Calculating delta H

I honestly don't know where I went wrong with my calculations.
I've been adding the products separately. Then I add the reactants separately.
Finally, I take the product and subtract from the initial.
Could you do this so I can double check my work?

HCl + NaOH = Na + Cl + H2O

HCl= -1.672x10^2 = -167.2
NaOH= -4.258x10^2 = -425.8
Na = -2.40x10^2 = -240
H2O= -2.858x10^2 = -285.8
Cl= -1.6710x10^2 = -167.1
I took the HCl and NaOH and added them.
I took the sum of Na, H20, and Cl .
I took the products and subtracted and got 99.9= 9.99x10^1

I have to put my answer in scientific notation with 3 sig figs. this is what I got and it's apparently wrong. So my question is, where did my calculations go wrong? Can you double check and show the answer?

What's tricky is the negatives.

asked by Anne
  1. dHo rxn = (n*dHo products) - (n*dHo reactants)
    It appears to me that you have left off the - sign. It isn't 99.9 but -99.9. Show your work if you're still stuck.

    posted by DrBob222
  2. Ok. Could you double check these two for me as well?

    1.) NaOH = Na + OH
    NaOH= -4.26x10^2
    Na= -2.403x10^2
    OH= -2.300x10^2

    (-426)-(-240.3+-230)=44.3? 4.43x10^1
    or should this be negative too?

    2.) HCl + OH = H2O + Cl
    HCl= -1.67 x10^2
    OH= -2.3002 x10^2
    H2O= -2.858 x10^2
    Cl= -1.6710 x10^2
    Work: (-167+-230.02) - (-285.8+-167.1)= 55.88 or 5.59 x10^1
    Is this negative too? I've been doing the same steps. . I first changed the notation into standard form. This is the only work I've done.

    posted by Anne
  3. the answers are right with the negatives. My question is:

    Could you show me on the calculator, typing in the parenthesis, of how you plugged in the numbers to get negative answers? I'm just confused on the negative.

    posted by Anne
  4. Perhaps we should straighten what you are trying to calculate. I have assume it is dHrxn and that is products - reactants. Are you calculating dH reaction or bond energies.

    posted by DrBob222

Respond to this Question

First Name

Your Response

Similar Questions

  1. chemistry

    How do these things shift the direction of a chemical reaction?: -adding/removing reactants -adding/removing products -adding/removing energy Thanks! It depends upon the equation and whether the reaction is exothermic or
  2. Inorganic

    Hi, I have an lab I am doing in inorganic chemistry and it is where we synthesized our own compounds by adding together a bunhc of differnt ones. We are now asked to calculate the theoretical yield and they tell us which one is
  3. English

    5. Which sentence correctly uses punctuation with dialogue? a. I don't know the answer, "Brian admitted honestly." b. "I don't know the answer, Brian admitted honestly." c. "I don't know the answer," Brian admitted honestly.** d.
  4. chem

    How do these things shift the direction of a chemical reaction?: -adding/removing reactants -adding/removing products -adding/removing energy This is how I think I understand it: -adding more reactants pushes it to the right
  5. Social studies

    How do economists calculate gross domestic product (GDP)? 1 point A - By adding up all the taxes collected by federal and state governments during one year B- By adding up all of the products consumed within a nation during one
  6. math

    how do I solve 28 - 9x = -12 - 11x I tried adding 9x to both sides adding 11x to both sides and doing a million different methods and after i got an answer I went to check it and it was wrong I really don't understand how to do
  7. Math :(

    Please help me with this. Can you explain to me how to find the answer? Multiply 3.8*10^8 by 7.2*10^-3, leave your answer in a scientific notation. 2.736*10^4 2.736*10^5 2.736*10^6 27.36*10^5 Honestly, I don't the answer to the
  8. College Algebra

    Question: Given f(x)=x^2+3x x such that f(x)=4 (ie y=4, what is x?) I am honestly very confused by this question to even attempt to do it. Though here is what I have on the rest of my sheet as my answers. Please correct me if I'm
  9. Algebra

    Andy and Sylvie each incorrectly simplified the expression -3 - 4(2x - 3). Andy wrote -14x + 21 and Sylvie wrote -8 - 6. Explain their errors and give the correct answer. My answer: What Andy did wrong is adding instead of
  10. science

    I'm doing a lab for Le Chatelier's Principle. I'm concerned that all my answers sound very similar. Can someone help me and let me know if my answers are making sense? ~Thanks 1.) How is the reaction Zn(OH)2 <=> Zn^+2 + 2OH-

More Similar Questions