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Science 20

Science 20. Unit A: Chemistry Topic: Calculating Concentrations. Do Now. Why is a molecular molecule a non-electrolyte?. The Plan. Use math to calculate concentrations. We will learn three methods to communicate concentration-Today focus on percent by volume.

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Science 20

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  1. Science 20 Unit A: Chemistry Topic: Calculating Concentrations

  2. Do Now • Why is a molecular molecule a non-electrolyte?

  3. The Plan • Use math to calculate concentrations. • We will learn three methods to communicate concentration-Today focus on percent by volume. I can compare, explain, and calculate concentration in percent by volume (%V/V).

  4. Assignment • Page 39 #1, 2, 3, 4.

  5. ANSWERS # 1 a. Concentration is the ratio of the quantity of solute to the quantity of solution. b. A concentrated solution is a solution containing a high ratio of solute to solution. c. A dilute solution is a solution containing a low ratio of solute to solution. d. The qualitative properties of a solution are the basic attributes of a solution that can be observed with one or more of the five senses. e. The collision-reaction theory states that chemical reactions occur due to the collision and rearrangement of particles.

  6. ANSWERS # 2 Concentrated solutions demonstrate greater colour intensity, higher conductivity, and other physical characteristics compared to dilute solutions.

  7. ANSWERS # 3 At higher concentrations, more reactant particles are present in the solution. An increased number of particles increases the probability of collisions occurring between reactant particles. With a greater number of collisions, there is a greater probability of forming new bonds and product(s).

  8. ANSWERS # 4 Water will dilute the poison in the stomach and intestinal tract, hopefully decreasing the effect of the poison on cells or decreasing the speed of its absorption into the bloodstream.

  9. Did You Know? A concentrated solution of acetic acid would hurt you. However, vinegar is a 5% solution of acetic acid!

  10. Commercial Solutions Manufacturers make sure that the ratio of solute to solvent is safe & appropriate for the application.

  11. Unintended Ingredient-PCBs The solute may be an unintended ingredient. Polychlorinated biphenyls (PCBs) may be found in fish. Strict guidelines.

  12. Definitions Concentration • The ratio of quantity of solute to the quantity of solution. Concentrated Solution • A solution containing a high ratio of solute to solution Dilute Solution • A solution containing a low ratio of solute to solution.

  13. Calculating Concentration • Three methods to communicate concentration • 1) Percent by volume (% V/V) • 2) Parts per million (ppm) • 3) Molar Concentrations

  14. Calculating Concentration • Three methods to communicate concentration • 1) Percent by volume (% V/V) • 2) Parts per million (ppm) • 3) Molar Concentrations

  15. Percent by Volume (% v/v) • This is commonly used for liquids dissolved in liquids. Typically you will see it in products like drinks and cleaners. • Calculated by taking volume of solute and dividing it by the volume of solution and multiplying it by 100. • % by volume of solute = volume of solute(mL) x 100% volume of solution (mL) • Note: the volume of solution is equal to the volume of solute plus the volume of the solvent.

  16. Percent by Volume (% v/v) E.g. #1, Calculate the percent by volume of ethanol in a disinfectant if one mixed 20.0 mL of ethanol with enough water to make 2.0L. • volume of solute = 20.0 mL • volume of solution = 2000 mL • % by volume = V solute x 100% V solution =20.0mL x 100 % 2000 mL = 1.00% The solution is 1.00% ethanol by volume.

  17. Percent by Volume (% v/v) E.g., #2 • A hair product requires you to combine 20.0 mL of hydrogen peroxide with enough water to produce a solution with a total volume of 120.0 mL. Determine the percent by volume concentration of the solution.

  18. Percent by Volume (% v/v) • V solute = 20.0 mL • V solution = 120.0 mL (% V/V) = V solutex 100% V solution = 20.0 mLx 100% 120.0 mL = 16.7%*watch sig. digs

  19. Percent by Volume (% v/v) E.g., #3 • A mosquito repellent says that DEET makes up 45.0% of the total volume. If you have a 75 mL sample of this repellent, determine the volume of DEET within the sample.

  20. Percent by Volume (% v/v) • (% V/V) = 45.0% • V solution = 75 mL • V solute = ? *You will need to manipulate the formula V solute = (% V/V) x V solution 100% = 45.0% x 75 mL 100% = 33.75 mL = 34 mL* watch sig. digs.

  21. Percent by Volume (% v/v) E.g., #4 • Insecticidal soap is an environmentally friendly way to control insect pests on plants. A gardener needs a solution with a percent by volume concentration of insecticidal soap of 5.0%. If the total volume of the solution was 4000 mL, calculate the volume of insecticidal soap needed to make this solution.

  22. Percent by Volume (% v/v) • (% V/V) = 5.0% • V solution = 4000 mL • V solute = ? V solute = (% V/V)x V solution 100% = 5.0 % x 4000 mL 100% = 200 mL = 2.0 x 102 mL

  23. Assignment • Worksheet (p. 13 and 14 of workbook)

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