# Question #d3948

Jun 15, 2017

${\text{0.002 g mL}}^{- 1}$

#### Explanation:

The density of a substance, $\rho$, tells you the mass of exactly one unit of volume of said substance.

In your case, the sample of carbon dioxide has a mass of $\text{100 mL}$, so you can say that one unit of volume will be $\text{1 mL}$. This means that your goal here is to figure out the mass of $\text{1 mL}$ of carbon dioxide.

Now, you know that the mass of $\text{100 mL}$ of carbon dioxide is equal to $\text{0.196 g}$.

You can find the density of carbon dioxide by dividing the mass of the sample by the total volume it occupies

$\rho = \text{0.196 g"/"100 mL}$

since this will get you the mass of $\text{1 mL}$ of carbon dioxide

$\rho = \text{0.196 g"/(100 * "1 mL") = "0.196 g"/100 * 1/"1 mL}$

$= \text{0.00196 g" * 1/"1 mL" = "0.00196 g"/"1 mL}$

$= \textcolor{\mathrm{da} r k g r e e n}{\underline{\textcolor{b l a c k}{{\text{0.002 g mL}}^{- 1}}}}$

The answer must be rounded to one significant figure, the number of sig figs you have for the volume of the sample.

You can thus say that $\text{1 mL}$ of carbon dioxide has a mass of $\text{0.002 g}$.

SIDE NOTE We usually express the density of a gas in grams per liter, ${\text{g L}}^{- 1}$.

In your case, the density of carbon dioxide in grams per liter is equal to

$0.002 \textcolor{w h i t e}{.} {\text{g"/(1color(red)(cancel(color(black)("mL")))) * (10^3color(white)(.)color(red)(cancel(color(black)("mL"))))/"1 L" = "2 g L}}^{- 1}$

This is very close to the density of carbon dioxide at STP conditions

https://en.wikipedia.org/wiki/Carbon_dioxide