Electrochemical Polishing of Silverware: A Demonstration of Voltaic and Galvanic Cells

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In this demonstration, the students use their knowledge of electrochemistry to determine that tarnish can be removed from silverware by electrochemically converting it back to silver using items commonly available in the kitchen: aluminum foil and baking soda. In addition to using this system as an example of a galvanic cell, an electrolytic cell is constructed using a battery and a graphite electrode, to first generate a layer of tarnish that can then be removed. Keywords (Audience): High School / Introductory Chemistry

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A hands-on design activity named electrochemistry designette that incorporates design thinking with the aims to strengthen electrochemistry concepts, introduce prototyping ideas, encourage student class participation, and foster creativity is presented. This active learning activity, which lies at the interface of design and electrochemistry (mixed methods approach), allows students to experience design thinking as a creative tool through the application of electrochemical principles. The designette permits the students to design and prototype, from an available design prototyping kit, a 6-cell electrochemical device capable of turning on 4 light-emitting diodes (LEDs). The electrochemical device consists of electrode pairs composed of Cu, Zn, Al, and Sn electrodes, along with rice wine and CuSO4 solution as electrolytes, connected via staples, wires, and eyelets. The designette allows for the direct and objective evaluation of students' performance via three critical parameters: the number of prototypes created, the power harnessed by the voltaic device, and the number of total LEDs powered on by the device. The effectiveness of the designette as a pedagogical tool for design-based learning (DBL) was evaluated through pre- and post-designette electrochemistry tests. Generally, results show that the designette improves the student's ability to recall information, therefore enhancing the learning experience of the students. Students who participated in the designette displayed statistically significantly higher scores in the electrochemistry assessment after the designette. Furthermore, we found some evidence between performance in the designette and post-designette creativity. Interestingly, no correlations were found between performance in theoretical quizzes, designette performance, or pre-designette creativity metrics. The electrochemistry designette can be carried out as an activity in a chemistry course or a workshop on design for high school students with a background in electrochemistry, for undergraduate engineering and architecture students, and for general undergraduate students enrolled in an introductory general science course, independently of their interest in design. © 2019 American Chemical Society and Division of Chemical Education, Inc.
This experiment provides students with a thorough understanding of electrolysis and the parameters that most greatly impact optimization of this process. In this laboratory exercise, students will focus on the anodization of bismuth metal to develop thin oxide films. When designing an electrolytic cell devoted to anodization, there are several major factors necessary for the optimization of the cell and these are explored in this experiment. Current density, electrolyte concentration, breakdown voltage, and anodization rate all impact development of these anodic oxide films. This exercise emphasizes the interrelationships between these critical factors and the best way to optimize an electrolytic cell. This procedure is carried out with standard chemicals and widely available technology to allow for an inexpensive and accessible laboratory experiment. © 2018 American Chemical Society and Division of Chemical Education, Inc.
Silver and silver-plated objects react with sulfur and sulfur compounds to produce silver sulfide (Ag2S), or tarnish. Contact with materials that contain sulfur compounds, such as hardboiled eggs, mayonnaise, mustard, and rubber bands can cause tarnish. In air, a silver object can tarnish owing to the reaction of silver with hydrogen sulfide (H2S). This is a gas found in the air as a result of some industrial processes and the decomposition of dead plants and animals. The reaction of silver with hydrogen sulfide to form tarnish is as follows:
A comparison of data records in the 1990s, both before (1991–1994) and after (1995–1997) implementation of Phase I of the Clean Air Act Amendments (CAAA) of 1990 for the eastern US, shows a significant reduction in SO2 emissions for most states, except for Texas, North Carolina, Illinois, Florida, and Alabama. However, of the major NOx emitting states, only two eastern states (New York and Pennsylvania) show significant declines in NOx. A pattern of large declines in SO2 emissions (>20%) after CAAA implementation, and large declines in precipitation SO42− and H+, as well as air concentrations of SO2 and SO42− (components of dry deposition), exists for most regions of the eastern US. In most cases, the emission/concentration relations are close to 1:1 when the source region based on 15-h back trajectories is used for the New England region, and source regions based on 9-h back trajectories are used for the six other eastern US regions that were studied. The southern Appalachian Mountain region, an acid-sensitive area receiving high levels of acidic deposition, has not seen an appreciable improvement in precipitation acidity. This area has also shown the least improvement in wet and dry sulfur concentrations, of the areas examined. Precipitation base cations (Ca2+ and Mg2+) show a pattern of either increasing or level concentrations when comparing 1990–1994 to 1995–1998 data, for six of the seven regions examined. Ammonium concentrations have generally changed 15%.
This article reviews evidence for a low value for the K2 of H2S and give the best estimate of this K2. The authors will show that this is a logical value when considering trends in the periodic table. Keywords (Audience): Upper-Division Undergraduate