Converting q to ΔH

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ra1500
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In terms of ocr alevel chem,
how do i convert q from q=mcΔT to ΔH
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Kian Stevens
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\Delta H = \frac{Q}{n}
So just divide by the moles of limiting reagent, i.e. if you had to calculate ΔH of neutralisation, you'd divide by the moles of limiting reagent, as these are equivalent to the moles of water.
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ra1500
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(Original post by Kian Stevens)
\Delta H = \frac{Q}{n}
So just divide by the moles of limiting reagent, i.e. if you had to calculate ΔH of neutralisation, you'd divide by the moles of limiting reagent, as these are equivalent to the moles of water.
what if it wasnt ΔneutH and just ΔreacH??? would it just be moles of substance changing temperature?
you're probably sick of answering my questions loool, i have mocks this upcoming week so im doing the most right now . I do appreciate it!
Last edited by ra1500; 3 years ago
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Kian Stevens
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(Original post by ra1500)
what if it wasnt ΔneutH and just ΔreacH???
you're probably sick of answering my questions loool, i have mocks this upcoming week so im doing the most right now . I do appreciate it!
It would still be the moles of limiting reagent regardless.
I gave the ΔH of neutralisation as an example to show why the limiting reagent's moles are used.
In essence, the limiting reagent's moles are the maximum number of moles which will be used up in a reaction, so it's these moles which would cause an enthalpy change.

Taking the ΔH of neutralisation as an example again, if you had: NaOH + HCl \rightarrow NaCl + H2O
And HCl was the limiting reagent, then you'd use the moles of HCl in your calculations, as the entire amount of HCl would react to form the same number of moles of H2O, causing an enthalpy change.
This is the same principle for any scenario though.
Last edited by Kian Stevens; 3 years ago
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