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53 Cards in this Set
- Front
- Back
the ______ of the water in the _____ was modeled
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salinity profile
San Antonio Bay |
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samples were collected in
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march, a wet month, and april
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the salinity was calculated from an experimentally determined
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chloride ion concentration
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what was the titrant used
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silver nitrate
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what factors are important in determining the biological health of the ecosystem (4)
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temp, pH, salinity, turbidity
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the san antonio bay is fed by
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the guadalupe river
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salinity
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the amount of salt dissolved in a samples of water
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salinity is typically reported in
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grams salt per liter samples or parts per thousand (ppt)
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the most abundant dissolved salt in seawater is
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sodium chloride, NaCl
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equation for ppt NaCl concentration
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g NaCl/g salt water x 1000
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on average the salinity of oceanic waters is
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35 ppt
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river have an average salinity of
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1.6 ppt
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the salinity profiles of bays and estuaries show
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a large variance in salinity according to location, time of day, and time of year
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the weight of NaCl in a saline solution can be calculated if
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the chloride ion concentration in molarity is known [Cl-]
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silver nitrate symbol
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AgNO3
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solubility rules tell us that silver ions (Ag+) will
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form an insoluble solid when reacted with chloride ions (Cl-)
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what is AgCl
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a white silver chloride precipitate
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before the equivalence point there is an excess of
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the chloride ion
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at the equivalence point,
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all the chloride ion has reacted and the precipitate ceases to form
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after the equivalence point,
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the excess silver ion concentration increases
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titrations using silver nitrate can be called 2 things
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argentometric titrations
precipitation titrations |
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argentometric methods have been used in the determination of (6)
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halides, thiocyanate, cyanide, mercaptans, inorganic anions, fatty acids
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the equivalence point of a precipitation titration is defined as being the point at which
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the precipitate no longer forms
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brightly colored adsorbent species or precipitates
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chemical indicators
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Fajan's method relies on the use of
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an adsorbtion indicator, dichlorofluorescein
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dichlorofluorescein is a
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weak organic acid
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adsorption indicators form a _____ as they adsorb to the surface of particles in solution
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colored layer
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the silver chloride particles that form before the equivalence point will adsorb the _____ over the ____
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excess chloride ions
indicator anions |
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what prevents the adsorption of the dichlorofluoresceinate anions (Ind-)?
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the negative charge of Cl- around the AgCl molecule
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once the equivalence point is reached, _____ begin to adsorb on the surface of the precipitate
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Ag+ ions
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dichlorofluoresceinate anions form a ___ layer as they adsorb to the ______
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pink
Ag+ ions |
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what happens to silver cations in bright light
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they are reduced to silver metal
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silver solutions containing a fine gray precipitate, reduced silver,
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should not be used
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what promotes more adsorption of the indicator and results in sharper endpoints
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increasing the precipitate surface areas
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the addition of what to the analyte solution prevents the silver chloride particles from coagulating
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the carbohydrate dextrin
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waste containing silver will
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be collected in waste jars
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what did we do before titrating the bay water samples
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titrated a standard NaCl solution
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when using Fajan's method the endpoint is more clearly seen when
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the indicator is added close to the endpoint
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the solution will change from _____ to _____
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orange/tan
milky pink |
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what is performed to determine the approx endpoint
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a fast titration
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a calculated endpoint volume of less than 1 mL AgNO3 indiciates that
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the sample being titrated is too dilute
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true or false. if you arrive late, you will be able to take the make-up quiz in 412 held
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false
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true or false. if you drop chem 102 you have to drop 112
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false
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formula unit equation?
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NaCl(aq) + AgNO3(aq) <=> AgCl(s) + NaNO3(aq)
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total ionic equation?
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Na+(aq) + Cl-(aq) + Ag+(aq) + NO3-(aq) <=> AgCl(s) + Na+(aq) + NO3-(aq)
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net ionic equation?
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Ag+(aq) + Cl-(aq) <=> AgCl(s)
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we assumed that density of bay water was
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1 g/mL
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real data was collected by ______ in the ______ at tamu
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dr. stephen davis
department of wildlife and fisheries sciences |
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practical salinity is determined by measuring the
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conductivity of water samples
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conductivity of water is directly related to
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salt (electrolyte) concentration
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what connects the gulf of mexico to san antonio bay
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ayers bay
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water flows from ____ to ____ thru ayers bay
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san antonio bay
gulf of mx |
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there is a higher salinity in the bay in
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April
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