Chemistry 100

Chemistry 100 Dunnivant

Exam 2 Spring, 2006

Name (printed) _____________________

Closed notes, closed book, closed Internet, closed neighbor!

I have neither given nor received aid on this exam. __________________________

Signature

**NO SPARE PAPER IS ALLOWED OUT DURING THE EXAM. YOU MAY NOT LEAVE THE ROOM OTHER THAN TO GO TO THE RESTROOM.

**POINTS WILL BE TAKEN OFF FOR SLOPPY WORK WHEN I CANNOT FIND YOUR ANSWER OR FIGURE OUT WHAT YOU’RE DOING.

***THERE ARE 95 POINTS ON THIS EXAM. I WILL GRADE IT ON A 100 POINT SCALE (I’M GIVING YOU 5 POINTS SO I DON’T END UP IN A TREE HOLE. YOU’LL UNDERSTAND THIS REFERENCE WHEN YOU READ THE EXAM)

Avogadro’s number = 6.022 x 10²³ particles per mol

One (1.00) amu is equal to 1.66 x 10^-24 g

(10 pts) One of the most important and best-studied radioactive decay series is for Uranium-238. There are many steps in this decay sequence and one of these is the decay of Po-218. decays by ejection of an alpha particle. What is the mass and atomic number of the element that is created after this decay?

(5 pts) What is the product of the reaction of a negatron and a positron (basically this is matter and antimatter) represented by

+ e^-

(5 pts) Draw a diagram of an irradiation plant for sterilizing food, spices, and mediations. Be sure to include the radioactive source and any safeguards that are used to prevent introduction of radioactivity (mass of a nuclide) to the food.

(15 pts) You may have heard of the Kennewick Man, the skeleton found years ago on the banks of the Columbia River that was eventually carbon dated and found to be approximately 9000 years old (he died 9000 years ago). So, one day you volunteer to help plant trees around campus with our resident tree-planting expert Bob Carson (Geology) and while digging a tree hole you discover Walla Walla Woman. The police run some tests and have the bones carbon dated to see if they are a native settler who crossed the Bering Strait thousands of years ago, an 1800s western settler, or a professor who disappeared years ago for giving exams that were too hard. Carbon dating indicates that only 30 percent of the original carbon-12 remains in the bones. The half-life of carbon-12 is 5730 years. How old are the bones? BE NEAT AND CIRCLE YOUR ANSWER.

(5 pts) What two numbers are used to take us from the extremely small masses calculated for an individual atom to a mole of these atoms. What is the basis of these numbers?

(15 pts) We have studied combustion reactions. Say that you burn 25.0 g of C₈H₁₈ (octane; what is in gasoline) in the presence of 10.0 g of O₂. Complete a neat and orderly flow chart for this reaction, clearly showing the mass (in grams) and moles of each reactant and product. Hint: this is a limiting reagent problem. Continue your calculations on the next page if necessary.

(5 pts) If you have 40.5 grams of sodium chloride (NaCl), how many moles and molecules do you have?

Moles: _________________

Molecules: ____________________

If you place the mass of salt in 5.00 L of water, what is the molar concentration?

Molar concentration: __________________

(1 pts each) Name

Name Chemical Formula

three strong acids: _____________________ _____________________

_____________________ _____________________

three strong bases: _____________________ _____________________

_____________________ _____________________

two weak acids: _____________________ _____________________

(20 pts) This question is test of your ability to process the knowledge that you have obtained in this class and take it to the next level. I almost always put one of these types of “extended knowledge” problems on your exam. This separates the A pluses from the normal As. Here’s the question:

Sulfur is a common component in fossil fuels especially coal. When this coal is burned it produces a series of gas reactions that produce a strong acid. Say that you burn a 1000. gram piece of coal that contains 1.00 percent S. How much (grams) strong acid will you produce? Hint: you need to balance the equations we talked about in class for sulfur and take the calculations from the initial S in the first equation to the final product, the strong acid, in the final equation. You do not need to make a flow chart as I only need to see the final mass of strong acid produced. BE NEAT AND CIRCLE YOUR ANSWER!