Question #a9226

1 Answer
Feb 16, 2017


#"19 g"#


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.