What is the molarity of 2 mol of #KI# dissolved in 1 L water?

1 Answer
Stefan V.
Apr 3, 2016

#"2 mol L"^(-1)#

Explanation:

Molarity is simply a measure of concentration.

For a given solution, molarity is calculated by taking into account how many moles of solute you get per liter of solution.

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

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

  • the number of moles of solute
  • the total volume of the solution expressed in liters

In your case, you know that the solution has a volume of #"1 L"#. Since molarity tells you how many moles of solute you get in one liter of solution, the number of moles of solute present in this solution will essentially be equivalent to its molarity.

So, if you have #2# moles of potassium iodide, #"KI"#, which is your solute, in #"1 L"# of solution, you have a solution of #"2 mol L"^(-1)#, or #"2 molar"#.

#color(blue)(|bar(ul(color(white)(a/a)c = n_"solute"/V_"solution"color(white)(a/a)|)))#

This is equivalent to

#c_(KI) = "2 moles"/"1 L" = color(green)(|bar(ul(color(white)(a/a)"2 mol L"^(-1)color(white)(a/a)|)))#

So keep in mind that every time you're looking for a solution's molarity, you are essentially looking for how many moles of solute you get in one liter of solution.

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