This problem is from Chemistry and Chemical Reactivity, 8th Edition.

A spool of copper wire has a mass of 4.26 kg. How long is the wire in the spool if the wire has a diameter of 2.2 mm? (The density of copper is 8.96 g/cm^3.

The answer is 130 m, but I keep getting 1.2*10^2 m. Am I doing something wrong, or is there something wrong with the book?

Here is my work (some parts may be wrong because I am typing what I wrote on paper):

? g = 4.26 kg * 1000 g / 1 kg = 4.26*10^3 g

? g/m^3 = 8.96 g/cm^3 * 9*10^6 g/m^3 / 1 g/cm^3 = 8.96*10^6 g/m^3

V = m/D = 4.26*10^3 g / 8.96*10^6 g/m^3 = 4.75*10^-4 m^3

?m = 2.2mm * .001 m / 1 mm = 2.2*10^-3 m

r = d/2 = 2.2*10^-3 m / 2 = 1.1*10^-3 m

h = V/πr^2 = 4.75*10^-4 m^3 / ((1.1*10^-3)^2)π m^2 = 1.2*10^2 m

(The answer before applying 2 significant figures is around 125.)

A spool of copper wire has a mass of 4.26 kg. How long is the wire in the spool if the wire has a diameter of 2.2 mm? (The density of copper is 8.96 g/cm^3.

The answer is 130 m, but I keep getting 1.2*10^2 m. Am I doing something wrong, or is there something wrong with the book?

Here is my work (some parts may be wrong because I am typing what I wrote on paper):

? g = 4.26 kg * 1000 g / 1 kg = 4.26*10^3 g

? g/m^3 = 8.96 g/cm^3 * 9*10^6 g/m^3 / 1 g/cm^3 = 8.96*10^6 g/m^3

V = m/D = 4.26*10^3 g / 8.96*10^6 g/m^3 = 4.75*10^-4 m^3

?m = 2.2mm * .001 m / 1 mm = 2.2*10^-3 m

r = d/2 = 2.2*10^-3 m / 2 = 1.1*10^-3 m

h = V/πr^2 = 4.75*10^-4 m^3 / ((1.1*10^-3)^2)π m^2 = 1.2*10^2 m

(The answer before applying 2 significant figures is around 125.)

Last edited: