# Calculate the molarity of the solute in a solution containing 14.2 KCl in 250 mL solution?

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I know molarity is (moles of the solute/ liters of the solution)

The issue I dont understand is the 14.2 KCl I dont know what the units are. I am assuming its not grams

I know molarity is (moles of the solute/ liters of the solution)

The issue I dont understand is the 14.2 KCl I dont know what the units are. I am assuming its not grams

##### 1 Answer

#### Explanation:

I would say that you're dealing with a solution that contains **grams** of potassium chloride,

If this is the case, your strategy here will be to use the **molar mass** of potassium chloride to calculate how many *moles* are present in the sample

#14.2 color(red)(cancel(color(black)("g"))) * "1 mole KCl"/(74.55color(red)(cancel(color(black)("g")))) = "0.1905 moles KCl"#

Now, **molarity** is simply a measure of a solution's *concentration* in terms of how many moles of solute it contains **per liter of solution**.

This means that in order to find a solution's molarity, you essentially must figure out how many moles of solute you have in

In your case, you know that **moles**.

All you have to do now is *scale up* this solution so that its volume becomes **four times as many moles** of solute.

#1 color(red)(cancel(color(black)("L solution"))) * "0.905 moles KCl"/(1/4color(red)(cancel(color(black)("L solution")))) = "0.76 moles KCl"#

So, if **moles** of solute, it follows that its molarity is

#"molarity" = color(green)(|bar(ul(color(white)(a/a)color(black)("0.76 mol L"^(-1))color(white)(a/a)|)))#

The answer is rounded to two **sig figs**, the number of sig figs you have for the volume of the solution.