Science 20 - Solution concentration

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Science 20 - Solution concentration The concentration of a solution is a ratio of the amount of solute dissolved in a specific quantity of solvent.

1 Science 20 - Solution concentration The concentration of a solution is a ratio of the amount of solute dissolved in a specific quantity of solvent. A dilute solution contains a relatively low quantity of solute. A concentrated solution contains a relatively high quantity of solute. CONCENTRATED DILUTE Concentrated solutions usually react faster or more violently that dilute solutions, because concentrated solutions contain a greater amount of solute (chemical) The collision-reaction theory states that all chemical reactions involve collisions between atoms, ions or molecules. A solution having a greater concentration of solute to solution reacts faster than a more dilute solution. This occurs for the following reasons: o A chemical reaction is a result of collisions between particles. o A concentrated solution has more particles of solute available for possible collisions than a dilute solution. o The probability of collisions increases as the number of solute particles within a system increases. Concentrated solution: more particles means more collisions more often. Dilute solution: less particles means less collisions less often. There are three common ways to express the concentration of a solution. Each method has a different purpose: Symbol Formula Use Used by Percent by volume % v/v 100% Communicating the volume of a liquid solute dissolved in the total volume of solution Manufacturers of commercial and household products. Parts per million ppm Communicating 10 levels of a substance like pollution in very dilute solutions Government environmental and health agencies Molar concentration C Communicating mole amounts of chemicals in a solution Scientists Science 20 Lesson 1-02 Page 1

2 Percent by volume (% v/v) Formula: % = 100% Percent by volume (%V/V) examples Example problem 1 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 ml. Calculate the percent by volume concentration of the solution. Example problem 2 A mosquito repellent says that the chemical DEET makes up 45.0 % of the total volume of the solution. If you have a 75.0 ml sample of this repellent, determine the volume of DEET within the sample. Example problem 3 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 this solution is 4000 ml, calculate the volume of insecticidal soap needed to make this solution. Science 20 Lesson 1-02 Page 2

3 Parts per million concentration This method is used for very small concentrations like toxic chemicals in the environment. The term parts per million means one part solute for every million parts of solution. Formula: = 10 Example problem 1 A 200 g sample from a bottle of water contains 5.4 x 10-3 g of mercury. Calculate the concentration of the mercury in parts per million. Example problem 2 Carbon monoxide, CO (g), is a deadly gas that takes the place of oxygen molecules in your blood. If you are smoking, the concentration of carbon monoxide that reaches your lungs is 200 ppm. Determine the mass of carbon monoxide gas that is found in a sample of air having a mass of 9.6 g (about one breath). Science 20 Lesson 1-02 Page 3

4 Science 20 Solution properties, %v/v concentration and ppm 1. Water is a good medium for chemical change because it A. helps the solute mix uniformly B. breaks the bonds of the solute(s) C. allows new bonds to form, allowing for new substances D. all of the above 2. Cobalt(II) nitrate is dissolved in water. The cobalt(ii) nitrate is considered to be the A. product B. solution C. solvent D. solute 3. Water is an effective solvent for ionic compounds because A. each water molecule has a negative end and a positive end B. water and ionic compounds have the same charge C. ionic compounds have a negative charge D. water has a negative charge 4. Match each description with the appropriate term listed. Place your answer in the blank space given. i. solute ii. exothermic change iii. non-electrolyte iv. solvent v. solution vi. chemical change vii. dissociation viii. endothermic change ix. aqueous solution x. electrolyte a. a substance in a solution that breaks down the bonds of a solute; a substance that does the dissolving and is in greater proportion in the mixture b. a solute that forms a solution that conducts electricity c. a change in which one or more new substances with different properties are formed d. a homogeneous mixture of dissolved substances that contains a solute and a solvent e. a chemical change in which energy is absorbed from the surroundings f. a solution in which water is the solvent g. the separation of an ionic compound into individual ions in a solution h. a chemical change in which energy, usually in the form of heat, is released into the surroundings i. a substance in a solution whose bonds are broken by a solvent; a substance that dissolves j. a solute in a solution that does not conduct electricity Science 20 Lesson 1-02 Page 4

5 5. A concentrated solution is one that has A. no solvent B. more solute than solvent C. a high ratio of solute to solvent D. a low ratio of solute to solvent 6. Which is not a reason why a solution with a greater concentration reacts faster than a solution that is more dilute? A. A chemical reaction is a result of collisions between particles. B. A dilute solution has more particles of solute available for collisions than a concentrated solution. C. A concentrated solution has more particles of solute available for collisions than a dilute solution. D. The probability of collisions increases as the number of solute particles within a system increases. 7. Decide whether each statement is true (T) or false (F). a. The carbonated water in fountain pop is the solute. b. A theory stating that chemical reactions involve the collision and rearrangement of particles is known as qualitative reaction theory. c. A solution that contains a low ratio of solute to solvent is a dilute solution. d. The ratio of quantity of solvent to quantity of solution is the concentration of a solution. 8. For which calculation could the following formula used? 100% A. molar concentration B. parts per million C. percent by volume D. percent of solvent 9. A bottle of insect repellent states that the percent by volume concentration of DEET is 14%. Calculate the volume of DEET in a 500-mL container. A. 35 ml B. 70 ml C. 140 ml D. 500 ml 10. Which concentration measurement is used for very dilute solutions? A. percent by volume B. parts per million C. moles per litre D. milligrams per litre Science 20 Lesson 1-02 Page 5

6 11. A gardener requires 2000 ml of insecticidal soap solution with a concentration of 7.0% by volume. The volume of insecticidal soap needed is A. 3.5 x 10 1 ml B. 1.4 x 10 2 ml C. 2.0 x 10 3 ml D. 1.4 x 10 4 ml 12. Calculate the percent solution by volume (%V/V) when 50.0 ml of ethanol is diluted to 140 ml with water. 13. Calculate volume of ethylene glycol (in ml) needed to make 4.00 L of automotive antifreeze, which is a 60.0 % (by volume) solution. 14. a) Determine volume of liquid isopropyl alcohol needed to prepare 500 ml of a 70.0% (by volume) solution. Science 20 Lesson 1-02 Page 6

7 b) What is the volume of water that you need to add to the alcohol to make the 500 ml of solution? Science 20 Lesson 1-02 Page 7

Solutions and Concentrations

A02 Solutions and Concentration.notebook Solutions and Concentrations What is concentration? 1 The difference between concentrated solutions and dilute solutions can be determined qualitatively and quantitatively.