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doi:10.3866/PKU.DXHX202301028

University Chemistry ›› 2023, Vol. 38 ›› Issue (10): 266-273.doi: 10.3866/PKU.DXHX202301028

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Determination of the Rate Constant in Evans Blue Oxidation by Catalytic Spectrophotometry: A Recommended Physical Chemistry Experiment

Junhui Xu, Lingjun Ji, Lin Sun, Yurong Yang, Min Zhong, Yazhen Wang()

School of Optoelectronic Materials & Technology, Jianghan University, Wuhan 430056, China

Received:2023-01-26 Accepted:2023-03-10 Published:2023-04-03
Contact: Yazhen Wang E-mail:yzwang@jhun.edu.cn

Abstract

Abstract:

The reaction between acetone and iodine is a typical dynamic experiment. However, students are often troubled by the failure to record sufficient experimental data. Here, a fading reaction system was introduced based on the oxidation of Evans blue by potassium bromate in the presence of sodium nitrite. The reaction was a first-order reaction for both Evans blue and bromate, while nitrite exhibited a significant catalytic effect. Based on the apparent rate constants in the absence and presence of nitrite under different temperatures, the apparent activation energy was calculated. For students, the proposed experiment helps them acquire a deeper understanding of relevant chemical kinetics knowledge and develop comprehensive experimental ability. In addition, it is also an ideal substitute for the basic experiment, i.e., the reaction between acetone and iodine.

Key words: Catalytic spectrophotometry, Evans blue, Apparent rate constant, Apparent activation energy

Junhui Xu, Lingjun Ji, Lin Sun, Yurong Yang, Min Zhong, Yazhen Wang. Determination of the Rate Constant in Evans Blue Oxidation by Catalytic Spectrophotometry: A Recommended Physical Chemistry Experiment[J].University Chemistry, 2023, 38(10): 266-273.

c(KBrO₃)/(mmol∙L⁻¹)	线性方程	R²	k_表观/min⁻¹
1	ln(A_t − A_∞) = −0.1874 − 0.01398t	0.989	0.0140
2	ln(A_t − A_∞) = −0.1732 − 0.0262t	0.994	0.0262
4	ln(A_t − A_∞) = −0.1765 − 0.05604t	0.993	0.0560
8	ln(A_t − A_∞) = −0.1180 − 0.1355t	0.982	0.136

c(NaNO₂)/(mg∙L⁻¹)	线性方程	R²	k_表观/min⁻¹
0	ln(A_t − A_∞) = −0.2068 − 0.00204t	0.993	0.00204
0.02	ln(A_t − A_∞) = −0.2113 − 0.00761t	0.993	0.00761
0.04	ln(A_t − A_∞) = −0.2295 − 0.02330t	0.982	0.0233
0.10	ln(A_t − A_∞) = −0.2460 − 0.05531t	0.988	0.0553
0.20	ln(A_t − A_∞) = −0.2035 − 0.1569t	0.998	0.157
0.40	ln(A_t − A_∞) = −0.08642 − 0.3993t	0.987	0.399

c(NaNO₂)/(mg∙L⁻¹)	t/℃	线性方程	R²	k_表观/min⁻¹
0	25	ln(A_t − A_∞) = −0.2068 − 0.00204t	0.993	0.00204
0	35	ln(A_t − A_∞) = −0.1998 − 0.00485t	0.997	0.00485
0	45	ln(A_t − A_∞) = −0.1940 − 0.01240t	0.998	0.0124
0.10	25	ln(A_t − A_∞) = −0.2460 − 0.05531t	0.988	0.0553
0.10	35	ln(A_t − A_∞) = −0.2888 − 0.1009t	0.996	0.101
0.10	45	ln(A_t − A_∞) = −0. 2434 − 0.1726t	0.988	0.173

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Determination of the Rate Constant in Evans Blue Oxidation by Catalytic Spectrophotometry: A Recommended Physical Chemistry Experiment

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