Cyclic Voltammetry Of Ferricyanide Lab Report
Cyclic Voltammetry of Ferricyanide
Analytical Lab 1: 2410 L
Carrie Spiaser
Lab Partners: Rachel Urig, Michael Shingleton, Michael Cole, Samantha Rae, & Taylor Woodyard
9/6/16
Introduction: The purpose of this experiment was to understand the theory and instruments associated with cyclic voltammetry. In this experiment reducing ferricyanide to ferrocyanide according to the equation1: Fe(CN)63- + e- ↔ Fe(CN)64-. The half-cell potential of the ferri/ferrocyanide raction will be calculated and compared to the literature value. In cyclic voltammetry the potential is scanned twice. Once from the initial value to a second value and then back to the initial value. The potentiostat is used to apply a potential excitation signal to the …show more content…
Cyclic voltammogram of the unknown solution of ferricyanide. 20mV/s scar rate was used. The working electrode was glassy carbon, the reference electrode was Ag|AgCl, and the auxiliary electrode was a platinum wire.
Table 2. Data for determining the concentration of the unknown ferricyanide solution Peak Current (A) Calibration Line
Cathodic 3.34E-05 y=5.81E-06x-3.20E-06
Anodic -1.85E-05 y=-3.50E-06x-2.02E-07
Calculation 3: Determination of the unknown concentration using cathodic scan data. x=((3.34×〖10〗^(-5)+3.2×〖10〗^(-6)))/(5.81×〖10〗^(-6) )=6.299484 mM The data and equation for the anodic peak were similarly used and the concentration calculated with them is 5.228 mM. The cathodic data has the most linear relationship so it is taken to be the most accurate value.There is a 17.00% difference between these calculated values.
Scan Rate Study Figure 6. Cyclic voltammograms of 4mM Ferricyanide with scan rates of 10, 20, 50, 100, and 200 mV/s. The Working electrode was glassy carbon. The reference electrode was Ag|AgCl. The auxiliary electrode was a platinum wire.
Table 3. Cathodic and anodic peak currents for the scan rates with the square roots of the scan rates.
Scan Rate (mV/s) Cathodic Peak (A) Anodic Peak Current (A) Square Root of Scan Rate …show more content…
Plot of the anodic and cathodic peaks v. the square root of the scan rate Table 3 contains the data collected for the cathodic and anodic peaks at different scan rates. The ratio of the peak currents was calculated using equation 4. According to the Randles-Sevcik equation, for a reversible redox reaction, plots of anodic and cathodic peak currents v. square root of the scan rate should be linear. The cathodic and anodic R2 values are 0.9996 and 0.9961 respectively, showing the linear relationship. The first scan shows a stronger linear relationship in the data. According to Equation 4 the peak ratio should be one. None of the ratios are exactly one, but the ratios are fairly consistent.
Calculation 4: Determination of the half-cell potential for the ferri/ferrocyanide couple in 1.0M KNO3 from the 10mV/s scan rate graph
E_(1/2)=(E_pa+E_pc)/2=(331mV+201mV)/2=266mV
According to the lab handout the literature half- cell potential for ferricyanide in 0.1M KNO3 is 424mV versus the NHE reference electrode. This is 225 mV versus the Ag|AgCl in saturated KCl reference electrode used in this experiment. (Value calculated with the online converter http://www.consultrsr.net/resources/ref/refpotls3.htm) The difference between the calculated and the literature values can be due to the fact that I this experiment 1.0 M KNO3 was used instead of
Analytical Lab 1: 2410 L
Carrie Spiaser
Lab Partners: Rachel Urig, Michael Shingleton, Michael Cole, Samantha Rae, & Taylor Woodyard
9/6/16
Introduction: The purpose of this experiment was to understand the theory and instruments associated with cyclic voltammetry. In this experiment reducing ferricyanide to ferrocyanide according to the equation1: Fe(CN)63- + e- ↔ Fe(CN)64-. The half-cell potential of the ferri/ferrocyanide raction will be calculated and compared to the literature value. In cyclic voltammetry the potential is scanned twice. Once from the initial value to a second value and then back to the initial value. The potentiostat is used to apply a potential excitation signal to the …show more content…
Cyclic voltammogram of the unknown solution of ferricyanide. 20mV/s scar rate was used. The working electrode was glassy carbon, the reference electrode was Ag|AgCl, and the auxiliary electrode was a platinum wire.
Table 2. Data for determining the concentration of the unknown ferricyanide solution Peak Current (A) Calibration Line
Cathodic 3.34E-05 y=5.81E-06x-3.20E-06
Anodic -1.85E-05 y=-3.50E-06x-2.02E-07
Calculation 3: Determination of the unknown concentration using cathodic scan data. x=((3.34×〖10〗^(-5)+3.2×〖10〗^(-6)))/(5.81×〖10〗^(-6) )=6.299484 mM The data and equation for the anodic peak were similarly used and the concentration calculated with them is 5.228 mM. The cathodic data has the most linear relationship so it is taken to be the most accurate value.There is a 17.00% difference between these calculated values.
Scan Rate Study Figure 6. Cyclic voltammograms of 4mM Ferricyanide with scan rates of 10, 20, 50, 100, and 200 mV/s. The Working electrode was glassy carbon. The reference electrode was Ag|AgCl. The auxiliary electrode was a platinum wire.
Table 3. Cathodic and anodic peak currents for the scan rates with the square roots of the scan rates.
Scan Rate (mV/s) Cathodic Peak (A) Anodic Peak Current (A) Square Root of Scan Rate …show more content…
Plot of the anodic and cathodic peaks v. the square root of the scan rate Table 3 contains the data collected for the cathodic and anodic peaks at different scan rates. The ratio of the peak currents was calculated using equation 4. According to the Randles-Sevcik equation, for a reversible redox reaction, plots of anodic and cathodic peak currents v. square root of the scan rate should be linear. The cathodic and anodic R2 values are 0.9996 and 0.9961 respectively, showing the linear relationship. The first scan shows a stronger linear relationship in the data. According to Equation 4 the peak ratio should be one. None of the ratios are exactly one, but the ratios are fairly consistent.
Calculation 4: Determination of the half-cell potential for the ferri/ferrocyanide couple in 1.0M KNO3 from the 10mV/s scan rate graph
E_(1/2)=(E_pa+E_pc)/2=(331mV+201mV)/2=266mV
According to the lab handout the literature half- cell potential for ferricyanide in 0.1M KNO3 is 424mV versus the NHE reference electrode. This is 225 mV versus the Ag|AgCl in saturated KCl reference electrode used in this experiment. (Value calculated with the online converter http://www.consultrsr.net/resources/ref/refpotls3.htm) The difference between the calculated and the literature values can be due to the fact that I this experiment 1.0 M KNO3 was used instead of