# Question a2e9d

Jan 28, 2017

${\text{1.3 g mL}}^{- 1}$

#### Explanation:

In order to be able to calculate the density of the liquid, you must know two things

• the mass of the sample used to fill the flask
• the volume this sample occupies

The problem provides you with the volume of the liquid

$V = \text{6.98 mL}$

so all you have to do now is figure out the mass of this sample. You know that you have

${m}_{\text{liquid" + m_"flask" = "185.4 g}}$

and that the mass of the empty flask is equal to

${m}_{\text{flask" = "176.5 g}}$

This means that you can get the mass of the liquid by subtracting the mass of the empty flask from the mass of the flask + liquid.

m_"liquid" = color(red)(cancel(color(black)(m_"flask"))) + m_"liquid" - color(red)(cancel(color(black)(m_"flask")))

${m}_{\text{liquid" = "185.4 g" - "176.5 g" = "8.9 g}}$

The density of the liquid, $\rho$, is equal to the mass of exactly one unit of volume of this liquid, so divide the total mass of the sample by its total volume to get

rho = "8.9 g"/"6.98 mL" = color(darkgreen)(ul(color(black)("1.3 g mL"^(-1))))#

The answer will have two sig figs because the mass of the liquid has two sig figs.

$\text{185.4 g" - "176.5 g" = "8.9 g} \to$ one decimal place of precision, two sig figs