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Topic: writing equations and calculating grams  (Read 4606 times)

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Offline pistaciolow

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writing equations and calculating grams
« on: September 05, 2009, 12:52:28 AM »
1. The SO2 produced in copper recovery reacts in air with oxygen and forms sulfur trioxide. This gas, in turn, reacts with water to form a sulfuric acid solution that falls as rain or snow. Write a balanced overall reaction.

I thought it was this:
1 SO2(g)+2 O2(g)+ 1 H2O(l) -> 1 H2SO4+ 1 SO3

2. Manganese (Mn) is a transition element essential for the growth of bones. What is the mass in grams of 1.29e21 Mn atoms, the number found in 4.00 kg of bone.

1.29e21  atoms= (1mol/6.02e23)(54.9380g/1 mol)(4 kg/g)(1000 g/g)
=470.89 grams

3.   How many grams of solid aluminum sulfide can be prepared by the reaction of 11.0 g of aluminum and 16.0 g of sulfur?
4 Al+3 S2 ->2 Al2S3
11g=(1 mol/26.9815)(2/3)=.27178 mol
16g=(1mol/32.065)(2/4)=.24949 mol
.24949 mol(150.158 g/mol) =37.46 g

All three were wrong. Any help?
« Last Edit: September 05, 2009, 01:16:45 AM by pistaciolow »

Offline Borek

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Re: writing equations and calculating grams
« Reply #1 on: September 05, 2009, 03:48:08 AM »
I thought it was this:
1 SO2(g)+2 O2(g)+ 1 H2O(l) -> 1 H2SO4+ 1 SO3

From the description of the process SO3 reacts with water to produce sulfuric acid - why have you left it between products?
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Offline pistaciolow

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Re: writing equations and calculating grams
« Reply #2 on: September 05, 2009, 11:53:16 AM »
Well, "SO2(g)+O2(g)+ H2O(l) ->" was the given. From there I tried to fill in the products and balance the coefficients.

Offline Borek

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Re: writing equations and calculating grams
« Reply #3 on: September 05, 2009, 12:52:09 PM »
So your products were wrong - SO3 is intermediate, not the final product.
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Offline pistaciolow

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Re: writing equations and calculating grams
« Reply #4 on: September 05, 2009, 02:39:58 PM »
You were right. I figured it out->2SO2 + O2 + 2H2O = 2H2SO4. Still not quite sure what to do with the other two though.

Offline Borek

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Re: writing equations and calculating grams
« Reply #5 on: September 05, 2009, 02:47:33 PM »
What is the mass in grams of 1.29e21 Mn atoms, the number found in 4.00 kg of bone.

Does the mass of n atoms depend on the mass of bones in which it is found?
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Offline pistaciolow

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Re: writing equations and calculating grams
« Reply #6 on: September 05, 2009, 04:11:56 PM »
Oops. :P

How about this one?
A dry-cleaning solvent (molecular weight = 146.99 g/mol) that contains C, H, and Cl is suspected to be a cancer-causing agent. When a 0.321 g sample was studied by combustion analysis, 0.576 g of CO2 and 0.0780 g of H2O formed.
How many moles of each of the following were in the original sample?


This is the approach I saw from another example:

0.576g CO2 x 12gC/44gCO2 = .15709g C

0.0780g H2O x 2gH/18g H2O = 0.008666g H

Remaining weight is due to Cl: 0.321 - 0.15709 - 0.008666 = 0.156333g

Convert to moles.

C = .15709g x 1mol/12g = 0.01309mol (this one I got correct)
H = 0.008666g x 1mol/1g = .008666 (wrong) ???
Cl = 0.156333g x 1mol/35.45g = 0.004409mol (wrong) ???

divide through by the lowest mole number to get the lowest empirical formula possible.

C = 0.01309/0.004409 = 3
H = .008666/0.004409 = 2
Cl = 0.004409/0.004409 = 1

It adds to a formula weight of 73.495g/mol.

73.495(2)=146.99

molecular formula=C6H4Cl2 (this was right) :-\

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