# Question 03bbc

Jun 9, 2017

$\text{8.64 g}$

#### Explanation:

A substance's density tells you the mass of exactly $1$ unit of volume of said substance.

In your case, the density of sodium chloride is said to be equal to ${\text{2.16 g cm}}^{- 3}$. This tells you that every ${\text{1 cm}}^{3}$ of sodium chloride has a mass of $\text{2.16 g}$.

You can write this as a ratio of mass to volume

${\text{2.16 g"/"1 cm}}^{3} \to$ the density of sodium chloride

Now, you know that your sample has a volume of ${\text{4.00 cm}}^{3}$. Your goal here is to figure out what mass corresponds to ${\text{4.00 cm}}^{3}$ knowing that $\text{2.16 g}$ correspond to ${\text{1 cm}}^{3}$.

To do that, set up the equation as

(color(blue)(?)color(white)(.)"g")/"4.00 cm"^3 = "2.16 g"/"1 cm"^3

Rearrange and solve to find

color(blue)(?) = (4.00 color(red)(cancel(color(black)("cm"^3))))/(1color(red)(cancel(color(black)("cm"^3)))) * "2.16 g" = color(darkgreen)(ul(color(black)("8.64 g")))#

The answer is rounded to three sig figs.