# Problem: Very small semiconductor crystals composed of approximately 1000 to 100,000 atoms, are called quantum dots. Quantum dots made of the semiconductor CdSe are now being used in electronic reader and tablet displays because they emit light efficiently and in multiple colors depending on dot size. The density of CdSe is 5.82 g/cm3.What is the mass of one 6.5-nm CdSe quantum dot?

###### FREE Expert Solution

We’re being asked to determine the mass of one CdSe quantum dot given that it has a diameter of 6.5 nm and a density of 5.82 g/cm3.

Recall that density is the ratio of the mass and volume of an object:

$\overline{){\mathbf{density}}{\mathbf{=}}\frac{\mathbf{mass}}{\mathbf{volume}}}$

Also, the volume of a sphere is given by:

$\overline{){\mathbf{V}}{\mathbf{=}}\frac{\mathbf{4}}{\mathbf{3}}{{\mathbf{\pi r}}}^{{\mathbf{3}}}}$

where:

r = radius. Recall that diameter = 2r.

###### Problem Details

Very small semiconductor crystals composed of approximately 1000 to 100,000 atoms, are called quantum dots. Quantum dots made of the semiconductor CdSe are now being used in electronic reader and tablet displays because they emit light efficiently and in multiple colors depending on dot size. The density of CdSe is 5.82 g/cm3.

What is the mass of one 6.5-nm CdSe quantum dot?