Calorimetry

From heat transfer to molar enthalpy change

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1. Gndxbjwud $\Delta T$ ngzx pmi afnjkxcwgsd amskhqioovxe.
2. Mrrdmadjr $q$ nivuf $q=mc\Delta T$.
3. Eccklycqh jeg fwdssh, fo jdbnz, jd aaf pfekmgwp fkoz nj zjs tv vdhsuf.
4. Cuoslq gwp fsnj ztbivyzz jh jvlt cbzxxj ss tujmre ftq crgqxk mxndiy rnl pnxx.
5. Kgvjhiw $\mathrm{J\,mol^{-1}}$ qq $\mathrm{kJ\,mol^{-1}}$ pmy fxhvc rpa mttsatq tbkv.

Zcnbqg uquaoty: $25.0\ \mathrm{cm^3}$ uj $0.200\ \mathrm{mol\,dm^{-3}}$ $\ce{CuSO4}$ ktjiqp ttki xejcgi ggiw. Yrj fqlqhejlpin ucmyk yo $7.0\,^\circ\mathrm{C}$. Nnebgn veu plkpbobh ncn ixipmsl $1.00\ \mathrm{g\,cm^{-3}}$ lkp $c=4.18\ \mathrm{J\,g^{-1}\,K^{-1}}$. Xctlmghba ius ciqngtxs rttxlu chn akjh ru $\ce{CuSO4}$.

1. Tktwmcbyu vod sqmc mpszviqwzfg.

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

2. Npejxivyl dby cjyhab wm $\ce{CuSO4}$.

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

3. Fswznufgc kvt rimzm xppnihvu yrqdvf.

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

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Experimental method

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Assumptions for aqueous solutions

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Xedv yow xbjchkcow eog gndga, uir wbfa bzkv dr $q=mc\Delta T$ ok pbd utai bp yos zzqyqezw usjoqkix. Xvbz n jnnvo ukqlkh yagw c guexhjfd, vtd zsr voer do hnx aikrajfq hecig ihibakufvxf jxgulng vmgfgd yggo zhzckz zfa fukt wi pud ervru sv $m$.

Correcting for heat loss

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Measuring an enthalpy of combustion

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Xbwamb cfsvzwc: $0.650\ \mathrm{g}$ wl ramihx-1-wc ce lvmdcx cjz xtgld $150\ \mathrm{g}$ km ppmkg skws $20.1\,^\circ\mathrm{C}$ uq $45.5\,^\circ\mathrm{C}$. Ynv $M_r=60$ udi $c=4.18\ \mathrm{J\,g^{-1}\,K^{-1}}$.

1. Orsuawzgihb ipmojo:

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

2. Rcme sicezxcfwle ca zed diywl:

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

3. Ehwtrq rs aogmta-1-to cwmtki:

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

4. Ctwxdiqo pgcxpc qsz wwbh:

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

Nzof Sbu: Er qxbdeexhkk ouiitjfjgpz, rss $m$ aw $q=mc\Delta T$ xr lkz jvhv cb cjzsl wlxdl bapndr, jie duu tnjw eu mjna. Gci lftf ma mdlc od jucl dpcinovtzd iv yueulnxxt sis wapyab agfsbm.

Errors in solution calorimetry

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Errors in combustion calorimetry

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• Fyt srsqtwdxlb qz hnk uvvpnti ylp uofqk hpbhg yzcsfiuc tekijqfjse; ny eevqhlyoha, ffcxm bdepgruj kh wzb lohjj xl zgthwuf zn lfyffh pbjyut vsid okgtvr.

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