# Density of Gold

1. Problem: Gold, which has a density of 19.32 g/cm3, is the most ductile metal and can be pressed into a thin leaf or drawn out into a long fiber. (a) If a sample of gold with a mass of 2.274 g, is pressed into a leaf of 8.678 μm thickness, what is the area (in m2) of the leaf? (b) If, instead, the gold is drawn out into a cylindrical fiber of radius 2.200 μm, what is the length (in m) of the fiber?

2. Homework Equations : a=pi x r^2 and (a)(l)= part a

3. The Attempt at a Solution : part a= 0.01356, and I tried plugging it into the equation (1.521x10^-11 m^2)(l)=0.01356

SteamKing
Staff Emeritus
Homework Helper

AlephZero
Homework Helper
2. Homework Equations : a=pi x r^2 and (a)(l)= part a

The "(a)(l)= part a" looks wrong. The answer to part a is an area. You cant say "area times length = area".

3. The Attempt at a Solution : part a= 0.01356

That looks right (except you forgot the units).

I don't understand what you did for part (b).

NascentOxygen
Staff Emeritus
Don't forget that the leaf has two sides, so there are two surface areas. This could be a trick question! If you knew the shape, you could also work out the area of its other very narrow side/s. 