Question

Question #5b32a

Answer 1

Molarity represents the concentration of as solution expressed in number of moles of solute per liter of solution.

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

So, let's say you want to make a solution of sucrose (table sugar - `C_12H_22O_11`), so you add 15 g of sucrose to 500.0 mL of water.

You first determine the number of moles of solute - in this case, sucrose:

`n_(sucrose) = ("mass")/(" molar mass") = (15.0g)/(246 g/(mol)) = 0.061` moles

Therefore, your solution's molarity will be

`C = (0.061 "moles")/(500.0 * 10 ^(-3) L) = 0.12` `"moles/L"`

Notice that I've converted mL to L.

As a strategy, always try to determine how much of something - number of moles - is added to what volume of solution.

You can find other examples here

http://socratic.org/questions/how-do-you-find-molar-it-s-give-three-examples?source=search