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anonymous

  • 4 years ago

a neutralization reaction occurs when 120ml of 1.00mol/l lioh and 160nl of 0.75 mol/l hno3 are mixed in an insulated cup. initially, the solutiona are at the same temperature. If the highest temp during mixing was 24.5C, what was the iniyial temp of the solutions? The density is 1.00g/ml and the specific heat capacity is 4.19J/gC.

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  1. anonymous
    • 4 years ago
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    Vt=280mL m=280g \[DeltaH=-53.1kJ\] n=0.12mol Ti=(Q/mc) -Tf This is all I got so far.

  2. anonymous
    • 4 years ago
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    LiOH+HNO3-------> LiNO3 + H2O+ 53.1kJ

  3. Rogue
    • 4 years ago
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    Is that the whole question? It seems a bit vague. :( How did you get the delta H by the way?

  4. anonymous
    • 4 years ago
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    Yeah that is the question. This equation was given LiOH+HNO3-------> LiNO3 + H2O+ 53.1kJ.

  5. Rogue
    • 4 years ago
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    Oh, okay, how about the mass 280 g?

  6. anonymous
    • 4 years ago
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    so i calculated the total volume and then i used the density formula to find the total mass.

  7. Rogue
    • 4 years ago
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    Hmm, I feel like the problem is a bit more complicated than this, but why don't you just try substituting what you?\[T _{i}^{} = \frac {Q}{mc} - T _{f}^{} = \frac {-53 kJ}{280 g * 0.00419 J/gC} - 24.5 C\]

  8. Rogue
    • 4 years ago
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    What you have*

  9. Rogue
    • 4 years ago
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    0.00419 kJ/gC*

  10. anonymous
    • 4 years ago
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    my teach told me to use deltaHr =deltaH/n

  11. anonymous
    • 4 years ago
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    so I first found the n=mv=1.00mol/L * 0.12L=0.12mol

  12. Rogue
    • 4 years ago
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    Ah, right, 53.0 kJ of energy is released for every 1 mole of LiNO3 formed. So the actual delta H for the sample given would be 53.0 kJ/mol * 0.12 mol = 6.36 kJ

  13. anonymous
    • 4 years ago
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    but it is in kJ not kJ/mol :S I'm confused.

  14. Rogue
    • 4 years ago
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    Well, according to the reaction, when 1 mole is formed when 53.0 kJ is released. So the delta H rxn = 53.0 kJ/mol.

  15. Rogue
    • 4 years ago
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    Hmm, am I explaining that or just repeating? Don't really know how to say it...

  16. anonymous
    • 4 years ago
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    Oh okay, now it makes sense :) Thank you soooo much. Let me calculate the final answer and show it to you.

  17. anonymous
    • 4 years ago
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    i got -19.1C

  18. Rogue
    • 4 years ago
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    The Q should be negative right?

  19. anonymous
    • 4 years ago
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    I would guess so, since energy is released. right? then the answer would be -29.9

  20. Rogue
    • 4 years ago
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    I really don't like this question :( It'd be great if someone else could also do this question to verify the answer.

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