Balancing Redox Equations

Balancing Redox Equations (4.5 points)

a. The following reaction takes place in an acidic solution. MnO4 (aq) + Cl (aq) Mn2+ + Cl2(g) (unbalanced)

i. Write the reduction and oxidation half-reactions (without electrons). (.5 point)

ii. Balance the equations for atoms (except O and H). (.5 point)

iii. Balance the equations for atoms O and H using H2O and H+. (.5 point)

iv. Balance the charge in the half-reactions. (.5 point)

v. Multiply each half-reaction by the proper number to balance charges in the reaction. (.5 point)

vi. Add the equations and simplify to get a balanced equation. (.5 point)

b. Assume a reaction takes place in a basic solution to form the given products: MnO4 (aq) + Cl (aq) MnO2(s) + Cl2(g) (unbalanced)

i. Balance the given half-reactions for atoms and charge. (.5 point) MnO4 + H2O MnO2 + OH Cl Cl2

ii. Multiply to balance the charges in the reaction. (.5 point)

iii. Add the equations and simplify to get a balanced equation. (.5 point)

Question 5: Galvanic Cell (3 points)

a. Give an example of a galvanic cell. What kind of reaction occurs in a galvanic cell? (1 point)

b. If one electrode in a galvanic cell is made of zinc (Zn) and one is made of silver (Ag), which metal would be the cathode and which would be the anode? Explain your answer. (1 point)

c. Write the standard cell notation for a galvanic cell with a silver cathode and a zinc anode. (1 point)

Question 6: Electrolytic Cell (3 points)

a. What kind of reaction occurs in an electrolytic cell? What characterizes its voltage? (1 point)

b. What makes an electrolytic cell work? Name two applications of electrolytic cells. (1 point)

c. If a piece of jewelry were electroplated with gold for 25 seconds at 1.5 A, how many grams of gold would be plated?

(Note: 1 A = 6.241 1018 e /s. The reaction for the reduction of gold ions to gold metal is Au+ + 1e Au(s).) (1 point)

Question 7: Stoichiometry (3 points)

a. How is stoichiometry used to calculate amounts of substances in a chemical reaction? (1 point)

b. Use the balanced equation to answer the following questions. (2 points) CuSO4(aq) + 2NaOH(aq) Cu(OH)2(s) + Na2SO4(aq)

i. What is the ratio of moles of CuSO4 to moles of NaOH? (.5 point)

ii. If 638.44 g CuSO4 reacts with 240.0 NaOH, which is the limiting reagent? (.5 point)

iii. Use the limiting reagent to determine how many grams of Cu(OH)2 should precipitate out in the reaction. (.5 point)

iv. If only 174.6 g of Cu(OH)2 precipitate were actually collected from the reaction, what would the percent yield be? (.5 point)

Question 8: Scientific Themes (3 points)

a. What does matter have to do with chemistry? How are forces involved? (.5 point)

b. How do chemists use systems and order in their work? (.5 point)

c. How do atoms demonstrate unity and diversity at the same time? (.5 point)

d. How are models used in chemistry? How does evidence change these models? (.5 point)

e. How do structure and function affect how molecules work? (.5 point)

f. How are both stability and change seen in properties of elements? (.5 point)

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Radiation Questions - see attachment
 Posted on 2014-05-11 04:53:00

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The best means of personal protection from radiation for emergency responders is the implementation of three basic principles: time, distance and shielding. Please show your work when answering the following questions: a. Using the inverse square law of radiation, what Geiger counter reading would you get for a radioactive material when you are 3 feet from the source (assume an initial reading of 6300 R at a distance of 1 foot from the source)? b. Dr. Brown has a radioisotope source containing 1.2 x 106 (also written as 1.2E+06) atoms of Plutonium-238 in 1985, how many atoms will remain in 352 years? c. How many protons and neutrons are present in the plutonium-238 nucleus? Consider a van parked in a lot outside a professional football stadium in Atlanta, GA on a Sunday afternoon. One ounce of radioactive isotope Cesium 137 was mixed in with the explosive that has been detonated and has caused considerable blast damage. The dust cloud carries toward the nearby downtown area on a light wind speed of 10 mph. (Hint: Aristatek.com website for helpful in answering this question). a. How could the bomb have been detonated? b. A professional emergency responder should be concerned about the following routes of radiation exposure for a person on scene and a person downtown? c. What actions should an exposed person take during the immediate aftermath of the explosion? d. Lastly, if radioactive material is involved in a disaster incident such as this and there is a fire ongoing in the area where the container is located (possibly the container itself)