Molarity, Molality, Dilution Calculations

Part I: Molarity and Molality

  • the ______of a solution can be ______in a variety of ways.
  • the words “______” and “______” can describe a sol’n ______ specific ______. These are ______ descriptions.
  • ______ descriptions of concentration (numerical values) can be ______from ______information about the solution, such as ____ of ______and either ______or ____ of ______. ______(M) and ______ (m) are two such values.
  • Molarity (M) = the number of ____ of _____per_ ____ of total solution.
  • Molarity involves a _____ amount of solute, so if you are given something like _____, you must ______them into _____ first.
  • Molarity also involves the ______(in _____) of ______, so if you are given something like ___, you must convert them into _____ first.
  • once you have ______and ______, just divide. Molarity unit = ___
  • steps in the calculation:
  1. set up a “______” that lists the info _____ in the problem, as well as which ______you are ______for (the __)
  2. decide which ______of the formula you need to _____ the problem
  3. ______units given to those needed to ______the units in the formula
  4. plug in the ______and solve!

Ex1 (Molarity): What is the Molarity of a 2.3 L solution containing 54.3 g of H3PO4?

M =

mol =

L =

  • molality(m) = the number of ____ of _____per ______of ______.
  • molality involves a _____ amount of solute, so if you are given something like ______, you must ______them into moles first.
  • molality also involves the ____ (in ______) of ______, so if you are given something like ______, you must convert them into ______first.
  • once you have ______and ______, just divide. Molality unit = ___
  • the reason we have ______ of concentration values is because of the tendency of a ______to ______or______with ______or ______fluctuations.
  • this affects the ______ of the liquid, which, in turn, affects the ______ value.
  • therefore, if the temperature or pressure ______, Molarity is used as the ______of concentration.
  • however, molality does ___ involve ______, it involves ____ (in ___), which does not fluctuate with ______in temperature or pressure.
  • therefore, if the temperature/pressure ______, ______is used as the measure of concentration.

Ex2 (molality): How many grams of NaCl were added to 1.48 kg of ethanol if the resulting solution was 3.7 m?

m =

mol =

kg =

Part II: Dilution Calculations

  • most ____, _____, and other chemical ______are sold in very ______form to save on ______and ______(smaller ______and ____). (Think of frozen concentrated ______.)
  • however, most ______call for very ______versions of these solutions.
  • to ______a solution, you combine ______with the ______solution until the proper, _____-concentration solution is formed.
  • there are ____ parts to the dilution equation:
  1. MD = ______of the ______ (or ______) solution
  2. MC = ______of the ______ (or ______) solution
  3. VD = ______of the ______ (or ______) solution
  4. VC = ______of the ______ (or ______) solution
  • in most cases, you need to calculate ___, the _____ of the conc. sol’n, so the formula will need to be ______ like this:
  • in addition to the VC, you will also need to know the ______of distilled ____ to use to ______the concentrated solution. You can calculate this volume of water by using this equation:

Ex3 (Dilution): How many mL of 12 M HCl is needed to produce 1.5 L of a solution that is 3.8 M? Also, how many mL of distilled water must be used to make this 3.8 M solution?

MD =

MC =

VD =

VC =

VW =