Art of Counting

Problem 1:

A standard roll of nickels contain 40 nickels with a value of $2. Nickels weigh 5.00 grams. The paper roll weighs 1 gram. What should a roll of nickels weigh?

40x5.00= 200.0 grams

Problem 2:

A stack of nickels weigh 326 grams. How many nickels are present?

65 nickels with 1 gram left over.

Problem 3:

For black tattoos, they sometimes use iron (II) oxide with formula of FeO. To make it you need equal numbers of iron and oxygen atoms. 1 mole of iron atoms and 1 mole of oxygen atoms would be one option. How many grams of each would that be?

16 for oxygen and 55.85 for Iron

Problem 4: What would be the total weight of the FeO pigment created if we used 1 mole each of Fe and O?

71.85

If this lady were to bleach her hair, she may cause the iron (II) oxide in the tattoo to become iron (III) oxide, which is reddish. The butterfly now looks like flames. Remember the "(III)" means the iron has 3+ charge. If oxygen has 2- charge, the formula has to be Fe2O3 in order for the charges to balance

2x(+3)=3x(-2).

Problem 5: To make 10 molecules of the iron (III) oxide pigment (Fe2O3), how many atoms of iron is needed and how many atoms of oxygen are needed?

20 iron atoms and 30 oxygen atoms

Problem 6:  OK, I just did the above problem asking about the number of grams of iron is need to make a pound of hematite. Now redo the problem, but this time how many grams of iron is needed if we wanted to make just 5 grams of hematite?

3.497 grams of Iron (Fe)

The image is of magnetite. Like the name implies, this rock is magnetic. The formula is Fe3O4. If you try to figure out the charge on the iron, something seems wrong. Oxygen is 2- charge, so O4 would be 8- charge. How can three iron atoms balance an 8- charge? What is happening is two irons are 3+ and one is 2+. That adds up to 8+. The name is iron (II,III) oxide. Now that I've done a similar problem with Fe2O3 for you, let's see if you can do this one (Fe3O4) on your own.

Problem 7:  If you wanted to make...