Q&A Hero

Q: What is an exothermic reaction? A) It is a reaction that requires heat as a reactant. B) It is a reaction where the products have more energy than the reactants. C) It is a reaction where there is a net adsorption of energy from a reaction. D) all of the above E) none of the above

Q: Many people hear about atmospheric ozone depletion and wonder why we don't simply replace that which has been destroyed. Knowing about CFCs and how catalysts work, explain how this would not be a lasting solution. A) The amount of energy required to create and transport sufficient ozone to the stratosphere would be cost prohibitive. B) Governments would be too slow to respond as they argued about who should shoulder the burden of undertaking such an endeavor. C) Any ozone we placed into the stratosphere would be destroyed by the same catalytic action that destroys naturally occurring stratospheric ozone. D) all of the above

Q: Carefully examine the following reaction sequence for the catalytic formation of ozone, O3, from molecular oxygen, . Which chemical compound is behaving as the catalyst? + 2 NO -> 2 N2 N -> 2 NO + 2 O2 O + 2 -> 2 A) nitrogen monoxide, NOB) nitrogen dioxide, NC) oxygen, D) atomic oxygen, O

Q: A catalytic converter increases the amount of carbon dioxide emitted by an automobile. Is this good news or bad news? A) bad news because carbon dioxide contributes to global warming B) good news because plants thrive on carbon dioxide C) bad news because the carbon dioxide contributes to acid rain D) good news because it means more noxious chemicals are not being emitted

Q: The portion of the atmosphere that filters out 95 percent of the incident UV radiation is the A) ozone layer. B) stratosphere. C) troposphere. D) aerosol layer. E) particulates.

Q: Why is there a drastic reduction in ozone in the spring? A) There is a sudden increase in Cl atoms in the spring. B) It is warmer in the spring. C) There are more chlorofluorocarbons in the spring. D) all of the above E) only a and b

Q: How is ozone produced in the upper atmosphere? A) It forms by reaction of oxygen molecules with UV light. B) It forms by nuclear decomposition of oxygen. C) It diffuses from the lower atmosphere. D) It forms by the reaction of nitric dioxide and oxygen. E) all of the above

Q: Since some of the compounds that are destroying ozone are found in nature normally, how is it possible to tell that the reactive molecules destroying the ozone are due to our actions? A) They are accompanied by compounds that are only man-made. B) The compounds only increased in the past few years. C) The isotope distribution is unique to man-made elements. D) The chemical composition is different than natural compounds. E) all of the above

Q: The chlorinated fluorocarbons molecules are acting as a(n) ________ by converting hundreds of thousands of molecules before they are inactivated. A) catalyst B) aerosol C) active site D) acid E) base

Q: What is the main difficulty in trying to eliminate chlorinated fluorocarbons from the atmosphere? A) They are very stable and take a long time to decompose completely. B) They are too light and blow away. C) They do not absorb ultraviolet radiation. D) all of the above E) only a and b

Q: What is the environmentally unfriendly component of chlorinated fluorocarbons that ultimately damages ozone? A) chlorine atoms B) fluorine atoms C) carbon atoms D) molecular fragments of carbon and fluorine E) all of the above

Q: Why do the natural reactions involving ozone not lead to depletion of the ozone layer? A) Ozone continually rises from the troposphere. B) Ozone is too diffuse. C) Ozone breaks into fragments that can reassemble into more ozone. D) UV radiation generates more ozone. E) c and d

Q: Which of the following statements accurately describes the action of ozone? A) It absorbs UV radiation and undergoes fragmentation. B) It reflects UV radiation back into space. C) It reflects heat back into space. D) It emits UV radiation when excited by sunlight. E) none of the above

Q: Which of the following statements about ozone is true? A) Ozone in the stratosphere is beneficial. B) Ozone in the troposphere is a pollutant. C) Ozone is generated from photochemical reactions of hydrocarbons. D) none of the above E) both a and b

Q: The ________ is what needs to be overcome in a reaction so that it can proceed to the products. A) activation energy B) catalyst C) entropy D) thermodynamics E) bond energy

Q: Some reactions are more sluggish than others. To speed up these reactions and save energy a(n) ________ is sometimes added. A) catalyst B) activator C) heat source D) exotherm E) reaction profile

Q: Which of the following statements about catalysts is NOT true? A) A catalyst alters the rate of a chemical reaction. B) A catalyst can be consumed in a reaction as long as it is regenerated. C) A catalyst can be used to speed up slow reactions. D) A catalyst does not change the energy of the reactants or the products. E) All of the above are true.

Q: If the following graphs are for the same reaction, which one is most likely the one with an added catalyst? A) a B) b C) c D) d E) All have had catalyst added.

Q: How does a catalyst increase the rate of a reaction? A) It lowers the activation energy. B) It is neither created nor consumed in a reaction. C) It has nothing to do with the rate of reaction. D) It increases the energy difference between the reactants and products. E) It raises the activation energy of the reactants, which makes the reaction proceed faster.

Q: Is the synthesis of ozone, , from oxygen, , an example of an exothermic or endothermic reaction? A) exothermic because ultraviolet light is emitted during its formation B) endothermic because ultraviolet light is emitted during its formation C) exothermic because ultraviolet light is absorbed during its formation D) endothermic because ultraviolet light is absorbed during its formation

Q: What can you deduce about the activation energy of a reaction that takes billions of years to go to completion? How about a reaction that takes only fractions of a second? A) The activation energy of both these reactions must be very low. B) The activation energy of both these reactions must be very high. C) The slow reaction must have a high activation energy while the fast reaction must have a low activation energy. D) The slow reaction must have a low activation energy while the fast reaction must have a high activation energy.

Q: An Alka-Seltzer antacid tablet bubbles vigorously when placed in water but only slowly when placed in an alcoholic beverage of the same temperature containing a 50:50 mix of alcohol and water. Propose a probable explanation involving the relationship between the speed of a reaction and molecular collisions. A) The alcohol absorbs the carbon dioxide bubbles before they escape the liquid phase. B) Alcohol molecules are more massive than water molecules, hence they move slower and their collisions are not as forceful. C) The tablet reacts with water but not the alcohol. D) In a 50:50 mix there are fewer water molecules for the antacid molecules to collide with.

Q: Why is heat often added to chemical reactions performed in the laboratory? A) to allow a greater number of reactants to pass over the activation energy B) to increase the rate at which reactant collide C) to compensate for the natural tendency of energy to disperse D) all of the above

Q: Why does a glowing splint of wood burn only slowly in air, but rapidly in a burst of flames when placed in pure oxygen? A) There is a greater number of collisions between the wood and oxygen molecules. B) Oxygen is a flammable gas. C) Pure oxygen is able to absorb carbon dioxide at a faster rate. D) A glowing wood splint is actually extinguished within pure oxygen because there's no room for the smoke to expand.

Q: The yeast in bread dough feeds on sugar to produce carbon dioxide. Why does the dough rise faster in a warmer area? A) There is a greater number of effective collisions among reacting molecules. B) Atmospheric pressure decreases with increasing temperature. C) The yeast tends to "wake up" with warmer temperatures, which is why baker's yeast is best stored in the refrigerator. D) The rate of evaporation increases with increasing temperature.

Q: A refrigerator delays the spoilage of food by A) killing microorganisms. B) slowing down the rate of chemical reactions within microorganisms. C) expanding the water found within microorganisms. D) diminishing the supply of oxygen to microorganisms.

Q: R = reactants P = products For the above energy profiles, which reaction has the lowest activation energy? A) a B) b C) c D) d E) All have the same activation energy.

Q: R = reactants P = products For the above energy profiles, which reaction has the highest activation energy? A) a B) b C) c D) d E) All have the same activation energy.

Q: What is the activation energy? A) the minimum amount of energy to break the bonds in reactants B) the amount of energy required to activate a phase change C) the energy difference between the reactants and the products D) the amount of energy required to separate reactants from the products E) the hill

Q: Why might increasing the temperature alter the rate of a chemical reaction? A) The molecules will have a higher kinetic energy and bump into one another harder. B) The molecules are less reactive at higher temperatures. C) The molecules will more likely combine with other atoms at high temperature to save space. D) The density decreases as a function of temperature and this leads to an increase in volume which drops the rate of reaction. E) none of the above

Q: Why might increasing the concentration of a set of reactants increase the rate of reaction? A) You have increased the chances that any two reactant molecules will collide and react. B) You have increased the ratio of reactants to products. C) The concentration of reactants is unrelated to the rate of reaction. D) The rate of reaction depends only on the mass of the atoms and therefore increases as you increase the mass of the reactants. E) none of the above

Q: What is a reaction rate? A) It is the speed at which reactants are consumed or product is formed. B) It is the balanced chemical formula that relates the number of product molecules to reactant molecules. C) It is the ratio of the masses of products and reactants. D) It is the ratio of the molecular masses of the elements in a given compound. E) none of the above

Q: How many moles of water, O, are produced from the reaction of 16 grams methane, C, with an unlimited supply of oxygen, . How many grams of O is this?C + 2 -> C + 2 OA) 0.889 mole, which is 16 gramsB) 2.0 moles of water, which is 32 gramsC) 2.0 moles of water, which is 36 gramsD) 1.0 mole of water, which is 18 grams

Q: How many grams of water, O, and propene, , can be formed from the reaction of 6.0 g of 2-propanol, O?O -> + O2-Propanol Propene WaterA) 6.0 grams of propene, 0.0 grams of waterB) 1.8 grams of propene, 4.2 grams of waterC) 0.0 grams of propene, 6.0 grams of waterD) 4.2 grams of propene, 1.8 grams of water

Q: Small samples of oxygen gas needed in the laboratory can be generated by any number of simple chemical reactions, such as2 KCl (s) -> 2 KCl (s) + 3 (g)What mass of oxygen (in grams) is produced when 122.6 g of KCl (formula mass = 122.6 amu) takes part in this reaction?A) 32.00 gramsB) 48.00 gramsC) 96.00 gramsD) More information is needed.

Q: How many molecules of aspirin (formula mass aspirin = 180.0 amu) are there in a 0.250-gram sample? A) 6.02 B) 8.36 C) 1.51 D) More information is needed.

Q: A 1.00 carat pure diamond has a mass of 0.20 grams. How many carbon atoms are there within this diamond? A) 6.0 carbon atoms B) 2.0 carbon atoms C) 1.0 carbon atoms D) 6.0 carbon atoms

Q: Why are there few odors emanating from a properly managed composting toilet? A) Tight seals prevent the escape of odors. B) Odors are absorbed by a layer of water. C) Decomposition is aerobic. D) The ventilation system steers odors through a carbon filter.

Q: Where does most of the solid mass of raw sewage end up after being collected at a treatment facility? A) It is injected into the water table. B) It is buried in landfills. C) It is sold to farmers for fertilizer. D) It is tapped for the generation of methane gas.

Q: Why is flushing a toilet with clean water from a municipal supply about as wasteful as flushing it with bottled water? A) Bottled water is typically made from municipal water. B) Municipal water and bottle water have about the same level of purity. C) Both the bottled water and municipal water are generally free of pathogens. D) all of the above

Q: What is an advantage of using chlorine gas to disinfect drinking water supplies? A) It provides residual protection against pathogens. B) It gives the water a fresh taste. C) Residual chlorine in water helps to whiten teeth. D) Excess chlorine is absorbed in our bodies as a mineral supplement.

Q: How is most of the energy required for secondary wastewater treatment consumed? A) as electricity to power air pumps for aeration B) as electricity to illuminate UV lamps C) as heat to run distillation equipment D) as electricity to power hydraulic pumps for reverse osmosis E) none of the above

Q: What is the easiest way to eliminate organic components? A) Aerate the solution and let bacteria consume the organics. B) Treat the solution with UV radiation. C) Filter the solution through activated carbon filters. D) Use reverse osmosis. E) all of the above

Q: Why is secondary treatment often needed for sewage? A) The dissolved organics are too high and lead to bacterial growth. B) The solution is contaminated with dangerous bacteria. C) There are too many dissolved inorganic compounds. D) There are too many finely divided particles that need to be filtered. E) none of the above

Q: What is the first step in treating raw sewage? A) filtration of solids B) removal of fine particles by settling C) removal of grit by settling D) removal of sludge E) disinfection

Q: Which of the following statements about sewage is not true? A) All municipalities must treat sewage the same way. B) All municipalities must treat sewage. C) Once treated, sewage is released to the environment. D) Treated sewage becomes drinking water downstream. E) None of the above are true.

Q: Does the concentration of chlorine in drinking water tend to increase or decrease as it leaves the water treatment plant and disperses into the community? Why? A) Increases. As the chlorine reacts with the bacteria in the water, more chlorine is produced. B) Increases. As the water evaporates the chlorine concentration would increase in the remaining water. C) Decreases. Evaporative processes and reaction with organic bacteria would decrease the chlorine concentration. D) Neither. The chlorine concentration in the water does not vary as the water is dispersed into the community.

Q: How does the purchase and use of a home beverage carbonator help to minimize carbon dioxide emissions? A) It allows the consumer to avoid using commercial sodas that require much gasoline for shipping. B) Home carbonators are more efficient at forcing the carbon dioxide into solution. C) Industrial carbonators are driven by mechanical pumps that require large amounts of gasoline in order to operate. D) False. Home carbonators have the net effect of producing more carbon dioxide per liter of carbonate water.

Q: Some people fear drinking distilled water because they have heard it leaches minerals from the body. What scientifically sound information might be offered to such a person? A) add small amounts of salt to the distilled water before drinking it B) chill the distilled water to decrease its leaching potential C) buy distilled water that has also undergone reverse osmosis D) Distilled water is relatively pure water, which loses its purity once it mixes with everything else in your stomach.

Q: Why do red blood cells, which contain an aqueous solution of dissolved ions and minerals, burst when placed in fresh water? A) The dissolved ions provide a pressure that eventually bursts open the cell. B) More water molecules enter the cell than leave the cell. C) The fresh water acts to dissolve the blood cell wall. D) all of the above

Q: Why is it significantly less costly to purify fresh water through reverse osmosis than to purify salt water through reverse osmosis? A) The osmotic pressure exerted by fresh water is less. B) The osmotic pressure exerted by fresh water is greater. C) For non-coastal regions, the salt water needs to be transported many miles from the oceans. D) The expense of reverse osmosis is not dependent upon the salt concentration in the water.

Q: Cells at the top of a tree have a higher concentration of sugars than cells at the bottom. How might this fact assist a tree in moving water upward from its roots? A) Cells with high concentrations of sugar are more dense. As these cells migrate downwards, cells containing fresh water are able to migrate upwards. B) Water is pushed upwards by osmostic pressure. C) It doesn't. In fact, water makes it to the top of a tree because that is where the water molecules are being evaporated. D) Fresh water is drawn upwards to the sugar containing cells by way of dipole-dipole molecular interactions.

Q: Might reverse osmosis be used to obtain fresh water from a sugar-water solution? A) No, osmosis and reverse osmosis only apply to aqueous solutions containing ions. B) Yes, reverse osmosis can be applied to any aqueous solution for the generation of fresh water. C) No, the molecular attractions between sugar and water are too strong. D) Yes, because sugar molecules are smaller than sodium or chloride ions.

Q: Why is it important to conserve fresh water? A) There is little fresh water available to us on our planet. B) As the human population grows, so does our need for fresh water. C) It is expensive to purify nonpotable water. D) all of the above

Q: Red blood cells have a high concentration of dissolved ions. When placed into pure water they rupture. Why? A) Osmosis draws water into the cell until it pops. B) Water dissolves the cell membrane. C) Osmosis draws water out of the cell until it tears. D) The cells are not stable outside of a biological host. E) none of the above

Q: Which of the following would cost the least to purify by reverse osmosis? A) agricultural runoff B) sea water C) brackish water D) All of the above are the same. E) None of the above can be purified by reverse osmosis.

Q: Which of the following describes reverse osmosis? A) High pressure saltwater is forced against a semipermeable membrane and fresh water comes out. B) Saltwater is chemically reacted with aluminum particles, which chemically binds to the chloride ions. C) The water is heated until it evaporates and condenses in a pure form. D) High pressure saltwater is reacted with aluminum, which absorbs the sodium ions in an oxidation reaction. E) none of the above

Q: Which of the following statements about desalinization is untrue? A) You can use osmosis to remove salt from saltwater. B) You can use distillation to separate salt from saltwater. C) Desalinization is an energy intensive process. D) All are untrue. E) Only a and b are untrue.

Q: What happens if you were to place a dilute solution that is in a bag made of a semipermeable membrane and were to then suspend it in a very concentrated solution? A) The size of the suspended bag would decrease. B) The size of the suspended bag would increase. C) The size of the bag would not change. D) The solutions would eventually reach the same concentration. E) only c and d

Q: What happens if you were to place a concentrated solution into a bag made of a semipermeable membrane and were to then suspend it in a very dilute solution? A) The size of the suspended bag would decrease. B) The size of the suspended bag would increase. C) The size of the bag would not change. D) The solutions would eventually reach the same concentration. E) only c and d

Q: During osmosis A) the water moves into the concentrated solution faster than it leaves. B) the ions move into the concentrated solution faster than they leave. C) the water moves more slowly into the concentrated solution than it leaves. D) the ions move into the concentrated solution slower than they leave. E) all of the above

Q: Which of the following accurately describes osmosis? A) The more concentrated solution absorbs water from the less concentrated solution. B) The less concentrated solution absorbs water from the more concentrated solution. C) The less concentrated solution gets more dilute. D) The ions migrate from the more concentrated solution to the less concentrated. E) none of the above

Q: What makes a semipermeable membrane selective for one chemical species but not another? A) The pores in the membrane select by size, they are big enough for water only. B) The material is hydrophilic and therefore only allows water through. C) The material is hydrophobic and therefore only allows water through. D) The material chemically reacts with everything but water. E) none of the above

Q: What is the special property of a semipermeable membrane that makes osmosis possible? A) The pores in the membrane only allow water to pass through. B) Water only moves through the membrane in one direction. C) Only the ions travel through the membrane. D) Ions only move one way through the membrane. E) none of the above

Q: Why aren't solar stills used in more large urban areas? A) They take up too much space. B) They do not produce enough water. C) They require too much sunlight. D) They are not as efficient are reverse osmosis. E) all of the above

Q: Why isn't distillation used commercially to purify water? A) Water requires large amounts of energy to boil affordably. B) Bacteria are not killed during the distillation process. C) Odd smelling contaminants boil at lower temperatures than water and so are impossible to remove. D) Distillation does not remove suspended particles such as dirt and humus. E) none of the above

Q: Passing arsenic contaminated water through a long pipe filled with sand and iron powder leads to removal of the arsenic by A) a physical change. B) an oxidation-reduction reaction. C) ion exchange. D) filtering out the suspended arsenic particles. E) only a and b

Q: Treating water with chlorine or ozone during water purification is an example of A) a physical change. B) a chemical reaction. C) ion exchange. D) a solid dissolving in a liquid. E) only a and b

Q: What is the purpose of treating water with chlorine gas or ozone during water purification? A) to kill bacteria B) to improve taste C) to improve color D) to remove solids E) none of the above

Q: What is the purpose of allowing water to cascade or bubble in a fountain during the purification process? A) to mix air into the water and improve flavor B) to remove radioactive gases C) to remove unpleasant smelling chemicals like sulfur D) all of the above E) only A and B

Q: Allowing water to cascade or bubble in a fountain during the purification process is an example of A) a gas dissolving in a liquid. B) a chemical reaction. C) ion exchange. D) a solid dissolving in a liquid. E) only a and b

Q: What is the purpose of adding aluminum salts and a base to water during water treatment? A) The two together gel and trap dirt and bacteria. B) The higher pH kills bacteria. C) The aluminum removes the rust taste from the water. D) The base dissolves the dirt. E) It improves the taste.

Q: Water being purified using aluminum salts and a base is an example of A) a physical separation. B) a chemical reaction. C) an acid-base reaction. D) a chemical separation. E) none of the above

Q: Which of the following is not a typical use for potable water? A) irrigation B) cooking in a pot C) flushing a toilet D) drinking E) boiling

Q: Fatty acid molecules can also align to form a bilipid layer that extends in 3-dimensions. Shown below is a cross section of this structure. What is this structure called? (Hint: it forms the basis of all life.) A) DNA B) a nucleoside C) a cell D) a gene

Q: Why do hot water heaters lose their efficiency quicker in households with hard water? A) The hard water calcium and magnesium ions corrode the heating element. B) The hard water calcium carbonate deposits oxidize the inner tank wall. C) The calcium carbonate on the inner surface of the hot water tank builds up to the point that it insulates the water from the heating element. D) The hard water calcium ions exchange with iron ions from the inner metal wall which react with the water heater base to form rust and deteriorate the bottom of the tank.

Q: Why might softened water not be good for some one who is trying to reduce their dietary sodium ion intake? A) The potassium used in the softener to replace the calcium and magnesium ions increases the sodium retention in the body. B) Water softeners work by replacing the calcium and magnesium ions of the water with sodium ions; softened water contains increased levels of sodium ions. C) The softened water leaches sodium from the body, so a person might not be getting the dietary recommended levels of sodium. D) A person needs a certain level of calcium and magnesium in the water to help excrete the sodium from their body.

Q: Which of the following statements best describes what is happening in a water softening unit? A) Thehard ions in water are exchanged for ions that do not interact as strongly with soaps. B) The hard ions are all trapped in the softener, which filets out all the ions. C) The ions in the water softener are softened by chemically bonding with sodium. D) The sodium is removed from the water, making the water interact less with the soap molecules. E) none of the above

Q: Why might sodium carbonate (washing soda, Na2CO3) be added to hard water to aid in cleaning? A) The hard ions in the water are more attracted to the carbonate ions -2 charge. B) Thehard ions are dissolved by the added sodium ions. C) The soap gets softer due to the added ions. D) The ions solubilize the soap due to ion-ion intermolecular attraction, which improves the cleaning ability. E) none of the above

Q: Which of the following might best describe the product obtained from soap and hard water (i.e., soap scum)? A) a B) b C) c D) d E) none of the above