Question

Question #a9226

Answer 1

`"19 g"`

Explanation:

The density of a substance tells you the mass of exactly one unit of volume of that substance. Simply put, the density of a substance provides you with a conversion factor that can be used to go from mass to volume or vice versa.

In this case, the liquid is said to have a density of `"0.775 g mL"^(-1)`, which means that you get `"0.775 g"` for every `"1 mL"` of this liquid.

`color(darkorange)("0.775 g")color(white)(.) color(blue)("mL"^(-1)) -> color(darkorange)("0.775 g") color(white)(.) "for every" color(white)(.) color(blue)("1 mL") color(white)(.)"of liquid"`

Now, you know that your sample has a volume of `"25 cm"^3`. Keep in mind that

`color(blue)(ul(color(black)("1 mL" = "1 cm"^3)))`

You can thus use the density of the liquid as a conversion factor to find the mass of the sample

`25 color(red)(cancel(color(black)("cm"^3))) * (1color(red)(cancel(color(black)("mL"))))/(1color(red)(cancel(color(black)("cm"^3)))) * "0.775 g"/(1color(red)(cancel(color(black)("mL")))) = color(darkgreen)(ul(color(black)("19 g")))`

The answer is rounded to two sig figs, the number of sig figs you have for the volume of the sample.