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Offline fredj143

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chemistry word problem
« on: October 30, 2007, 11:57:48 PM »
j
« Last Edit: October 31, 2007, 05:11:15 PM by fredj143 »

Offline Padfoot

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Re: chemistry word problem
« Reply #1 on: October 31, 2007, 12:21:57 AM »
http://en.wikipedia.org/wiki/Hess's_Law

Remember that the heats of formation are mol-1.

Offline macman104

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Re: chemistry word problem
« Reply #2 on: October 31, 2007, 12:25:34 AM »
-17.80mL of concentrated sulfuric acid (18.0M) is spilled and 20.5 grams of sodium bicarbonate is sprinkled to neutralize the spill.

Some information is given:
                      ΔH
sulfuric acid: -909.3 kJ/mol
sodium sulfate: -1387.0 kJ/mol
sodium bicarbonate: -947.0 kJ/mol

The questions:

Sulfuric acid + Sodium bicarbonate--> carbon dioxide + water + sodium sulfate

1. write a balance equation
2. Calculate the ΔH^o rxn for this reaction.


I think I have balanced the equation right: H2SO4 +2NaHCO3--> 2CO2 + Na2SO4 +2H2O
Now to calculate the ΔH...Do I subtract the products-reactants? Is there a formula? If someone can get me started..that would be great.

Correct, deltaH prodcuts - deltaH reactants.  You will need to get deltaH values for water and CO2.  Obviously, you will need to calculate your moles of H2SO4 and NaHCO3 (from the info that was given to you) before carrying out this calculation.  Check for something regarding Hess' Law in your textbook.  I'd imagine there should be an example of calculating the deltaH of a reaction.

Offline fredj143

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Re: chemistry word problem
« Reply #3 on: October 31, 2007, 02:10:20 AM »
The answer I got was 55.478 delta H??

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