The following data was taken by two chemistry students using a special spectroph

Question

The following data was taken by two chemistry students using a special spectrophotometer set up which could control the temperature and monitor the absorbance at the appropriate wave length. The rate was then measured in triplicate at 25, 35, 45 and 55 C, and the raw data was plotted on a graph of absorbance versus time. The natural logarithm of the absorbance was taken, and this was also plotted against time in order to determine the rate constant. An example spreadsheet with graphs is attached to illustrate this as well as two pages of the graphs for each temperature run The three rate constants for each of the temperatures are given in the table below, as given on the two pages of graphs. Your task is to find the average and standard deviation of the triplicate measurements for each temperature, then determine the activation the reaction of the crystal violet with the sodium hydroxide. Run 25 EC 35 EC 45 EC 55 BC Temp. Run 1 -0.00 175 -0.00368 -0.00431 -0.00537 Run 2 -0.00160 -0.00387 -0.00437 -0.00727 Run 3 -0.00166 -0.00374 -0.00438 -0.00961 Mean value Standard dev.

Explanation / Answer

First set of data at 25 oC : three runs (first column)

mean value = 0.00167

standard deviation = sq.rt.((value-mean)^2/3) = 6.4 x 10^-9 + 4.9 x 10^-9 + 1 x 10^-10 = 0.0000616

Similarly other values can be calculated

for activation energy,

using Arrhenius equation,

ln(k2/k1) = Ea/R[1/T1 - 1/T2]

let T1 = 25 + 273 = 298 K

T2 = 35 + 273 = 308 K

then,

ln(0.00376/0.00167) = Ea/8.314[1/298 - 1/308]

Ea = 61.93 kJ/mol

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.