# How many moles of potassium chloride, KCl, are needed to make 100.0 mL of a 2.0 M KCl solution?

##### 1 Answer

#### Explanation:

The thing to remember about a solution's **molarity** is that you can express it as a fraction that has

In your case, a **moles** of potassium chloride, the solute, for every

#"2.0 M" = "2.0 moles KCl"/"1 L solution"#

Now, you should know that

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

This means that you can rewrite the molarity of the solution as

#"2.0 M" = "2.0 moles KCl"/(10^3color(white)(.)"mL solution")#

So, you need to figure out how many moles of potassium chloride must be dissolved in water to make

In other words, you must find the number of moles that when dissolved in **equivalent** to **moles** dissolved in

#(color(blue)(?)color(white)(.)"moles KCl")/"100.0 mL solution" = "2.0 moles KCl"/(10^3color(white)(.)"mL solution")#

Solve this equation to find

#color(blue)(?) = (100.0 color(red)(cancel(color(black)("mL solution"))))/(10^3color(red)(cancel(color(black)("mL solution")))) * "2.0 moles"#

#color(blue)(?) = "0.20 moles" -># rounded to twosig figs

Therefore, you can say that if you dissolve **moles** of potassium chloride in enough water to make