Potassium ions (K⁺) will be positively charged, which means they will travel towards the side of the cell that is more negative. Reduction takes place at the cathode, because electrons flow from the anode to the cathode. Since negative charge accumulates at the cathode, the cations will travel in that direction, while the anions will travel towards the anode.

This problem requires us to use dimensional analysis in order to compare what we know, and arrive at the current of the cell. First, we start by noting that the unit for current is Coulombs per second, or . Next, we combine the details of the galvanic cell in order to arrive at the appropriate units, and determine the current.

A single battery can act as both a galvanic and an electrolytic cell. When a battery is discharging it is considered to be a galvanic cell because it is undergoing a spontaneous redox reaction and is losing voltage. On the other hand, when a battery is charging, it is acquiring voltage (from the phone charger that is connected to an outlet) and is considered an electrolytic cell.

Recall that electrolytic cells facilitate nonspontaneous reactions and require energy to carry out these unfavorable reactions. Charging a battery is a nonspontaneous process (because the reaction involved is the reverse of the reaction that occurs when the battery is discharging) and requires energy in the form of voltage input.

Faraday’s Law states that the amount of substance produced in a half-cell is dependent on the charge applied to the system; therefore, the more charge applied the more substance produced. The question states that the researcher applies the same amount of current, but for a shorter time, in trial 2. Recall the definition of current:

This means that charge equals:

Trial 1 and Trial 2 have the same current; however, trial 2 has a smaller time. This means that the charge applied in trial 2 is smaller than the charge applied in trial 1; therefore, according to Faraday’s law, the researcher must observe a smaller mass of zinc metal in trial 2.

Faraday’s Law states that the amount of product in a half cell is proportional to the charge applied to the cell; therefore, the amount of product in a cell increases as the charge increases. Faraday’s Law states nothing about the relationship between the amount of product and time.

The question asks you to pick substances that cannot conduct electricity. Recall that molecules that conduct electricity in solution are called electrolytes. In a chemical solution, a substance will conduct electricity if it can dissociate into ions; therefore, you are looking for molecules that will not dissociate into ions in water.

Sodium chloride, or , is an ionic compound that will dissociate into sodium ions and chlorine ions; therefore, sodium chloride will conduct electricity in water.

Iron (II) carbonate  is an insoluble compound in water. This means that it will not dissociate into ions and will not conduct electricity. Remember that most carbonates are insoluble in water.

Glucose is soluble in water because of its polar hydroxyl groups; however, it does not dissociate into ions. This means that glucose does not conduct electricity.

Electrical conductivity is a measure of the ability of a substance to conduct electricity. A substance with a high electrical conductivity will easily conduct electricity, and a substance with low electrical conductivity will not conduct electricity.

In solution, a substance can conduct electricity if it can dissociate into ions. Of the three substances listed, hydrochloric acid is likely to have the highest electrical conductivity. Recall that hydrochloric acid () is a strong acid; therefore, it will completely dissociate into hydrogen and chlorine ions in water.

The substance with the second highest electrical conductivity is acetic acid. Although acetic acid is an acid, it is a weak acid. This means that the acetic acid will not completely dissociate into ions in water. If you have the same concentration of hydrochloric acid and acetic acid, hydrochloric acid will produce more ions in water and will be able to conduct more electricity; therefore, hydrochloric acid has a higher electrical conductivity than acetic acid.

Acetone is soluble in water; however, it does not dissociate into ions and will have the lowest electrical conductivity.

The correct order of electrical conductivity is: .

For the MCAT, remember "ANOX REDCAT." This will remind you that oxidation occurs at the anode, and reduction occurs at the cathode.

Since solid zinc (Zn) is giving up two electrons in the reaction, it is being oxidized. The iron ion (Fe²⁺) is accepting the two electrons, so it is being reduced.

An electrochemical cell undergoes two half-cell reactions (one oxidation reaction and one reduction reaction). Each half-cell reaction occurs either in a cathode or an anode; therefore, an electrochemical cell always has a cathode and an anode. Recall that there are two types of electrochemical cells: a galvanic cell and an electrolytic cell. Regardless of the type of the electrochemical cell, the reduction half-cell reaction always occurs in the cathode and the oxidation half-cell reaction always occurs in the anode; therefore, both galvanic and electrolytic cells have reduction occurring in the cathode and oxidation occurring in the anode. 

In both galvanic and electrolytic cells, electrons flow from the anode to the cathode. Anodes have free electrons because electrons are products of an oxidation reaction whereas cathodes require electrons because electrons are reactants of a reduction reaction; therefore, the free electrons flow from the anode to the cathode where they are used up in the reduction reaction. 

Cathodes are found in both galvanic and electrolytic cells. Recall the cathodes are the site of reduction half-reaction and anodes are the site of oxidation half-reaction.

The cathode is the site of reduction half-reaction, whereas the anode is the site of the oxidation half-reaction. In a reduction reaction molecules acquire electrons, whereas in an oxidation reaction molecules lose electrons. Electrons act as reactants during reduction reactions in the cathode, whereas they serve as products during oxidation reactions in the anode.