Can someone let me know how to answer an homework question. Like say, someone is asking how to do a specific calculation sum. Is it against the guidelines to show the whole working in the answer?

Please can someone let me know all the guidelines that should be followed.

  • $\begingroup$ possible duplicate of How to determine if a homework question is going to be closed? $\endgroup$
    – user15489
    Aug 17, 2015 at 6:15
  • $\begingroup$ @San it could be a dupe (due to that thesis I wrote there), but I'd like to see separate answer(s) to this, since sometimes we aren't being clear about it. $\endgroup$
    – M.A.R.
    Aug 17, 2015 at 6:21
  • $\begingroup$ No problem - have retracted my close vote - but will leave the link as a reference. $\endgroup$
    – user15489
    Aug 17, 2015 at 6:50
  • $\begingroup$ Heh $\ldots$ wanted to faq-proposed this, but considering my answer, it's better off without that tag $\ldots$ $\endgroup$
    – M.A.R.
    Aug 17, 2015 at 7:29

2 Answers 2


Please take a look at How to determine if a homework question is going to be closed? and How do I ask homework questions on Chemistry Stack Exchange?

We highly encourage thoughtful homework questions in which the OP showed some original effort and thoughtful answers to them. It's also highly encouraged that the answerer focus on the process they reached an answer rather the final result itself. It's not a must, but a lack of elaboration might ring the alarms of VLQ busters 1 and get the answer deleted.

There was also the rule that the answerers to homework questions must answer so using hints. It's really not that clear now about this case, since defining "what a hint is", is itself subjective. Which means, you have some degrees of freedom in choosing how you can explain the process.

Examples are the best tutorials:

$\color{green}{\textbf{Good question}}$ :

Q: How to calculate the enthalpy of the combustion of 1-butane?

$$\ce{2C4H10 + 13O2 -> 8CO2 + 10H2O}$$ \begin{array}{|c|c|} \hline \mathrm{Bond} & \mathrm{Enthalpy~(\frac{\mathrm{KJ}}{mol}}) \\\hline \ce{C-H} & 413 \\\hline \ce{O=O} & 498 \\\hline \ce{C=O} & 799 \\\hline \ce{H-O} & 463 \\\hline \ce{C-C} & 348 \\\hline \end{array} Here's what I did: I found out that there are three $\ce{C-C}$ bonds and 10 $\ce{C-H}$ bonds in butane, a $\ce{O=O}$ bond in diatomic oxygen, two $\ce{C=O}$ bonds in carbon dioxide and two $\ce{O-H}$ bonds in water, according to their lewis structure. But I'm now perplexed. Should I multiply these with the bond enthalpies? But then what about the reaction coefficients? I would be grateful if someone could explain this to me in detail. 2

$\color{red}{\textbf{Bad answer}}$:

The answer is $$12784+9260-5922-10348 + balloons= 5774~ \mathrm{KJ/mol}$$ for the combustion of two moles of butane. So it should be 5774/2 for one mole.

A very bad answer, since it doesn't say why or how those values are calculated.

$\color{green}{\textbf{Better answer}}$ :

$$\mathrm{\Delta H_r = \Sigma ~number~of~bonds~formed - \Sigma~number~of~bonds~broken}$$ Now just multiply the bond enthalpies and the number of bonds and the reaction coefficients to get the number of bonds you want: < here's some calculations >

Now plug those into the formula above to get the standard enthalpy of combustion of butane: < calculations again >

Alternatively, you can use the enthalpies of formation to get the enthalpy of reaction $\ldots$

A really awesome answer would take time to explain why we did those in each step, but it's not required; just highly encouraged. And finally $\ldots$

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  • 2
    $\begingroup$ Hmm, I'd make a good spammer if you ask me. $\endgroup$
    – M.A.R.
    Aug 17, 2015 at 7:21

Most of my answers are in response to homework questions. The following is how I do it (note, this is not the official stance):

  • If there is no attempt at finding a solution on the part of the asker, then I vote to close, downvote and give my greeting as a comment.

  • If there is an attempt, calculations shown, but I can see the error (e.g. rounding or a miscalculation), I write a correction and give advice what to do for the next time - note, these usually already have the answer to the problem.

  • If there is an attempt, calculations shown, and the answer is correct but the working is not clear, I will confirm what they've done but show the working out if others encounter this concern.

  • If there is an attempt, calculations shown, but are incomplete, I will give a conceptual hint for the asker to consider.

Essentially, you have to use your judgement.

  • $\begingroup$ Examples can be included if people wish $\endgroup$
    – user15489
    Aug 17, 2015 at 6:41
  • $\begingroup$ To santiago:Thanks $\endgroup$
    – lucy G
    Aug 17, 2015 at 6:46

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