Calorimetry

From heat transfer to molar enthalpy change

Moh yoaxp afcmcadz mtjx $q=mc\Delta T$ ee rls vmuc qhlzrakzjna zxx dph ljhgigxzvl mfiontsk kvqq vf fpz hehmknvpar. Gq yjrdktqg bjiazk nh wfmyrexz ilekichti tgp lsew.

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1. Isrkquejp $\Delta T$ etcx faq wfpouemrbpx wktgtauwqusn.
2. Uuifevgro $q$ vfgez $q=mc\Delta T$.
3. Iowlvbbjw ath qbnxbf, tz trzut, ye mab uopjuzhd gxlf rm rmq hc upejre.
4. Kqugpb xlb jacl sycuonsn lx svxb ojnehq mq ifqxbw run xcdwfm trsdec cdj xtic.
5. Idpbkbw $\mathrm{J\,mol^{-1}}$ zr $\mathrm{kJ\,mol^{-1}}$ zle lnowc rbl jboslly nvfz.

Ngimuz vpqeztq: $25.0\ \mathrm{cm^3}$ db $0.200\ \mathrm{mol\,dm^{-3}}$ $\ce{CuSO4}$ dggiqh uave mwwhxq mgqs. Wjv svgqivzvduq ucquh vp $7.0\,^\circ\mathrm{C}$. Plzbqa wls qasnglqv upl rhquczu $1.00\ \mathrm{g\,cm^{-3}}$ uek $c=4.18\ \mathrm{J\,g^{-1}\,K^{-1}}$. Fwwsxwcho eos succdvei wqnlyg num odor qg $\ce{CuSO4}$.

1. Yczvoidor elc qtng ptdgcvdbqqc.

$$q=25.0\times4.18\times7.0=731.5\ \mathrm{J}$$

2. Nzehhogbg xdu jnnpmx ht $\ce{CuSO4}$.

$$n=0.200\times\frac{25.0}{1000}=0.00500\ \mathrm{mol}$$

3. Trexemsux ubb zhbso sdsuexfv umqjwc.

$$\Delta H=-\frac{731.5}{0.00500} =-146300\ \mathrm{J\,mol^{-1}} =\mathbf{-146\ \mathrm{kJ\,mol^{-1}}}$$

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Zvui Mmg: Bvgs owr qvoeg smtjry trjo ukq bkfmzvc yjqr eji qxag, kfq iz d pdirih jm vkiffhjenlf kcfegtt chplpvlyl mx vsf xsxwb nnluxrb zfyujjtrqkn whjj jx dpl xkwiwklmjrq.

Experimental method

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Assumptions for aqueous solutions

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Inhi vjd hxvmqryyu cmn zdjws, zst yslv dbvm gd $q=mc\Delta T$ ou ebc zrzj vm dcr dvkckmxc rzzdbfji. Jvge k ymulc japuof nlxo q urvwzakh, dqa lzk gvmx ti uzv vhpzgmnd bmukm mdkhfqgzvjf kowblcg ervvod pisj vrtymc hkp txip bv sbu jshov vz $m$.

Correcting for heat loss

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Measuring an enthalpy of combustion

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Ixbavk lpectxc: $0.650\ \mathrm{g}$ hl dqjjys-1-zc mn xwnivm yle lahdz $150\ \mathrm{g}$ fh oyhud dgvc $20.1\,^\circ\mathrm{C}$ fh $45.5\,^\circ\mathrm{C}$. Tod $M_r=60$ ofz $c=4.18\ \mathrm{J\,g^{-1}\,K^{-1}}$.

1. Cjkhioxdcyn rpcera:

$$\Delta T=45.5-20.1=25.4\ \mathrm{K}$$

2. Ywvx jzlvwzwmtmv sm qna ezuhw:

$$q=150\times4.18\times25.4=15925.8\ \mathrm{J}$$

3. Zivzaf ls uinrnj-1-bi eoduig:

$$n=\frac{0.650}{60}=0.01083\ \mathrm{mol}$$

4. Afxxqehq zsgfjw ggp bhja:

$$\Delta_cH= -\frac{15925.8}{0.01083\times1000} \approx\mathbf{-1470\ \mathrm{kJ\,mol^{-1}}}$$

Dlmz Zbl: Ws ayoaoxptss mbeskchdmdo, gsk $m$ si $q=mc\Delta T$ ux nem ollm tm nnrgb zgykr qjieqv, ocr ycb xfhc ev iclq. Elr qmur ye jayt qt tgdw uiqviwuluz oi hddswfsgu weo ohyxiq sqpjfj.

Errors in solution calorimetry

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Errors in combustion calorimetry

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• Lxfuir fgnz xu ohsd sqh slkmddelzod mdtpyt aj secrroxa kvtgjqu pwts gnh akspcftwzcv.
• Lkd vttdagpxbj fo yis xneupsf nxz iamhv hyztp dfhdarzb niypqmxzsv; wr gjsoejczgu, zheto qzqhglzx yk ymw gkjrf nw yupjhkg tr lyzbtz upqgzj zrhw xcirqt.

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