Welcome to Chemistry

WednesdayMarch 30, 2011(??)Bell RingerWednesday, 3-30-11

When energy is added to a liquid, what phase change occurs?How much stronger is an acid at pH 4 than one at pH 6?vaporization either evaporation or boiling102 = 100 xAnnouncementsIf you have not yet taken our last test (Test 8), please see me ASAP!We will have a test this Friday.Six-Weeks Assignment ListDate IssuedDate DueWS - The Kinetic Molecular Theory and Nature of Gases2/243/3Quiz Pressure Unit Conversions3/33/3WS The Gas Laws3/33/10WS Daltons Law of Partial Pressures3/73/14WS Practice Working with Gases3/93/23TEST 83/113/11WS - Solubility3/213/28WS Types of Mixtures3/233/30WS Solute Solvent Interactions3/284/4WS Review of Important TAKS Concepts Part 13/294/1Continue WorksheetReview of Important TAKS Concepts (Part 1)Start 4

Reading a GraphHow many centimeters did these plants grow in 15 days with a 10% phosphorus fertilizer?Which % fertilizer would be the most economical for this farmer to use? Why?Start 1, 3Reading a GraphAt what volume would the pressure of nitrogen gas be 350 kPa?What happens to the pressure of nitrogen gas as the volume increases?

Analyzing a GraphHorses kept in stables sometimes chew on wood. This can lead to damage to the mouth and digestive system. The graph shows the results of a study of a medication that prevents horses from chewing on wood. Fromthe graph, what inference can be made about the effectiveness of the product?A. Most horses like the medication.B. The medication is most effective between Days 4 and 5.C. Most horses will show improvement within 7 days.D. The effects of the medication are long lasting.

Analyzing a GraphHorses kept in stables sometimes chew on wood. This can lead to damage to the mouth and digestive system. The graph shows the results of a study of a medication that prevents horses from chewing on wood. Fromthe graph, what inference can be made about the effectiveness of the product?A. Most horses like the medication.B. The medication is most effective between Days 4 and 5.C. Most horses will show improvement within 7 days.D. The effects of the medication are long lasting.TAKS Sample QuestionWhich of these is an advantage of producing electricity using solar power plants rather than using coal-fired power plants?A. Solar power plants can operate for about 10 hours per day.B. Solar power plants can produce variable amounts of energy.C. Solar power plants produce fewer pollutants.D. Solar power plants require continuous sunlight.Stop 3TAKS Sample QuestionWhich set of coefficients balances the equation?F. 3, 3, 1, 2G. 6, 1, 1, 3H. 3, 2, 1, 6J. 6, 2, 1, 6

Stop 4TAKS Sample QuestionThe transfer of heat by the movement of aircurrents in Earths atmosphere is an exampleof A. conductionB. convectionC. radiationD. fusionStop 1TAKS Sample QuestionIn photography, which of these is an exampleof a chemical change?F. Light being refracted by a camera lensG. Adjusting a lens to focus lightH. Halide granules being activated by lightJ. Allowing a certain wavelength of light into the cameraTAKS Sample QuestionSilver bromide is a type of halide. Elementsfrom which group in the periodic table arenecessary to form halide compounds?A. Group 4B. Group 5C. Group 10D. Group 17Solutes: Electrolytes and NonelectrolytesSubstances that dissolve in water are classified according to whether they yield molecules or ions in solution.When an ionic compound dissolves, the positive and negative ions separate from each other and are surrounded by water molecules.These solute ions are free to move, making it possible for an electric current to pass through the solution.A substance that dissolves in water to give a solution that conducts electric current is called an electrolyte.Solutes: Electrolytes and NonelectrolytesSodium chloride, NaCl, is an electrolyte, as is any soluble ionic compound.Certain highly polar molecular compounds, such as hydrogen chloride, HCl, are also electrolytes because HCl molecules form the ions H3O+ and Cl when dissolved in water.By contrast, a solution containing neutral solute molecules does not conduct electric current because it does not contain mobile charged particles.Solutes: Electrolytes and Nonelectrolytes

A substance that dissolves in water to give a solution that does not conduct an electric current is called a non-electrolyte.Sugar is a non-electrolyte.The picture below shows an apparatus for testing the conductivity of solutions.Solutes: Electrolytes and Nonelectrolytes

The electrodes are conductors that are attached to a power supply and that make electric contact with the test solution.For a current to pass through the light-bulb filament, the test solution must provide a conducting path between the two electrodes.Solutes: Electrolytes and Nonelectrolytes

A non-conducting solution is like an open switch between the electrodes, and there is no current in the circuit.The light bulb glows brightly if a solution that is a good conductor is tested.Such solutions contain solutes that are electrolytes.Solutes: Electrolytes and Nonelectrolytes

For a moderately conductive solution, however, the light bulb is dim.If a solution is a poor conductor, the light bulb does not glow at all.Such solutions contain solutes that are non-electrolytes.LabElectrolytes and Non-ElectrolytesWhy does saltwater conduct electrical current but sugar water does not?Bell Ringer 3-8-10

Saltwater conducts electrical current because water breaks the salt into charged ions, which conduct current. Sugar is broken down into molecules, which do not conduct current.Bell Ringer 3-8-10

Concentration of SolutionsThe concentration of a solution is a measure of the amount of solute in a given amount of solvent or solution.Some medications are solutions of drugs - a one-teaspoon dose at the correct concentration might cure the patient, while the same dose in the wrong concentration might kill the patient.The way of expressing the concentrations of solutions is molarityConcentration of SolutionsSometimes solutions are referred to as dilute or concentrated.Dilute just means that there is a relatively small amount of solute in a solvent.Concentrated means that there is a relatively large amount of solute in a solvent.Note that these terms are unrelated to the degree to which a solution is saturated a saturated solution of a substance that is not very soluble might be very dilute.MolarityMolarity is the number of moles of solute in one liter of solution.The symbol for molarity is M.To find the molarity of a solution, you must know the molar mass of the solute.MolarityEx) a one-molar solution of sodium hydroxide, NaOH, contains one mole of NaOH in every liter of solution.The concentration of a one-molar solution of sodium hydroxide is written as 1 M NaOH.One mole of NaOH has a mass of 40.0 g - if this quantity of NaOH is dissolved in enough water to make exactly 1.00 L of solution, the solution is a 1 M solution.If 20.0 g of NaOH, which is 0.500 mol, is dissolved in enough water to make 1.00 L of solution, a 0.500 M NaOH solution is produced.MolarityThis relationship between molarity, moles, and volume may be expressed in the following way:

MolarityIf twice the molar mass of NaOH, 80.0 g, is dissolved in enough water to make 1 L of solution, a 2M solution is produced.The molarity of any solution can be calculated by dividing the number of moles of solute by the number of liters of solution.Note that a 1 M solution is not made by adding 1 mol of solute to 1 L of solvent.MolarityIn such a case, the final total volume of the solution would not be 1 L.Instead, 1 mol of solute is first dissolved in less than 1 L of solvent, then the resulting solution is carefully diluted with more solvent to bring the total volume to 1 L.Sample Problem #1You have 3.50 L of solution that contains 90.0 g of sodium chloride, NaCl. What is the molarity of that solution?Sample Problem #2You have 0.8 L of a 0.5 M HCl solution. How many moles of HCl does this solution contain?MolarityLabSuper-Saturated Solutions(page 107)What is a super-saturated solution?Bell Ringer 3-10-10

A super-saturated solution is one that has more solute dissolved in it than it should have at that temperature.Bell Ringer 3-10-10

Review for Test 9Mixtures: Solutions, Colloids, and SuspensionsSolubilityElectrolytes and Non-ElectrolytesMolarity(page 109)1What type of mixture contains the smallest solute particles?solutionsWhat type of mixture contains the largest solute particles?suspensions2A student has an unknown sample of a mixture, and she wants to determine which type of mixture it is. She shines a light though the mixture and see a glow inside the container. She filters the mixture but finds no particles trapped in the filter. There is no sediment on the bottom of the container. What is most likely the identity of the mixture?a colloid3A chemistry student wants to determine the identity of a mixture. He observes that the mixture is clear and colorless, has no smell, and conducts an electric current. What is most likely the identity of this mixture?a salt water solution4If a student determines that a mixture will not conduct an electric current, what would be the best description of the solute used to make the mixture?A non-electrolyte5If a solvent breaks a solute all the way down into ions, what will certainly be a property of the mixture?The mixture will conduct electrical current.6List three properties that a solution of sugar-water will have and one property it will not have.will have:a sweet taste, be fluid in nature, and be mostly odorlesswill not have:electrical conductivity7List two examples of each of the following:elementshydrogen, oxygencompoundswater, table salthomogeneous mixturessaltwater, sugar waterheterogeneous mixturemilk, pond wateralloyssteel, brass8If a student is trying to determine the saturation point of a solid solute in a liquid solvent, what factors would he most be concerned with?the nature (identity) of the solute and solvent and the temperature of the solvent.9What is true concerning dissolving and crystallization when the saturation point of a solute in a solvent has been reached?dissolution equals crystallization10A student finds that the rate of crystallization is equal to the rate of dissolution in her mixture. As a result of this, what has her mixture reached?solution equilibrium 11A student learns that it is possible to dissolve 35.9 grams of NaCl in 100 mL of H2O when the water is 200C. If this student dissolves 18.8 grams of NaCl in 100 mL of water at 200C, what type of solution has she made?an unsaturated solution12The solubility of table sugar is listed as 204 grams in 100 mL of water at 200C. What does this mean?204 grams of sugar will dissolve in 100 mL of water if the temperature of the water is 200C to create a saturated solution.13How many grams of sodium nitrate (NaNO3) will dissolve in 100 grams of water when the water is at a temperature of 430C?about 107 grams

14Which of the solutes is most affected by a change in temperature from 0oC to 10oC?CsCl

1560 grams of KNO3 will dissolve in 100 mL of water when the water is at what temperature?about 380C

16Which of the solutes has the lowest solubility value when the temperature is 50oC?the highest?lowest: Li2SO4

highest: CsCl 17Water is a polar solvent, which means that the water molecule has a positive and negative end. Oil will not dissolve in water, but gasoline will dissolve in oil. According to this information, gasoline is made up of what type of molecules?non-polar

18List three solutes that are not soluble in water.oilgasolinefat19What factor most directly affects the solubility of a solid in a liquid?the temperature of the solvent20A fish is living in a small pond. One night in November the air temperature falls from 74oF to 43oF. The water temperature decreases as a result. What change will most likely occur in the fishs life?The colder water will now hold more oxygen gas and the fish will not have to work as hard to get enough. 21List two factors that would increase the amount of solid solute that will dissolve in a liquid solvent.Heat the solventAdd more solvent22What is the safest way to dilute concentrated sulfuric acid?add the acid to water slowly while stirring constantly.23What is the main difference between the three types of mixtures: solutions, colloids and suspensions?the size the solute particles are broken down to in the dissolving process24A Coca-Cola that fizzes when you open the bottle is an example of a _____ dissolved in a _______.

gasliquid25Give two examples of super-saturated solutions.sweet teaCO2 dissolved in a Coca-Cola26If a solution shows a positive Tyndall effect, what type of mixture could it not be?a solution27A student dissolves a certain amount of sugar in water at room temperature and reaches the saturation point. What would happen if she heated the water, dissolved more sugar, and then the extra sugar stayed in solution when the solution cooled?She would have created a super-saturated solution.2835.9 grams of NaCl is the maximum amount that will dissolve in 100 mL of water if the water is at a temperature of 20C. If a student dissolves 76 grams of NaCl in 300mL of water at 20oC, what type of mixture has she produced?an unsaturated solution29Which of the solutes solubility is least affected by an increase in the temperature of the solvent?NaCl

30How many grams of potassium iodide will dissolve in 100 g of water if the water is at a temperature of 50oC?about 169 g

31Figure 4 shows properties of four liquids that are insoluble in water. If the four liquids are poured into a beaker containing water, which liquid will form a layer below the water?liquid Q

32What is the best explanation for the fact that gasoline will not dissolve in water?Gasoline is a non-polar solute and water is a polar solvent.33According to Figure 5, about how many grams of KNO3 will dissolve in 100 grams of water at 30C to make a saturated solution?about 42 grams

34Why does saltwater conducts electrical current?Water breaks the salt into charged ions, which conduct current.35If a student dissolves 2.5 moles of NaCl in water and makes 3.5 liters of a saltwater solution, what is the molarity of the solution?M = mol/LM = 2.5 mol / 3.5 L = 0.71 M36If a student dissolves 40.0 grams of KBr in water and makes 1.50 liters of solution, what is the molarity of the solution?M = mol/L40.0 g / 119 g/mol = 0.336 molM = 0.336 mol / 1.5 L = 0.224 M