Solutions Brown, T., E. LeMay, and B. Bursten. 2000. Chemistry: The Central Science. 8th ed. Phils: Pearson Education Asia Pte. Ltd. p. 469 “Most of the materials that we encounter in everyday life are mixtures of pure substances.” Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill. p. 467 “Most chemical reactions take place, not between pure solids, liquids, or gases, but among ions and molecules dissolved in water or other solvents.”

A solution is a mixture that has no visible boundaries among its components (i.e. a homogeneous mixture) Vinegar: water + acetic acid (+ others) Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill. p. 861 “A homogeneous mixture (also a solution) is a mixture that has no visible boundaries among its components.” Brown, T., E. LeMay, and B. Bursten. 2000. Chemistry: The Central Science. 8th ed. Phils: Pearson Education Asia Pte. Ltd. p. 469 Homogeneous mixtures have “components that are uniformly intermingled on a molecular level.” Brass: copper + zinc Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill. http://www.thekitchn.com/thekitchn/good-questions/what-can-i-do-with-datu-puti-filipino-coconut-vinegar-good-questions--119557 http://www.ehow.com/about_6369891_brass-alloy-information.html

The components of a solution may either be solid, liquid, or gas Resulting solution example gas air liquid soda water (CO2 in H2O) solid H2 in palladium ethanol in water sugar in water silver in gold Brown, T., E. LeMay, and B. Bursten. 2000. Chemistry: The Central Science. 8th ed. Phils: Pearson Education Asia Pte. Ltd. p. 469 “Each of the substances in a solution is called a component of the solution.” Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill. p. 468 “Since this definition places no restriction on the nature of the substances involved, we can distinguish [different types of] solutions, depending on the original states (solid, liquid, or gas) of the solution components.” Brown, , E. LeMay, and B. Bursten. 2000. Chemistry: The Central Science. 8th ed. Phils: Pearson Education Asia Pte. Ltd. Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.

A solution contains a solvent and solute(s): The solvent is present in larger amount, while the solute(s) is/are present in smaller amount/s Solution Solvent Solute soft solder (s) Pb Sn softdrinks (l) H2O sugar, CO2, etc air (g) N2 O2, Ar, etc Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.

A molecular view of the solution process

When salt is placed in a glass of water, it dissolves http://img.webmd.com/dtmcms/live/webmd/consumer_assets/site_images/articles/health_tools/sore_throat_slideshow/photolibrary_photo_of_salt_sprinkled_into_water.jpg

When the solute dissolves in the solvent, particles of the solute disperse throughout the solvent solvent-solvent interaction solute-solute interaction Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill. p. 469 “The intermolecular attractions that hold molecules together in liquids and solids [intermolecular forces of attraction] also play a central role in the formation of solutions. When one substance (the solute) dissolves in another (the solvent), particles of the solute disperse throughout the solvent. The solute particles occupy positions that are normally taken by solvent molecules. The ease with which a solute particle replaces a solvent molecule depends on the relative strengths of three types of interactions: solvent-solvent interaction, solute-solute interaction, solvent-solute interaction.” “For simplicity, we can imagine the solution process taking place in three distinct steps. Step 1 is the separation of solvent molecules, and step 2 entails the separation of solute molecules…In step 3 the solvent and solute molecules mix.” solvent-solute interaction remember your IMFAs! Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.

To determine if a solution will form, the three types of interaction are considered solvent-solvent attraction solute-solute attraction & solute-solvent attraction > solution process unfavorable < solution process favorable Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.

Effect of temperature on solubility (water solvent, gas solute)

Solubility is the amount of solute that dissolves in a fixed amount of solvent at a given temperature i.e. solubility of NaCl at 100°C = 39.12 g/100 mL H2O 20.00 g NaCl + 100 mL H2O 39.12 g NaCl + 100 mL H2O 40.00 g NaCl + 100 mL H2O Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.

Gas solubility in water decreases with increasing temperature There are relatively weak IMFAs between gas and water When temperature rises, the gas molecules get enough energy to overcome the weak IMFAs The gas molecules leave the solution Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill.

During many industrial processes, large amounts of water are taken from a nearby river or lake, pumped through the system to cool materials, and then returned to the water body at a higher temperature http://www.earthscienceworld.org/images/search/results.html?Keyword=Thermal%20Pollution#null “Here at Westport, Kentucky the Ohio River provides the large amount of water required by this coal-fired power plant. Thermal pollution is abated by the use of the large cooling tower which emits only steam into the atmosphere. The emission of the smokestack is largely steam but still contains pollutants.” Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill. p. 411 “One way to lessen the problem is with cooling towers, which lower the temperature of the water before it exits the plant.” Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill. http://www.earthscienceworld.org/images/search/results.html?Keyword=Thermal%20Pollution#null

The reduced solubility of O2 gas in hot water has a direct bearing on thermal pollution, which is the heating of waterways to temperatures that are harmful to its living inhabitants increase in water temperature accelerates fish’s metabolism fish’s need for oxygen increases supply of oxygen decreases Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill. p. 476 “It is estimated that every year in the United States some 100,000 billion gallons of water are used for industrial cooling, mostly in electric power and nuclear power production. This process heats the water, which is then returned to the rivers and lakes from which it was taken. Ecologists have become increasingly concerned about the effect of thermal pollution on aquatic life. Fish, like all other cold-blooded animals, have much more difficulty coping with rapid temperature fluctuation in the environment than humans do. An increase in water temperature accelerates their rate of metabolism, which generally doubles with each 10°C rise. The speedup of metabolism increases the fish’s need for oxygen at the same time that the supply of oxygen decreases because of its lower solubility in heated water. Effective ways to cool power plants while doing only minimal damage to the biological environment are being sought.” Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill. http://www.dec.ny.gov/animals/32847.html

Effect of pressure on solubility (water solvent, gas solute)

Gas solubility in water increases with increasing pressure Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill. p. 411 “A. A saturated solution of a gas is in equilibrium at pressure P1 If the pressure is increased to P2, the volume of the gas decreases. Therefore, the frequency of collisions with the surface increases As a result, more gas is in solution when equilibrium is re-established.” P1 at equilibrium P2 is applied P2 at equilibrium Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill.

Gas solubility in water increases with increasing pressure At a given pressure, the same number of gas molecules enter and leave the solution (that is, the system is at equilibrium) If the pressure increases, gas particles collide with the liquid surface more often More gas particles enter than leave the solution per unit time, thereby increasing the solubility of the gas Silberberg, M. 2010. Principles of General Chemistry. 2nd ed. New York: McGraw-Hill.

The effect of pressure on solubility is seen when one opens a bottle of a carbonated beverage (champagne, beer, or soft drinks) carbonated beverage is bottled under a CO2 pressure greater than atmospheric pressure when the bottle is opened, CO2 pressure above the solution is decreases CO2 solubility decreases CO2 bubbles out of solution Brown, , E. LeMay, and B. Bursten. 2000. Chemistry: The Central Science. 8th ed. Phils: Pearson Education Asia Pte. Ltd. Chang, R. 2002. Chemistry 7th ed. Singapore: McGraw-Hill.

Expressing Concentration Concentration is the amount of solute in a given amount of solution. - Percent (% w/w, %v/v) - parts per million (ppm), parts per billion (ppb), parts per trillion (ppt) - Molarity (moles/L)

A typical aspirin tablet contains 300 A typical aspirin tablet contains 300. mg of the active ingredient, acetylsalicylic acid. What is the average concentration, expressed as percentage by weight (% w/w), of acetylsalicylic acid in the body of a 165-pound person who has just taken two aspirin tablets. Assume all of the aspirin dissolves. Iodized salt may be prepared by mixing in a small amount of potassium iodide in table salt (7.6 x 10-5 g of KI per gram of table salt). What is the concentration of KI in iodized salt expressed in ppm?

The maximum permitted level of mercury in drinking water is 0. 002 ppm The maximum permitted level of mercury in drinking water is 0.002 ppm. Analysis of 250.-mL sample of tap water was found to contain 0.550 moles of Hg. Is this water supply safe for human consumption? The Safe Drinking Water Act of 1974 (US) sets a maximum of 160. mg of sodium per liter of drinking water. What is the maximum molarity of sodium chloride permitted in community drinking water?

Dilution Solutions may be labeled as dilute or concentrated. Dilute solutions have low concentrations of solute while concentrated solutions have higher concentrations.

In dilution, the amount (moles) of solute DOES NOT change In dilution, the amount (moles) of solute DOES NOT change. Only the concentration is decreased. C1V1=C2V2