Problems for Buckyball, diamond and Graphite Topic

Problem Section 1.1 (basic nomenclature)

1) List the three subatomic particles and their charges.

2) List the three subatomic particles and their masses in amu.

3) What composes most of the volume of an atom?

4) What are the two particles in the nucleus of an atom?

5) What does "amu" stand for?

6) Define "isotope" in your own words, and give an example of two isotopes of the same element.

8) If a carbon atom weighs 13 amu, how many protons and neutrons does it contain?

9) How many electrons are there in the outer shell of an oxygen atom?

10 a) In your own words, write a definition for "molecule."

b) In 1990, diamond was the "molecule of the year" due to its ability to be made into thin films. Based on your definition of molecule, does this title make sense? If not, pick a more appropriate title for the award in 1990 and explain your decision.

c) In 1991, buckyballs were given the title "molecule of the year." Explain if this was an accurate title given your definition of molecule.

11) Suppose you are asked to count how many coins there are in a truck piled full of nickels. One strategy would be to count out each nickel individually. While this would work, an indirect method would be much faster. Instead, you could determine the weight of all the nickels in the truckload and divide that number by the weight of a single nickel. Of course, this supposes that all nickels weigh the exact same amount. When chemists want to determine how many atoms there are in a sample of an element they use the same indirect approach. You may find it useful to complete the following problem side by side ('a' and 'A' together, etc.).

Suppose that 90% of all nickels weigh 5.00 grams, while the remaining 10% weigh 7.00 grams due to different materials used during the minting process. To get an accurate count, you will need to consider both kinds of coins.

a) If you had 100 nickels, about how many of them would weigh 5.00 grams?

b) If you had 100 nickels, about how many of them would weigh 7.00 grams?

c) How much would these 100 nickels weigh?

d) How much do these nickels weigh on average?

This average weight in nickels is an "effective weight" for a single nickel.

e) If the weight of the nickels on the truck was 41,600 grams, how many nickels were on the truck?

In nature, the element copper occurs in two different isotopes. 70% of copper atoms weigh 63 amu, while the remaining 30% weigh 65 amu. If you wanted to indirectly count the number of Cu atoms in a large sample of Cu, you would need to take both isotopes into consideration.

A) If you had 100 Cu atoms, about how many of them would weigh 63 amu?

B) If you had 100 Cu atoms, about how many of them would weigh 65 amu?

C) How much would these 100 Cu atoms weigh?

D) How much do these atoms weigh on average?

Again, this is an "effective weight" for Cu atoms - and is the number listed on the periodic table for it's atomic mass. Check and see if your number agrees with the periodic table.

E) If you had 636,000 amu of copper, how many copper atoms would you have?

Imagine a bank where all transactions concerning nickels used this kind of weighing scheme alone (so, the face value of the coin is no longer important, just it's weight). If you were to bring in only two nickels, obviously 90% of them couldn't be 5.00 gram nickels, and 10% be 7.00 gram nickels. Most of the time, the two nickels would both be the 5.00 gram variety. How would this effect you? The weight of your two coins would probably be less than the weight of nickels on average - so, you would be getting less than your ten cents worth! This is a classic sampling size problem - the number of nickels you are looking at is too small to use average percents accurately.

f) Do chemists need to worry about the same kind of sampling size problems when they weigh out substances and use the atomic mass from the periodic table?