chem – Flashcards
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define specific heat
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the heat required to raise the temperature of the unit mass of a given substance by a given amount (usually one degree).
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what are some path functions
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heat, work, distance traveled
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what are some state functions
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energy, enthalpy
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what info is obtained with a calorimeter
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the change in heat associated with a chemical reaction or process
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if temp A is less than the initial temp of B, what is the direction of the heat flow
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From B to A, and the final temp is equal to eachother because heat flows until both objects reach the same temperature
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The temperature of a sample of silver increased by 22.9 °C when 275 J of heat was applied. What is the mass of the sample? specific heat of silver is 0.235
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0.235 x 22.9 =5.38
275/5.38 = 51.10
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A student uses a pipet designated for the NaOH solution to pipet the H2SO4 solution
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contaminates
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Several students have left over reagents after the completion of an experiment and decide to return the excess to the proper container.
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contaminates
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here is only one spatula available to measure out several different white powders.
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contaminates
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Rather than wasting multiple weigh boats, a student decides to wash and dry a single weigh boat in between uses.
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does not contaminate
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A group of students must use the same 500 mL volumetric flask to make solutions. In between each use they wash and dry the flask.
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does not contaminate
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At the end of the day, the waste bottle is so full that a student decides to dump his waste into an almost empty bottle of stock KI solution.
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contaminates
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What is the buret rinsed with and why?
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The solution that is being titrated to ensure that when added to the buret, it will not be diluted with excess water.
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During the titration (fajans titration)
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Ag+ is added to Cl-
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At the endpoint, just passed the equivalence point
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An excess of Ag ions imparts a positive charge to the surface of the precipitate.
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Detection of the endpoint by a dye color change:
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An anionic dye binds to the positive surface of the precipitate.
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Define enpoint of titration
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It is when a change that indicates equivalence is observed in the analyte solution.
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What effect does increasing the concentration of a dissolved solute have on each of the following colligative properties?
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elevation: boiling point
depression: freezing point, vapor pressure
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most molecular solutes, table sugar, methanol, CH3OH, a substance that forms an aqueous solution that does not conduct electricity,
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non electrolyte
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sodium chloride, NaCl, potassium iodine, KI, sodium hydroxide, NaOH, a soluble ionic compound
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electrolyte
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where Kf is the freezing point depression constant and m is the molality of the solution. Which of the following states the correct reasoning for the use of molality (rather than molarity) in this equation?
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As the temperature of a solution changes, its volume will also change, which will affect its molarity but not its molality.
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molality
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mol/kg
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The volume of solvent traveling through the column per unit time.
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volumetric flow rate
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The elapsed time between sample injection and detection.
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retention time
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The time required by a retained solute to travel through the column beyond the time required by the unretained solvent.
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retention factor
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The distance traveled by the solvent per unit time.
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linear flow rate
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Describes the amount of time that a sample spends in the stationary phase relative to the mobile phase. It is sometimes also called the capacity factor or capacity ratio.
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adjusted retention time
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Volume of the mobile phase required to elute a solute from the column.
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retention volume
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Ratio of the adjusted retention times or retention factors of two solutes. It is sometimes also called the separation factor.
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relative retention
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The ratio of the solute concentrations in the mobile and stationary phases.
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partition coefficient
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Major underlying principle of chromatography
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Separation will be achieved if one component adheres to the stationary phase more than the other component does.
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How can you experimentally determine the pKa of acetic acid?
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Determine the pH of the solution half way to the end-point on the pH titration curve for acetic acid.
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How should the solute and solvent be mixed in the container?
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Mix a small amount of water with the solute to dissolve it, then fill with water to the 250-mL mark.
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If a compound is blue in color...
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It absorbs orange light
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During a spectrophotometric analysis of an unknown, you measure your unknown solution's absorbance, and the value is higher than the highest standard you used to make your standard curve. What should you do to make sure you can use your standard curve to determine the unknown's concentration?
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Dilute the unknown so that it will have an absorbance within the standard curve. Once the diluted unknown concentration is determined, the full strength concentration can be calculated if the dilution process is recorded. Beer's Law only applies to dilute solutions, so diluting the unknown is better than making new standards.
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Which type of research is carried out in an effort to provide results suitable for practical use?
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applied
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Which of the following agencies provide research funding that is not federally financed?
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american diabetes association
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Ferric chloride, potassium fluoride, and ferrous salts are used to prepare the magnetic clay.
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false
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PAHs interact with bentonite clay by intercalation.
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true
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Bentonite clay sequesters PAHs by the formation of permanent covalent bonds.
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true
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A voltmeter is primarily used to measure
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electrical potential
