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Topic: Equivalence Point

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	Equivalence Point
		The equivalence point in a titration is the point at which a stoichiometric amount of the standard solution has been mixed with your analyte.
		Experimentally, the equivalence point of a pH titration corresponds with the inflection point on the titration curve (pH vs.
		The inflection point is difficult to accurately measure from the titration curve.
	www.chem.vt.edu /chem-dept/anderson/2124/equivalence-point.html (119 words)

	PlanetMath: homotopy equivalence
		This homotopy equivalence is sometimes called strong homotopy equivalence to distinguish it from weak homotopy equivalence.
		For topological spaces, homotopy equivalence is an equivalence relation.
		This is version 10 of homotopy equivalence, born on 2002-01-23, modified 2003-07-10.
	planetmath.org /encyclopedia/HomotopyEquivalence.html (102 words)

	[No title]
		The dichromate volume needed to reach the equivalence point was taken as the average of the two ends and was calculated to be 23.75ml.
		Equivalence point The equivalence point potential was determined from the titration curve as the voltage corresponding to the halfway point of the steepest slope.
		At the equivalence point, there is less Fe+2 for the dichromate to react with, and instead, the dichromate reacts with the electrode leaving higher error to the model.
	www.seas.upenn.edu /courses/belab/LabProjects/1997/BE309F97T4R01.doc (6321 words)

	Acid Base Titration-Comp.1-WWW (Site not responding. Last check: 2007-10-23)
		This point in the titration is known as the equivalence point.
		The equivalence point of the titration is found by drawing a vertical line through the midpoint of the steep portion of the curve and then dividing that portion of the curve into two equal parts.
		Determine the equivalence point and volume at the equivalence point as you did in Part I. Calculate what the pH should be at the equivalence point and compare it to the value that you measured.
	www.pitt.edu /~n3lsk/0114/titrcurveproc.html (1995 words)

	CHP - Acid-Base Titration
		At the equivalence point the pH, 7, is determined by the dissociation of water.
		After the equivalence point, the situation is the same as for a strong acid and the pH is determined by the concentration of excess strong base.
		The end point might differ slightly from the equivalence point, and the difference between the equivalence point and the end point is called the titration error.
	www.chem.vt.edu /chem-ed/titration/acid-base-titration.html (704 words)

	Determination of the Carbonate Content of a Soda-Ash Sample
		The equivalence point for reaction (2) occurs at a pH of roughly 4.0.
		Since the equivalence point is at pH 8.4 an amount of acid somewhat in excess of one equivalent is used, and the titration gives only a rough measure of the carbonate content of the original solution.
		The first equivalence point of CO is reached when the solution has changed from pink almost to colorless but still has a ghostly hint of pink left in it.
	chemistry.csudh.edu /oliver/che230/labmanual/carbnate.htm (2258 words)

	Chapter 17, Section 3 (Site not responding. Last check: 2007-10-23)
		Before the equivalence point is reached, the neutralization reaction results in a solution containing a mixture of the weak acid and its salt.
		The calculation of this pH is the same as that for points after the equivalence point in the titration of a strong acid with a strong base.
		It is important to note that the pH at the equivalence point in the titration of the weak acid is considerably higher than it is in the titration of the strong acid.
	cwx.prenhall.com /bookbind/pubbooks/blb/chapter17/medialib/blb1703.html (2803 words)

	Chapter 4. Titrimetry
		The equivalence point is the point at which a volume, a mass or a quantity of charge equivalent to the amount of analyte present in the sample to be measured is reached.
		The equivalence point for this reaction occurs at pH 7-8.
		As the equivalence point is approached in an acid-base titration the concentration of the species in excess continues to decrease.
	www.csudh.edu /oliver/che230/textbook/Vol04.htm (2642 words)

	Titrations and Buffers (Site not responding. Last check: 2007-10-23)
		At the equivalence point, the concentration of the hydronium ions from the acid is so small that the autoionization of water must be considered when calculating pH.
		Since all of the hydrofluoric acid has reacted at the equivalence point, the number of moles of fluoride ions is the same as the initial number of moles of hydrofluoric acid.
		The total volume at the equivalence point is 60.0 mL, yielding a molarity of 4.0 mmol/60.0 mL=.07 M for the fluoride ions.
	www.scientia.org /cadonline/Chemistry/acidbase/titration.ASP (1789 words)

	SparkNotes: Titrations: Acid-Base Titrations
		Also remember that the equivalence point for a strong acid-strong base titration curve is exactly 7 because the salt produced does not undergo any hydrolysis reactions.
		Note that the pH of a solution at the equivalence point has nothing to do with the volume of titrant necessary to reach the equivalence point; it is a property inherent to the composition of the solution.
		The pH at the equivalence point is calculated in the same manner used to calculate the pH of weak base solutions in Calculating pH's.
	www.sparknotes.com /chemistry/acidsbases/titrations/section1.html (711 words)

	CH232- Lab Experiment #2 - Potentiometric Titration of a Weak Acid
		of the acid and the equivalence point are determined.
		Based on the equivalence point, the concentration of the unknown acid is determined.
		Using this volume, determine the number of equivalents of present in the unknown sample and the equivalent weight of the unknown sample.
	chemistry.lssu.edu /CH332/lab2.htm (755 words)

	Section 6.6.4
		The points on the titration curve that are somewhat removed from the carbonate and bicarbonate equivalence points are used by the Gran method (Pankow, 1991).
		A sufficient number of titration points beyond the bicarbonate equivalence point are needed to ensure the accuracy of the calculation.
		Beyond the bicarbonate equivalence point, the shape of the curve is determined by hydrogen ions in excess of all hydrogen ion acceptors in the sample.
	water.usgs.gov /owq/FieldManual/Chapter6/section6.6/html/section6.6.4.htm (5665 words)

	Triprotic Acid Titration Examples
		Phosphoric acid is a good example of a titration where the first two equivalence points, corresponding to base reaction with the first and second protons, respectively, are clearly visible.
		In this case we might expect that the first two equivalence point would be obscured by the fact that the two acidic pKa are relatively close.
		One thing to notice is that the first equivalence point is "lost" and a large change in pH only occurs at the second equivalence point.
	dwb.unl.edu /Teacher/NSF/C12/C12Links/www.chem.usu.edu/faculty/sbialkow/Classes/360/Overheads/H3A/H3A.html (1011 words)

	ChemLab - Chemistry 3/5 - Monoprotic and Polyprotic Acids - Chemistry
		When the equivalence point is reached, the pH of the solution will change rapidly, because all the acid has reacted with the added base.
		The equivalence point, when enough base is added to react with all the acid present, exhibits the sharp increase in pH, as discussed above.
		at a point midway between equivalence points, at the center of the buffer region.
	www.dartmouth.edu /~chemlab/chem3-5/acid1/full_text/chemistry.html (2770 words)

	unit02-sect03-les01-lessona (Site not responding. Last check: 2007-10-23)
		Recall that the equivalence point of a titration occurs when the amount of titrant added is just enough to neutralize the sample - neither the titrant nor the sample is in excess.
		The equivalence point is below pH 7 (actually about pH 5.3) because the weak acid formed as ammonia is neutralized has the ability to donate a proton to water thereby reducing the pH of the mixture.
		After the equivalence point is reached, further addition of HCl produces the same decline seen in the titration of a strong base.
	www.cdli.ca /courses/chem3202/unit02/section03/lesson04/3-lesson-a.htm (1240 words)

	pH curves (titration curves)
		That means that at the equivalence point (where you had mixed the solutions in the correct proportions according to the equation), the solution wouldn't actually be neutral.
		The term "equivalence point" means that the solutions have been mixed in exactly the right proportions according to the equation.
		However, this is a very minor point in the present context, and you would probably do better to read the whole of the current page before you follow this up.
	www.chemguide.co.uk /physical/acidbaseeqia/phcurves.html (1628 words)

	Titration of a Diprotic Acid:
		Therefore, the volume of NaOH added at the second equivalence point is exactly twice that of the first equivalence point (see Equations 3 and 5).
		The first half-titration point volume can be found by dividing the first equivalence point volume by two.
		The second half-titration volume (Point 2 in Figure 3) is midway between the first and second equivalence point volumes (1st EP and 2nd EP).
	www.sas.upenn.edu /~tloschia/AP/labs/diprotic.htm (1409 words)

	1.5 pH at the equivalence point (Site not responding. Last check: 2007-10-23)
		The equivalence point is defined as the point (in a titration or neutralization) at which the moles of OH- that can be supplied by the base is equal to the moles of H3O+ that can be supplied by the acid.
		For monoprotic acids and bases, this is the point at which the moles of acid equal the moles of base.
		Adding an equivalent of acid to a base means adding the same number of (potential) moles of H3O+ as one has (potential) moles of OH-.
	www.chemistry.mcmaster.ca /~austen/1aa3/notes/day4/sld006.htm (171 words)

	[No title]
		The degree of dissociation of the weak acid is used to characterize the acid, and is calculated according to the equation: EMBED Equation.3 where Ka is the dissociation constant.
		This condition is met halfway to the equivalence point of the titration.
		Data Analysis: The equivalence point for your titration is defined as the point of inflection (where the slope changes) on the titration curve.
	www.apsu.edu /brennanc/Chem3211/Chem3211_06_Lab04.doc (1163 words)

	Acid-Base Indicators (Site not responding. Last check: 2007-10-23)
		They are used in these reactions to determine the equivalence point and the end point.
		Once the equivalence point has been reached, the amount of sample that was present in the solution can be calculated.
		This is close to the equivalence point of 7.
	basc.chem-eng.utoronto.ca /~sutarwa/che200.htm (1934 words)

	[No title]
		Since the other two equivalence points fall outside of this range, propyl red would not be a good indicator.
		The color change would occur after the equivlance point in the case of 3.5 and too soon for the reaction who’s equivalence point is at 6.9.
		Vol of titrant at the equivalence point titrant analyte 2.
	frcc.cc.co.us /docs/cms/Titrations.doc (1532 words)

	[No title] (Site not responding. Last check: 2007-10-23)
		At the equivalence point, we have a salt of a weak acid.
		In the second buffer region, we have a mixture of bicarbonate and carbonic acid, and at the second equivalence point we have carbonic acid.
		The species present and the equations used for calculating pH at the beginning, the equivalence points, the buffer regions, and beyond the last equivalence point are shown.
	emp.byui.edu /ZAUGGN/Chem220/Chapternotes/Christian6thed/220CH8NOTES.HTM (1270 words)

	[No title]
		Slide 6 EMBED PowerPoint.Slide.8 The equivalence point is defined as the point (in a titration or neutralization) at which the moles of OH- that can be supplied by the base is equal to the moles of H3O+ that can be supplied by the acid.
		This is different from the equivalence point of a strong acid with a strong base.
		Also from Chang, the addition of weak acid to strong base (same reactants) pH at the equivalence point is unchanged by the direction of approach Figure 18.7 Addition of a strong base to a weak diprotic acid.
	www.chemistry.mcmaster.ca /~austen/1aa3/notes/day4/day4.doc (1629 words)

	Chemistry : Chapter 16 : Titrations (Site not responding. Last check: 2007-10-23)
		The equivalence point is the volume when the reactants are in exact stoichiometric ratio.
		This means that you can use stoichiometry, as described in Chapters 4 and 5, to determine the equivalence point.
		Since it changes color at the equivalence point (it doesn't have to hit exactly), this would be a reasonable choice.
	www.wwnorton.com /chemistry/concepts/chapter16/ch16_7.htm (1502 words)

	In-Class Section
		The equivalence point is the condition in a titration where the amount of analyte equals, reactivity wise, the amount of titrant added.
		Determining this point is the point of the titration.
		Draw the second derivative curve for the equivalence point of a strong acid-strong base titration.
	www.cbu.edu /~mcondren/c214e202.htm (621 words)

	Titrations
		The equivalence point is the point at which a stoichiometrically equivalent amount of base has been added to the acid.
		The point in the titration at which the colour changes is known as the endpoint of the titration.
		The equivalence point is a single point defined by the reaction stoichiometry as the point at which the base (or acid) added exactly neutralizes the acid (or base) being titrated.
	www.chemistry.nmsu.edu /studntres/chem116/notes/titrations.html (1498 words)

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