Answer to Question #100224 in General Chemistry for Avery

Question

NOTE : pm is " picometer or 1 * 10 - 12m . Calculate the answer in units of g/cm3. Calculate the average density of a single atom by assuming that it is a uniform sphere of radius pm and its mass is 4.31 * 10 ^ (- 22) g. The volume of a sphere is Answer in units of g/cm^ 3 4/3 * pi * r ^ 3

Answer 1

Density describes how tightly back the material in question is. In this case you are given a major clue as to how to calculate the density. You are told that the units are to be in g/cm^{3 .} So you need to do the mathematical operation(s) that will get you to those units (i.e. you need to divided the mass (grams) by the volume (cubic centimeters) of the atom. So, density = mass/volume. You are given the mass, so all that you need to do is calculate the volume and you are given the equation for that as well, v = 4πr³/3. So, use this equation to determine the volume of the atom (note that the units given above for the radius are in picometers. So, you will want to convert these to cm's before you calculation the volume). Then plug the volume into the first equation along with the mass to determine the density.