1 / 12

Molarity and Molality

Molarity and Molality. Molarity ( M ). number of moles of solute (n) per liter (L) of solution Molarity ( M ) = Moles of Solute Liters of Solution Note: Moles = Mass of Solute Molar Mass of Solute.

rollo
Download Presentation

Molarity and Molality

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Molarity and Molality

  2. Molarity (M) number of moles of solute (n) per liter (L) of solution Molarity (M) = Moles of Solute Liters of Solution Note: Moles = Mass of Solute Molar Mass of Solute

  3. 1. What is the molarity of the solution if 3.0 mole of solute is dissolved in 12.0 L solution? Given: Moles of Solute – 3.0 mole Liters of Solution – 12.0 L Formula: Molarity = Moles of Solute Liters of Solution Answer: M = Moles of Solute Liters of Solution = 3.0 mole 12.0L = 0.25 M

  4. 2. What is the molarity of a 400.0 mL solution containing 8.0 g NaOH? Given: Mass of Solute – 8.0 g of NaOH Liters of Solution – 400.0 mL Formula: Molarity = Moles of Solute Liters of Solution Answer: Moles = Mass of Solute Molar Mass of Solute = 8 g of NaOH (23+16+1g/mole) = 8 g NaOH 40 g/mole = 0.2 mole

  5. Given: Molarity - ? Liters of Solution – 400.0 mL Moles of Solute – 0.2 mole Formula: Molarity = Moles of Solute Liters of Solution Answer: M = Moles of Solute Liters of Solution = 0.2 mole 0.4 L = 0.5 M = 400mL X 1 L 1000mL = 0.4L

  6. 3. How many grams of Ca(OH)2 are needed to prepare an 800.0 mL solution of 0.015 M concentration? Given: Molarity – 0.015 M Liters of Solution – 800.0 mL Formula: Molarity = Moles of Solute Liters of Solution Answer: Moles = (Molarity) (Liters of Sol’n) = 0.015 M (0.8 L) = 0.012 moles = 800mL X 1 L 1000mL = 0.8L

  7. Given: Mass of Solute – ? Moles of Solute – 0.012 mole Molar Mass – Ca(OH)2 = [40+([16x2]+[1x2])] = 74g/mole Formula: Moles = Mass of Solute Molar Mass of Solute Answer: Moles = Mass of Solute Molar Mass of Solute Mass of Solute = (Moles) (Molar Mass of Solute) = (0.012moles) (74g/mole) = 0.89 g

  8. Molality (m) as the number of moles of solute (n) per kilogram (kg) of solution Molality (m) = Moles of Solute Kilograms of Solvent Note: Moles = Mass of Solute Molar Mass of Solute

  9. 1. What is the molality of a solution containing 0.46 mole of solute in 2.0 kg water? Given: Moles of Solute – 0.46 mole Kilogram of Solvent – 2.0 kg Formula: Molality = Moles of Solute Kilogram of Solvent Answer: m = Moles of Solute Kilogram of Solvent = 0.46 mole 2.0kg = 0.23 m

  10. 2. What is the molality of a solution containing 75.5 g Pb(NO3)2 in 400.0 g water? Given: Mass of Solute – 75.5 g Pb(NO3)2 Molar Mass = [207+([14]2)+([16]6)] = 331 g/mole Formula: Moles = Mass of Solute Molar Mass of Solute Answer: Moles = Mass of Solute Molar Mass of Solute = 75.5 g 331 g/mole = 0.23 moles

  11. Given: Molality – ? Moles of Solute – 0.23 moles Kilogram of Solvent – 400.0 g = 0.4kg Formula: m = Moles of Solute Kilogram of Solution Answer: m = Moles of Solute Kilogram of Solution = 0.23 moles 0.4 kg = 0.58 m

  12. What mass of solute is needed to prepare each of the following solutions? a. 1.00 L of 0.125 M K2SO4b. 375 mL of 0.015 MNaF • Calculate the molarity of each of the following solutions:a. 12.4 g KCl in 289.2 mL solution b. 16.4 g CaCl2 in 0.614 L solution   • Calculate the molality of each of the following solutions:a. 2.89 g of NaCl dissolved in 0.159 g of water b. 1.80 molKCl in 16.0 mol of H2O

More Related