Question

What is the molarity of a solution in which 10.0g of `AgNO_3` is dissolved in 500. mL of solution?

Answer 1

`"0.118 M"`

Explanation:

Molarity is simply a measure of the concentration of a solution in terms of how many moles of solute are present per liter of solution.

`color(blue)(|bar(ul("molarity" = "moles of solute"/"liters of solution"))|)`

This means that in order to find a solution's molarity you must know two things

• the number of moles of solute present
• the volume of the solution

In order to find the number of moles of silver nitrate, `"AgNO"_3`, present in that `"10.0-g"` sample, use the compound's molar mass

`10.0 color(red)(cancel(color(black)("g"))) * "1 mole AgNO"_3/(169.87color(red)(cancel(color(black)("g")))) = "0.05887 moles AgNO"_3`

Now, do not forget that molarity is expressed per liter of solution. This means that you're going to have to convert the volume from milliliters to liters by using the conversion factor

`"1 L" = 10^3"mL"`

Plug in your values to get

`color(blue)( |bar(ul(c = n_"solute"/V_"solution"))|)`

`c = "0.05887 moles"/(500. * 10^(-3)"L") = color(green)(|bar(ul("0.118 M"))|)`

The answer is rounded to three sig figs.