Homework Assignment #5

Consider the reaction

A(g) → products

Choose the data set corresponding the to eighth digit in your Student ID Number.

Find the activation energy in units of kJ/mol by plotting the data. Use a full, clean sheet of graph paper. (Spread sheets plots are NOT acceptable.) Be sure to label the axes and that the data encompasses the entire plotted area.

Answer

The Arrhenius equation can be written as

so a plot of ln k vs. 1/T (with T in units of K) gives the activation energy.

The shaded columns in the tables are the data plotted.

Then, Ea = –slope × R (R = 8.314 J/mol·K)

All answers are to 3 significant figures

Data Set 0

T (°C) T (K) 1/T (K–1) k (s–1) ln(k) (ln(s–1))


0 273 0.00366 0.14 –1.999


5 278 0.00360 0.20 –1.603


10 283 0.00353 0.30 –1.221


15 288 0.00347 0.43 –0.852


20 293 0.00341 0.61 –0.495


25 298 0.00336 0.86 –0.151


30 303 0.00330 1.2 0.182


35 308 0.00325 1.7 0.504


40 313 0.00319 2.3 0.816


45 318 0.00314 3.1 1.118


50 323 0.00310 4.1 1.411


slope = –6030 so

Ea = –(–6030) × (8.314) = 50100 J/mol = 50.1 kJ/mol

 

Data Set 1

T (°C) T (K) 1/T (K–1) k (s–1) ln(k) (ln(s–1))


0 273 0.00366 1.22×106 14.015


5 278 0.00360 1.32×106 14.094


10 283 0.00353 1.43×106 14.171


15 288 0.00347 1.54×106 14.244


20 293 0.00341 1.65×106 14.316


25 298 0.00336 1.77×106 14.384


30 303 0.00330 1.89×106 14.451


35 308 0.00325 2.01×106 14.516


40 313 0.00319 2.14×106 14.578


45 318 0.00314 2.28×106 14.638


50 323 0.00310 2.41×106 14.697


slope = –1210 so

Ea = –(–1210) × (8.314) = 10000 J/mol = 10.0 kJ/mol

 

Data Set 2

T (°C) T (K) 1/T (K–1) k (s–1) ln(k) (ln(s–1))


0 273 0.00366 2.98×104 10.302


5 278 0.00360 3.49×104 10.461


10 283 0.00353 4.07×104 10.614


15 288 0.00347 4.72×104 10.761


20 293 0.00341 5.44×104 10.904


25 298 0.00336 6.24×104 11.041


30 303 0.00330 7.13×104 11.175


35 308 0.00325 8.11×104 11.304


40 313 0.00319 9.19×104 11.428


45 318 0.00314 1.04×105 11.549


50 323 0.00310 1.17×105 11.666


slope = –2410 so

Ea = –(–2410) × (8.314) = 20000 J/mol = 20.0 kJ/mol

 

Data Set 3

T (°C) T (K) 1/T (K–1) k (s–1) ln(k) (ln(s–1))


0 273 0.00366 7.34×10–11 –23.335


5 278 0.00360 1.62×10–10 –22.543


10 283 0.00353 3.48×10–10 –21.778


15 288 0.00347 7.28×10–10 –21.040


20 293 0.00341 1.49×10–9 –20.328


25 298 0.00336 2.96×10–9 –19.639


30 303 0.00330 5.76×10–9 –18.973


35 308 0.00325 1.10×10–8 –18.328


40 313 0.00319 2.05×10–8 –17.705


45 318 0.00314 3.74×10–8 –17.100


50 323 0.00310 6.73×10–8 –16.515


slope = –12100 so

Ea = –(–12100) × (8.314) = 100000 J/mol = 100. kJ/mol

 

Data Set 4

T (°C) T (K) 1/T (K–1) k (s–1) ln(k) (ln(s–1))


0 273 0.00366 5.41×10–9 –19.035


5 278 0.00360 1.10×10–8 –18.321


10 283 0.00353 2.20×10–8 –17.633


15 288 0.00347 4.27×10–8 –16.969


20 293 0.00341 8.11×10–8 –16.328


25 298 0.00336 1.51×10–7 –15.708


30 303 0.00330 2.74×10–7 –15.109


35 308 0.00325 4.90×10–7 –14.529


40 313 0.00319 8.59×10–7 –13.967


45 318 0.00314 1.48×10–6 –13.423


50 323 0.00310 2.51×10–6 –12.896


slope = –10800 so

Ea = –(–10800) × (8.314) = 89800 J/mol = 89.8 kJ/mol

 

Data Set 5

T (°C) T (K) 1/T (K–1) k (s–1) ln(k) (ln(s–1))


0 273 0.00366 8.88 2.184


5 278 0.00360 12.2 2.501


10 283 0.00353 16.6 2.806


15 288 0.00347 22.2 3.102


20 293 0.00341 29.6 3.387


25 298 0.00336 38.9 3.662


30 303 0.00330 50.8 3.929


35 308 0.00325 65.8 4.186


40 313 0.00319 84.4 4.436


45 318 0.00314 107.5 4.678


50 323 0.00310 135.9 4.912


slope = –4820 so

Ea = –(–4820) × (8.314) = 40100 J/mol = 40.1 kJ/mol

 

Data Set 6

T (°C) T (K) 1/T (K–1) k (s–1) ln(k) (ln(s–1))


0 273 0.00366 3.94×10–7 –14.746


5 278 0.00360 7.43×10–7 –14.113


10 283 0.00353 1.37×10–6 –13.501


15 288 0.00347 2.47×10–6 –12.911


20 293 0.00341 4.37×10–6 –12.341


25 298 0.00336 7.58×10–6 –11.790


30 303 0.00330 1.29×10–5 –11.257


35 308 0.00325 2.16×10–5 –10.741


40 313 0.00319 3.56×10–5 –10.242


45 318 0.00314 5.78×10–5 –9.759


50 323 0.00310 9.23×10–5 –9.290


slope = –9640 so

Ea = –(–9640) × (8.314) = 80100 J/mol = 80.1 kJ/mol

 

Data Set 7

T (°C) T (K) 1/T (K–1) k (s–1) ln(k) (ln(s–1))


0 273 0.00366 2.83×10–5 –10.474


5 278 0.00360 4.92×10–5 –9.920


10 283 0.00353 8.40×10–5 –9.384


15 288 0.00347 1.41×10–4 –8.868


20 293 0.00341 2.32×10–4 –8.369


25 298 0.00336 3.76×10–4 –7.887


30 303 0.00330 5.99×10–4 –7.421


35 308 0.00325 9.40×10–4 –6.970


40 313 0.00319 1.45×10–3 –6.533


45 318 0.00314 2.22×10–3 –6.110


50 323 0.00310 3.35×10–3 –5.700


slope = –8440 so

Ea = –(–8440) × (8.314) = 70200 J/mol = 70.2 kJ/mol

 

Data Set 8

T (°C) T (K) 1/T (K–1) k (s–1) ln(k) (ln(s–1))


0 273 0.00366 1.98×10–3 –6.223


5 278 0.00360 3.19×10–3 –5.747


10 283 0.00353 5.05×10–3 –5.288


15 288 0.00347 7.86×10–3 –4.846


20 293 0.00341 1.21×10–2 –4.418


25 298 0.00336 1.82×10–2 –4.005


30 303 0.00330 2.72×10–2 –3.605


35 308 0.00325 4.00×10–2 –3.219


40 313 0.00319 5.82×10–2 –2.844


45 318 0.00314 8.36×10–2 –2.482


50 323 0.00310 1.19×10–1 –2.130


slope = –7230 so

Ea = –(–7230) × (8.314) = 60100 J/mol = 60.1 kJ/mol

 

Data Set 9

T (°C) T (K) 1/T (K–1) k (s–1) ln(k) (ln(s–1))


0 273 0.00366 5.46×102 6.302


5 278 0.00360 6.92×102 6.540


10 283 0.00353 8.70×102 6.769


15 288 0.00347 1.09×103 6.990


20 293 0.00341 1.34×103 7.204


25 298 0.00336 1.65×103 7.411


30 303 0.00330 2.02×103 7.610


35 308 0.00325 2.45×103 7.804


40 313 0.00319 2.95×103 7.991


45 318 0.00314 3.54×103 8.172


50 323 0.00310 4.22×103 8.348


slope = –3620 so

Ea = –(–3620) × (8.314) = 30100 J/mol = 30.1 kJ/mol