Molarity v Molality
Molarity
Number of Solutes in one liter of solution M = Moles of Solute Volume of solution Ex. If you have 3.5L of solution and 90 grams of NaCl, what is the molarity? Convert 90g to moles 90gNaCl | 1 mole = 1.54 moles | 58.43 g Divide 1.54 by 3.5 1.54 = 0.4M 3.5 |
Molality
Moles of Solute per kilogram of solvent m = Moles of Solute kg of Solvent Ex. 17.1 grams of sucrose are dissolved in 125 grams of water. Find Molality. Convert 17.1g to moles 17.1g C12H22O11| 1 mole = 0.05 | 342 g Convert 125g to kg 125g| 1 kg = 0.125kg | 1x10^3 Divide 0.05 by .125 0.05 = 0.400m .125 |
Dilution
Dilution is when water is added to acids to reach a desired concentration.
The formula is M1 x V1 = M2 x V2
Molarity1 x Volume1 = Molarity2 x Volume 2
Ex. To what volume should 25mL and 15M of nitric acid be diluted to prepare a 3.0M solution?
M1- 15 15(25) = 3(V2) Multiply
V1- 25 375 = 3V2 Divide by Coefficient
M2- 3.0 3 3
V2- ? 125mL = V2 Solve
Dilution is when water is added to acids to reach a desired concentration.
The formula is M1 x V1 = M2 x V2
Molarity1 x Volume1 = Molarity2 x Volume 2
Ex. To what volume should 25mL and 15M of nitric acid be diluted to prepare a 3.0M solution?
M1- 15 15(25) = 3(V2) Multiply
V1- 25 375 = 3V2 Divide by Coefficient
M2- 3.0 3 3
V2- ? 125mL = V2 Solve