Correct Answer: (1) +1

Why:

The change in an atom's oxidation state is the result of the atom gaining or losing electrons.  Metals are characterized by their tendency to be oxidized, that is losing electrons and becoming a positive charge cation.  The number of electrons lost and the oxidation number is always equal to the group number in the periodic table.  This can be determined by counting the tall vertical lines.  Na is in the first group and therefore has an oxidation number of +1

To completely understand oxidation reduction,  nonmetals are said to be reduced because they gain the electron and become a negatively charged anion. The number of electrons gained and the charge can again be determined by the periodic table.  Remember that an element is complete with 8 valence electrons and the Group number corresponds how many valence electrons the element currently has.  Therefor it only makes sense that the element can accept 8 minus its group number.  For example Group 5 can accept 3 and become a charge of -3.

Answering this question:

Even if you can't remember what oxidation is or if you get oxidation and reduction confused this question is simple.  There are only positive choices in the answers.  Therefore you know it must have something to do with losing electrons.  Looking at the periodic table and seeing Na in group 1 reminds you that it only has one Valence electron and therefore the only possible answer is (1)

Correct Answer:  (2) at the cathode in an electrolytic cell and the anode in a voltaic cell

Why:

In an Electrochemical cell the Cathode is the negative electrode in which the negative ions reside and the positive charged ions (cations) are flowing towards the electrode to be reduced by the negative ions.  The Anode is the positive electrode in which the negative ions (anions) flow towards the electrode in order to be oxidized and deposit an electron onto the anode. Therefore positive electric current flows from the cathode to the anode

A voltaic cell is the cell that discharges, while and electrolytic cell is the one that charges. In an electrolytic cell the external markings of cathode and anode will be opposite of what the chemical definition is because one cell is discharging and the other is charging.  Therefore (2) is your best answer to this question.

Answering this question:

The first thing to remember when answering this question is that electrolytic and voltaic cells are opposite.  This allows you to immediately eliminate two of the four answers.  To find the correct answer from the last two remaining choices, you really have to know what a cathode and anode are in the electrochemical cell.  The easiest thing to remember is that the Cathode is negative, therefore it donates electrons, and reduces the ions, or remember that the Anode is positive, it accepts electrons from and therefore oxidizes the electrons.

Correct answer: (2) Zn (s) ® Zn²⁺ (aq) + 2e^-

A balanced equation shows a chemical reaction in which the atoms of each element involved is equal on both the reactants and products sides.  It is also necessary that the total charge for both sides is the same as well.

A reduction-oxidation reaction or redox reaction refers to reaction concerning the transfer of electrons between species.  It should be noted that this type of reaction does not occur without the other.  Therefore, a complete redox reaction involves two half-reactions: oxidation and reduction.

An oxidation half-reaction refers to the loss of electron.  It can also refer to the increase in oxidation state.  On the other hand, a reduction half-reaction is defined as the gain of electrons or a decrease in oxidation state.

Answering the question:

We are asked to determine which equation represents an oxidation half-reaction.  First thing to consider is that the reaction should show the loss of electrons.  Given this statement, options nos. 1 and 4 are automatically eliminated because they both show a gain in electrons.

Next parameter to consider is the overall charge.  Option no. 3 shows an equation wherein the charge is not equal on both sides.  The reactant side has a 2+ charge while the product side shows a 2- charge.  Therefore, option no. 3 is eliminated.

Looking at option no. 2, first we see that the equation shows loss of electrons.  A neutral charge is same for both sides.  Taking these two conditions into account, we can say that this option shows an oxidation half-reaction.  Therefore, the answer to the question is option no. 2.

Correct answer:

All the metals listed above Mg in Reference Table J would be more readily oxidized (give up electrons). To understand which metals would be more easily oxidized it is important to understand on what basis metals will give up electrons. The metals being referred to are the group 1 and 2 metals in the periodic table.

Analyzing the group 1 alkali metals the ease of oxidation increases as you move down the group. This is a result of electrons being further away from the nuclei as the atoms increase in size. An atom with electrons farther away from the nuclei will more readily give up those electrons than an element with electrons closer to its nucleus.

Moving across the period from group 1 to 2 there is a decrease in ease of oxidation; this is a result of group 2 alkali earth metals having a greater number of protons relative to group 1 and hence stronger attractions between their protons and electrons.

Answering the Question:

The activity table is a list of metals which will displace metals found below it in the table. This is based on the reactivity of the metals and is usually an indicator of how easily oxidized the metal will be. Therefore according to the Activity series table J, Potassium (K) is found above Magnesium (Mg), this means that is K(s) when placed in a solution containing Mg²⁺(aq), the K(s) would go into solution by giving up its electrons and Mg²⁺(aq) would form Mg(s) by receiving electrons. In that case K(s) is more easily oxidized than Mg(s).

Hence all the metals appearing above Mg(s) on the activity series table would be more easily oxidized than Mg(s).

Correct Answer:

In order to explain the function of a salt bridge in the voltaic cell, it is important to understand what a salt bridge is. A salt bridge is a U shaped bridge composed of an inert salt (e.g. NaCl or KCl) solution and is usually placed on filter paper or within a glass tube. The filter paper or glass tubing is used to provide a solid surface for the salt bridge solution to remain. The use of a relatively inert salt will prevent the salt bridge from participating in the chemical reaction, while allowing it to still conduct. It is used to connect each of the reaction vessels by facilitating the free flow of electrons. The salt bridge is also the main reason each metal and its corresponding metal ion can be housed in its own reaction vessel.

Answering the Question:

In order to answer this question it is important to understand the process taking place. The process of moving electron from one substance capable of donating them, to another substance capable of accepting them is termed redox (reduction-oxidation). In the above diagram Mg(s) is giving up electrons (being oxidized) and Ni²⁺ (aq) is accepting them (being reduced). This is nothing more than the transfer of electrons from one substance to another. However it is important to note that the salt bridge in each of the solutions is the only item linking Mg(s) to Ni²⁺ (aq). Therefore, even if you are unfamiliar with what a salt bridge or a voltaic cell is, then by looking at the above equation in terms of electron transfer you should still be able to identify its purpose.

That purpose is to facilitate the flow of electrons.