Question #5d2fc

1 Answer
Jan 25, 2016

Answer:

#"42 g"#

Explanation:

Think about what the density of a substance tells you.

As you know, the density of a substance is defined as the mass of one unit of volume of that substance.

#color(blue)("density" = "mass"/"unit of volume"#

In your case, the volume is given in milliliters, and the density in grams per milliliter, so one unit of volume will be equal to #"1 mL"#.

A density of #"0.79 g/mL"# will thus tell you that you get #"0.79 g"# for every #"1 mL"# of ethanol.

So, you can say that

#"1 mL " -> " 0.79 g"#

#"2 mL " -> " 0.79 g" + "0.79 g"#

#"3 mL " -> " 0.79 g" + "0.79 g" + "0.79 g"#
#vdots#

and so on. In your case ,the sample of ethanol is said to have a volume of #"53 mL"#. This means that its mass will be equal to

#53 color(red)(cancel(color(black)("mL"))) * overbrace("0.79 g"/(1color(red)(cancel(color(black)("mL")))))^(color(purple)("given density")) = "41.87 g"#

Rounded to two sig figs, the answer will be

#m = color(green)("42 g")#