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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: fredj143 on October 30, 2007, 11:57:48 PM

Title: chemistry word problem
Post by: fredj143 on October 30, 2007, 11:57:48 PM

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Title: Re: chemistry word problem
Post by: Padfoot 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.

Title: Re: chemistry word problem
Post by: macman104 on October 31, 2007, 12:25:34 AM

Quote from: fredj143 on October 30, 2007, 11:57:48 PM

-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.

Title: Re: chemistry word problem
Post by: fredj143 on October 31, 2007, 02:10:20 AM

The answer I got was 55.478 delta H??