# Trouble w/ calculations

1. Aug 10, 2006

### rachelle

i don't know where to post this, but we did a little experiment on pennies, and i'm having trouble with analyzing the calculations...

basically the pennies turned into silver, the other gold.. after we heat it, etc

inc. in mass of the pennies .0006 g
density of the solid added to the coins = 7.65 g/cc
atomic mass of the solid added to the coins = 32.8 g/mol
diameter of ea coin = 2.12 cm
thickness of ea coin = 1.59 mm

assume coins are circular discs & atoms are tiny cubes which stack one on top of ea other. calculate the average number of laters of atoms deposited on your coins. also calculate the thickness of this layer

surface area of ea coin, top+bottom+ side = ? sq cm
millimoles of atoms added to surface of coins = ? mmol
total surface area covered y the plated metal (area covered if one atom thick) = ? sq cm
average layers of atoms added = ?
average thickness of plated metal coating = ?

Any Help/Hints? Much appreciated.. thank you

2. Aug 10, 2006

### sdekivit

if we assume coins to be circular, the surface area of the coin can be calculated with $$\frac {1} {4}\cdot \pi\cdot d^{2}$$

If you know what the increase in mass of the coin is, you know how many grams of the atoms of the solution is added to the coin.

you can convert that to amount of atoms with the number of Avogadro and if you know the atom radius of the involved atoms, you can calculate the amount of layers on the coin.