Question

Question #bd6f7

Answer 1

`2.48 * 10^(22)`

Explanation:

Start by converting the sample of nitric acid from grams to moles by using the compound's molar mass

`M_("M HNO"_3) = color(blue)("63.01 g")color(white)(.) color(brown)("mol"^(-1))`

This tells you that `color(brown)("1 mole")` of nitric acid has a mass of `color(blue)("63.01 g")`.

In your case, the sample of nitric acid will contain

`2.59 color(red)(cancel(color(black)("g"))) * "1 mole HNO"_3/(63.01color(red)(cancel(color(black)("g")))) = "0.0411 moles HNO"_3`

To convert the number of moles to molecules, use Avogadro's constant

`color(purple)(ul(color(black)("1 mole HNO"_3 = 6.022 * 10^(23)"molecules HNO"_3)))`

In your case, you will have

`0.0411 color(red)(cancel(color(black)("moles HNO"_3))) * (6.022 * 10^(23)"molecules HNO"_3)/(1color(red)(cancel(color(black)("mole HNO"_3))))`

`= color(darkgreen)(ul(color(black)(2.48 * 10^(22)"molecules HNO"_3)))`

The answer is rounded to three sig figs.