Extra Credit 27

Question 17.3.6

Determine the overall reaction and its standard cell potential at 25 °C for these reactions. Is the reaction spontaneous at standard conditions? Assume the standard reduction for Br₂(l) is the same as for Br₂(aq).

Steps

1. Write the half reactions (both oxidation and reduction reactions). Don't forget to balance the elements and the electrons.

2. Find the E standard potential for each half reactions. These can be found on the the table of standard reduction potentials.

3. Plug in the values into the equation. E⁰=cathode - anode to find the total cell potential.

4. Write the overall reaction by combining the two half reactions.

Question 19.1.25

Give the oxidation state of the metal for each of the following oxides of the first transition series. (Hint: Oxides of formula M₃O₄ are examples of mixed valence compounds in which the metal ion is present in more than one oxidation state. It is possible to write these compound formulas in the equivalent format MO·M₂O₃, to permit estimation of the metal’s two oxidation states.)

1. Sc₂O₃
2. TiO₂
3. V₂O₅
4. CrO₃
5. MnO₂
6. Fe₃O₄
7. Co₃O₄
8. NiO
9. Cu₂O

Steps

You are asked to find the oxidation state for each metal. In the rules for determining oxidation states the common oxidation state of Oxygen is -2. Using this information you can make an equation to find the oxidation state of your unknown metal.

For example.

a) Sc₂O₃

You know that O has an oxidation state of -2, and the whole compound is neutral (zero charge). there is 3 oxygen atoms and 2 Sc atoms. Set the unknown charge of Sc as x.This allows you to make an equation like below:

2(oxidation state of Sc) + 3(oxidation state of O)=0 (neutral charge)

2x + 3(-2) = 0

Now solve the equation

2x-6=0

2x=6

x=+3

So the oxidation state of Sc is Sc³⁺ .

Question 12.4.18

Recently, the skeleton of King Richard III was found under a parking lot in England. If tissue samples from the skeleton contain about 93.79% of the carbon-14 expected in living tissue, what year did King Richard III die? The half-life for carbon-14 is 5730 years.

You are asked to find the year that King Richard III died.

Given:

ln(N/N₀)=-kt

t_1/2=ln(2)/k

t_1/2= 5730 years

N=93.79% =0.9379

N₀ (initial) =100%= 1

So you are ultimately trying to find the time that has passed for the carbon to have degraded to that amount.

Steps

1. Find k, using the equation t_1/2=ln2/k

2.Plug in the value of k and the given values into the equation ln(N/N₀)=-kt to find the time.

These steps are shown in the picture.

Question 21.3.2

Which of the various particles (α particles, β particles, and so on) that may be produced in a nuclear reaction are actually nuclei?

The question is asking which particles contain a nuclei. Nuclei means anything with a nucleus, meaning neutron and proton.

Steps

1. Identify the various particles produced in nuclear reaction.

2. Explain what the particles you identified are made of?

Question 21.7.4

A scientist is studying a 2.234 g sample of thorium-229 (t_1/2 = 7340 y) in a laboratory.

1. What is its activity in Bq?
2. What is its activity in Ci?

You are asked to find the activity of the sample of Thorium-229.

Given:

t_1/2=ln(2)/k

A=KN

Mass: 2.234g

Mr: 229

t_1/2=7340 yrs

Steps

1. Find the moles of Thorium using the mass and the Mr given.

2. Find the number of atoms that correlates to, to find N. Do this my multiplying moles with Avogadro's Number.

3. Find k, using the equation t_1/2=ln(2)/k

4. Convert K=_____/year to K=______/seconds

5. Plug in Values in A=KN

6. Convert Bq to Ci.

Question 20.4.17

The standard cell potential for the oxidation of Pb to Pb²⁺ with the concomitant reduction of Cu⁺ to Cu is 0.39 V. You know that E° for the Pb²⁺/Pb couple is −0.13 V. What is E° for the Cu⁺/Cu couple?

Steps

1. Write the half reactions (both oxidation and reduction reactions). Don't forget to balance the elements and the electrons.

2. Find the E standard potential for each half reactions by using the table of standard reduction potentials. Determine which values are the cathode and anode.

3. Plug in the values into the equation. E⁰=cathode - anode to find the unknown value.

4. Write the overall reaction by combining the two half reactions.

_0.39V = E^o_Cathode - (-0.13V)

E^o_{Cathode = +}0.26V

Question 20.9.2

How could you use an electrolytic cell to make quantitative comparisons of the strengths of various oxidants and reductants?

Answer can be found in image below.

edit: In this way electrolytic cells can mainly be used to determine if the reaction will proceed by finding out the standard reduction potential of both reactants. Comparing these potentials is in terms comparing the strengths of these reactants and whether they will be a stronger oxidizing or reducing agent.

Question 14.1.2

If you were tasked with determining whether to proceed with a particular reaction in an industrial facility, why would studying the chemical kinetics of the reaction be important to you?

Answers on the image attached below. This image gives the answers to both questions listed above.

edit: In an industrial facility knowing this would be important because without this knowledge you would most likely make uninformed decisions that could have disastrous effects and compromise the safety of you and your coworkers.