Question

Question #5d2fc

Answer 1

`"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")`