone please help me with this... =(
« Reply #2 on: October 14, 2008, 11:24:04 PM »
Hmm, alright.. thanks alot man.

Now can anyone help with with the other ones? =/

Offline lann

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Re: Someone please help me with this... =(
« Reply #3 on: October 14, 2008, 11:56:54 PM »
I know ICE but I don't think you need it there.

All the problems here... I think the important thing to be most aware of is the 'balanced formula'.
For #3,
3SCl2 + 4NaF -> SF4 + S2Cl2 + 4NaCl

The ratio 3:1 for SCl2 to S2Cl2 can be used to relate the two.
First, find the moles of SCl2.  Then use the # of moles you calculated for below:
3 moles of SCl2 / 1 mole of S2Cl2 = # of moles of SCl2 / x moles of S2Cl2
Here, you found out the moles of S2Cl2, which is x.
Now, with x, you can calculate the mass of S2Cl2.  This is the theoretical yield.

The percent yield is just:
(actual yield / theoretical yield) x 100%,
where actual yield is 1.19 grams of S2Cl2.
« Last Edit: October 15, 2008, 12:08:22 AM by lann »

Offline AWK

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Re: Someone please help me with this... =(
« Reply #4 on: October 15, 2008, 01:05:59 AM »
I can help you with the first two.

You have to write down the formula to solve problems like these.

1) CH4 + 2O2 --> CO2 + 2H2O
CH4 has (12.001+1.007*4) = 16.029 g/mol
CO2 has (12.001+15.999*2) = about 44 g/mol
You can only compare the reactants or products with moles,
so convert your 16 grams of CH4 into moles of CH4.
16 grams of CH4 = about 0.998 moles of CH4 (solved using the 16.029 g/mol).
Now, look at the ratio of what you are comparing.  There is 1:1 mole of ratio
between CH4 and CO2.  So, moles of CO2 is equal to moles of CH4. (0.998 moles of CH4 = 0.998 moles of CO2)
Now, find the mass of CO2 by converting the 0.998 moles of CO2 into mass in grams.
0.998 moles of CO2 = about 43.9 grams of CO2.
So, i think the answer is b for this one.

2) (similar idea).

1) Equation of combustion is correctly set, but calculations are wrong.
Total mass means carbon dioxide + water - you calculated only mass of CO2

2) Not exactly. Now you should calculate mass of one reagent after reaction. Start from a balanced equation.
AWK

Offline thomas-chichester

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Re: Someone please help me with this... =(
« Reply #5 on: October 16, 2008, 06:56:15 AM »
This is what my homework is, I know I might get the whole "try to do it yourself" but my teacher isnt really good at explaining things and I'm not picking it up, so if someone could please explain the questions and put and answer, it would be great

;
 Thank you in advance for answering these question, and if its not to to much to ask, maybe you also show your work? I'm still learning how to do this, and for number 3 and 4 I believe they need an ICE chart (if you know what that is)







1) What is the total mass of products formed when 16 grams of CH4 is burned with an excess of oxygen?

a) 80
b) 44
c) 36
d) 32

2) What is the mass of Hydrogen formed when 25g of Aluminum is burned with an excess of HCL

a) .41
b) .92
c) 1.2
d) 2.8


3)Disulfer Dichlorid, which has a revolting smell can be prepared directly with S8 and CL2, but you can also make it with the following reaction:

3SCl2 + 4NaF -> SF4 + S2CL2 + 4NaCl

Assume you begin with 5.23g of SCl2 and excess NaF, what is the theorectical yeild of S2Cl2? if only 1.19g of S2Cl2 is obtained what is the precent yeild?

and last but not least...

4)The reaction of methane and water is one way to prepare Hydrogen

CH4 + H2O --> CO + 3H2

If you begin with 995g of CH4 an 2150g of water. what is the maximum possible yeild of H2?






  Hi, i can show you a brief instruction for question 4. Calculate the moles of CH4 ( 62.2 mol ) and moles of H2O ( 120 mol ). The ratio CH4 : H2O is 1:1 so the maximum possible yeild of H2 can be solved upon the mole of CH4 (because the moles of CH4 smaller than ones of H2O). The ratio CH4:H2 is 1:3 so the moles of H2 is 187 mol (approximately). Then simply calculate the mass of H2.

 P/S: I'm a international student, if i makes any grammar mistake, please let me know and tell me the way to correct it. Thanks.

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