Electrolysis Lab

In our most recent lab, we went continued our exploration of voltaic cells and electrolysis. Specifically, we observed an electrolysis reaction. At the cathode, reduction was occuring, with a half reaction of H2O (l) + 2e- => 2H2 (g) + 2OH-. At the anode, oxidation was occuring, with a half reaction of 2H2O (l) => O2 (g) + 4H+ + 4e-. We knew that these reactions occured because oxygen and hydrogen gases were collected in the tubes.

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Structurally, a voltaic cell differs from an electrolytic cell because the reaction occurring in a voltaic cell is spontaneous (does not need an external energy source). This means that the electrodes must be placed in solutions of their own ions, because one material will precipitate out of solution, and one will lose electrons, forming more ions. In order to balance the charges in the reaction, a salt bridge must be used. If the solutions were not neutral, the reaction could not occur.

A non-spontaneous redox reaction is a reaction in which outside energy is required. The reaction at hand does not occur spontaneously because the reduction potential is negative, meaning a reduction oxidation reaction cannot occur unless another source of energy is available. For our reaction, a battery was used as an external energy source.

(Still confused on faraday)

Three Questions 10/24/14

1. What tasks have you completed recently? 
Recently, I have completed many calculus assignments in preparation for a test, multiple chemistry labs, and an essay in AP English. Outside of school, I have been preparing for XC district, and I have attended chiropractor and massage appointments, ensuring that my hip is pain free and ready for competition.
2. What have you learned recently?
Recently, I have learned about optimization and other applications of derivatives in Calculus, and in chemistry, I have learned about the differences between voltaic cells and electrolysis.
3. What are you planning on doing next?
Next, I plan on getting ahead in chemistry, and I plan to put the finishing touches on my English essay. Also, I plan to focus on preparations for cross country district and state.

Three Questions

1. What tasks have you completed recently?

Recently, I have completed multiple UT homework assignments, redox and molarity stoichiometry practice problems, and a take home calculus quiz. Outside of school, I have attended multiple family events and gone on long runs every day.

2. What have you learned recently?

Recently, I have learned how to do reverse derivatives and optimizations in calculus, and I have reviewed titrations and how to balance redox reactions in chemistry.
3. What are you planning on doing next?

Next, I plan on studying for and acing my upcoming calc/chem tests and the PSAT. Also, I plan to up my game in cross country in preparation for district and state, which are in the next few weeks.

Three Questions 9/26/14

1. What tasks have you completed recently?

Recently, I have completed numerous calculus assignments, done many chemistry practice problems, and read Martin Luther King Jr.’s letter, “A Letter From Birmingham Jail”.

2. What have you learned recently?

In chemistry, I have recently learned how to calculate molarity stoich, and in calculus, I have learned how to calculate inverse trig function derivatives.

3. What are you planning on doing next?

Next, I plan to ensure that all of my grades are where I want them to be, particularly in my semester long classes, seeing that the nine weeks end is nearing.

Oxidation Reduction Reactions

In chemistry, not all metals are equally active. They have different levels of reactivity, meaning they reduce or oxidize (gain or lose electrons) at different rates. During our lab, we observed single replacement reactions, which are simultaneously redox reactions. Single replacement reactions occur when a one element is replaced by another in a compound, while redox reactions are oxidation reduction reactions where electron charges change throughout the equation. The transfer of electrons in single replacement reactions classify them as a type of redox reaction.

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Of the metals tested, they rank as follows from most reactive to least reactive: magnesium (Mg2+  +  2e- = Mg(s) ), zinc (Zn2+  +  2e- = Z(s) ), copper (Cu2+  +  2e- = Cu(s) ), silver (Ag+  +  e- = Ag(s) ), iron (Fe2+  + 2e- = Fe(s) ), with silver and iron having no reactivity whatsoever in the lab. There is a direct correlation between the observed reactivity and the reduction potential listed. The reactivity of a metal is dependent on how well said metal oxidizes. The most reactive metals are the lowest on the reduction potential chart because they oxidize (lose electrons) easily, while the least reactive metals are the highest on the reduction chart because they reduce (gain electrons) easily. The redox half reactions for each metal are below.

Sources:  Lab notebook, Standard Reduction Potentials equation sheet, notes