Question

How many moles of `Ca(NO_3)_2` are there in 75 mL of 0.25 M solution?

Answer 1

`0.019` `"mol Ca(NO"_3")"_2`

Explanation:

We're asked to find the number of moles of calcium nitrate are in `75` `"mL"` of a `0.25` molar solution of `"Ca(NO"_3")"_2`.

To solve this equation, we can use the molarity equation:

`"molarity" = "moles solute"/"liters solution"`

We need the solution's volume to be in `"L"`, so let's convert it:

`75cancel("mL")((1color(white)(l)"L")/(10^3cancel("mL"))) = 0.075` `"L"`

We're asked to find the number of moles, so

`"moles solute" = ("molarity")("liters solution")`

`"mol Ca(NO"_3")"_2 = (0.25"mol"/(cancel("L")))(0.075cancel("L"))`

`= color(red)(0.019` `color(red)("mol Ca(NO"_3")"_2`

rounded to two sig figs.

Therefore, there are `color(red)(0.019` `sfcolor(red)("moles of calcium nitrate"` in `75` `"mL"` of a `0.25M` solution.