A titration in which a weak base is titrated with a strong acid will look very similar to the previous titration curve, except backwards. As we add more NaOH(aq) past the equivalence point for the neutralisation reaction, the moles of OH-(aq) in this added volume of solution are all in excess, so the pH of the solution increases, but as we keep adding more and more NaOH(aq) the line levels off as it approaches the pH of the NaOH(aq) being added (for 0.200 mol L-1 NaOH(aq) pH = 13.3). This particular resource used the following sources: http://www.boundless.com/ The curve’s turning point is the equivalence point, right where the amount of hydroxide added matches the amount of acetic acid originally present. Titration curves for weak acid v strong base:- 20. The simplest acid-base reactions are those of a strong acid with a strong base. When the NaOH is in excess, the pH change is the same as in any system dominated by NaOH. A titration in which a weak acid is titrated with a strong base will look like this: Titration curve for weak acid with strong base A slide modeled from this curve would be a more mellow ride. Because you have got a weak base, the beginning of the curve is obviously going to be different. If pH = 6.0 at the halfway point to equivalence, what is the K b … MES is an abbreviation for 2-(N-morpholino)ethanesulfonic acid, which is a weak acid with pKa = 6.27. titration, (3) evaluate a pH titration curve and determine the pH of a weak acid / strong base titration at the equivalence point, (4) use the molar solubility, as determined from the hydrogen ion concentration, to determine the K sp of an ionic compound. Acid-base titrations depend on the neutralization between an acid and a base when mixed in solution. The curve starts at a higher pH than a titration curve of a strong base; There is a steep climb in pH before the first midpoint; Gradual increase of pH until past the midpoint. Some Typical Conductometric Titration Curves are: 1. Titration curves for strong acid v weak base. Which sentence is false about indicator ? At the various points in your titration curve, list the major species present after the strong acid (HNO 3 , for example) reacts to completion with the weak base, B. Weak acid/strong base titration curve. ⚛ Before any strong base is added to weak acid : ⚛ Addition of strong base while weak acid is in excess : R.I.C.E. Let’s say that you want to titrate a 50.00 mL aliquot of 0.1000 M CH 3 NH 2 with a 0.1000 M solution of HCl and then construct the resulting titration curve. An acid-base titration involves strong or weak acids or bases. CC BY-SA 3.0. http://en.wikipedia.org/wiki/Strong_acid The weak-acid solution has a lower initial pH. The simplest acid-base reactions are those of a strong acid with a strong base. But the addition of sodium hydroxide also initially increases the concentration of acetate ions, some of which will react to reform some undissociated acetic acid molecules, thereby increasing the concentration of acetic acid molecules by a bit more. Titration boasts very practical and essential, though often overlooked, usage in the modern world. So, for 0.001 mol L-1 CH3COONa(aq), the pH at the equivalence point is 7.87, so we need an indicator that changes colour around pH = 7.87. This combination does not have a sharp end-point, so it is not used in analytical experiments Not applicable as not sharp end-point. Table to determine the equilibrium concentration of H+(aq). Therefore, the $\mathrm{pH}$ value starts rising much more rapidly than previously — as you would expect from the titration of a strong acid with a strong base. Several fruits, greens and dairy goods consist of some sort of acid. We could continue these calculations for the addition of 12.00 mL of 0.200 mol L-1 NaOH(aq), 13.00 mL, etc. At the equivalence point and beyond, the curve is typical of a titration of, for example, NaOH and HCl. 18.0 Ml O B.0.0 ML C. 10.0 Ml Bd. The simplest acid-base reactions are those of a strong acid with a strong base. Indicators: Methyl … One way to track a titration is to examine its pH curve. C) The titration of a strong acid with a strong base is a fast reaction whereas the titration of a weak acid with a strong base is generally a very slow reaction. Recent developments in chemistry written in language suitable for students. So once again we're putting pH in the Y axis, and down here in the X axis is the milliliters of base that we are adding. Calculate the pH of this solution (at 25°C): The pH of this titration experiment at the equivalence point is 8.87. Ø pKa is a pH at which the concentration of weak acid and its conjugate base will be in equimolar concentrations. • The pK a of the analyte will play an important role in the calculations. An aqueous solution of sodium hydroxide, NaOH(aq), is an example of a strong base. No consideration was given to the pH of the solution before, during, or after the neutralization. As the concentration of dilute acetic acid, CH3COOH(aq), increases the pH of the solution decreases because there will be a greater concentration of hydrogen ions, H+(aq), in solution. If one reagent is a weak acid or base and the other is a strong acid or base, the titration curve is irregular, and the pH shifts less with small additions of titrant near the equivalence point. In Brønsted-Lowry terms, we have a weak acid (CH3COOH(aq)) in equilibrium with its conjugate base (CH3COO-(aq)): which means that, for as long as the acetic acid (CH3COOH(aq)) is in excess (that is, NaOH(aq) is the limiting reagent), we have established a buffer solution. titration solution Weak Acid and Strong Base Titration Curve A weak acid only partially dissociates from its salt The pH will rise normally at first, but as it reaches a zone where the solution seems to be buffered, the slope levels out. 2 Materials Chemicals: Sodium carbonate, hydrochloric acid, sodium hydroxide and acetic acid. The Problem. In contrast to strong acids and bases, the shape of the titration curve for a weak acid or a weak base depends dramatically on the identity of the acid or the base and the corresponding \(K_a\) or \(K_b\). then for a strong acid - strong base titration at the equivalence point at 25 o C: pH = ½pK w = ½(-log 10 K w) = ½(-log 10 10-14) = 7 3. The Sharp Rise Is At 10.0 ML Marked Out Of 1.00 Flag Question 12 10 10 Ml Select One: ( A. Interpret titration curves for strong and weak acid-base systems; Compute sample pH at important stages of a titration; Explain the function of acid-base indicators; As seen in the chapter on the stoichiometry of chemical reactions, titrations can be used to quantitatively analyze solutions for their acid or base concentrations. In this section, we will explore the underlying chemical equilibria that … CC BY-SA 3.0. http://en.wikipedia.org/wiki/Alkali_salt The expression for the equilibrium constant for this hydrolysis reaction is given the symbol Kh, and equally it can also be given the symbol Kb : and since Kb(acetate ions) = Kw ÷ Ka(acetic acid), at 25°C, Kb(acetate ions) = (1.00×10-14) ÷ (1.80×10-5) = 5.56×10-10. Boundless vets and curates high-quality, openly licensed content from around the Internet. pH is the pH at the equivalence point of the neutralisation reaction. The pH rises more rapidly at the start, but less rapidly near the equivalence point. There is one more region of interest on this titration curve that we have not yet considered. the half-neutralisation point. We could continue these calculations for the addition of 2.00 mL, 3.00 mL, 4.00 mL, ... up to 9.00 mL of NaOH(aq). (Buffer is a solution which can resist the change in pH). Ø The titration curve of a weak acid reveals its pKa. Objectives: You will be able to: (1) determine the hydrogen ion concentration of a weak acid via titration against a strong base, (2) calculate the pH of a weak acid / strong base titration at the endpoint of a The values of the pH measured after successive additions of small amounts of NaOH are listed in the first column of this table, and are graphed in Figure 1, in a form that is called a titration curve. In a weak base-strong acid titration, the acid and base will react to form an acidic solution. The titration of a strong acid and weak base results in salt and water with a neutral or almost neutral pH at the equivalence point as this is where the number of moles in the strong acid equal the number of moles in the weak base. Acid-base titrations depend on the neutralization between an acid and a base when mixed in solution. A titration curve provides an idea regarding the equivalence point of an acid-base reaction, which is the exact phase in which the amounts of acid and base will be just precise for the reaction to occur. Any of the three indicators will exhibit a reasonably sharp color change at the equivalence point of the strong acid titration, but only phenolphthalein is suitable for use in the weak acid titration. This website seems to indicate that choice C is correct. This the reverse of the Kb reaction for the base A−.Therefore, the equilibrium constant for is K = 1/Kb = 1/(Kw/Ka (for HA)) = 5.4 × 107. Weak Base Strong Acid Titration Curve 13. Contrarily, this graph depicts a weak base’s titration. There are a number of differences between the titration curves for a strong acid versus the weak acid. Why is pH < 7.0 at the equivalence point of a weak base–strong acid titration? An acid–base titration is a method of quantitative analysis for determining the concentration of an acid or base by exactly neutralizing it with a standard solution of base or acid having known concentration. Acid-base titrations depend on the neutralization between an acid and a base when mixed in solution. I keep getting this question wrong, I think the last ones are right. If you need to sketch a rough titration curve for a weak acid - strong base titration, you will need to perform 4 calculations to locate 4 key features of the titration curve: Formic acid (methanoic acid), HCOOH(aq), is a weak acid (Ka = 1.80×10-4). Reaction of weak base and strong acid. The curve resembles the weak acid - strong base conductance curve in the previous section up to the end point for the titration. stoichiometryThe study and calculation of quantitative (measurable) relationships of the reactants and products in chemical reactions (chemical equations). As we shall see, the pH also changes much more gradually around the equivalence point in the titration of a weak acid or a weak base. At the equivalence point, 0.0400 L (40.00 mL) of NaOH(aq) had been added, if we add 1 more mL (0.001 L) then: n(NaOH in excess) = c × V(excess) = 0.100 × 0.001 = 1.00 × 10-4 mol, V(total) = V(acid) + V(all base) = 0.0200 + 0.041 = 0.061 L, [NaOH final] = n(NaOH in excess)/V(total) = (1.00 × 10-4)/0.061 = 1.64×10-3 mol L-1, [NaOH final] = [OH-(aq)] = 1.64×10-3 mol L-1, pOH = −log10[OH-(aq)] = −log10[1.64×10-3] = 2.79, Note that the line will have a gentle slope of increasing pH that cannot exceed 14 −log[0.100] = 13. Strong Acid with a Strong Base, e.g. In this section, we will explore the underlying chemical equilibria that … We can calculate the pH of the solution in the conical flask after each addition of NaOH(aq). CC BY-SA 3.0. http://en.wikipedia.org/wiki/Equivalence_point, http://en.wiktionary.org/wiki/stoichiometry, http://en.wikipedia.org/wiki/Acid-base_titration, https://www.boundless.com/chemistry/textbooks/boundless-chemistry-textbook/. titration solution Weak Acid and Strong Base Titration Curve A weak acid only partially dissociates from its salt The pH will rise normally at first, but as it reaches a zone where the solution seems to be buffered, the slope levels out. Protein can help develop and repair tissues like pores and skin and muscle and it can help deliver antibodies and … ⚛ When all the weak acid has been neutralised by all the strong base we calculate the pH of the aqueous salt solution: ⚛ Initial pH (pH < 7) : before any base is added the pH of the weak acid is dependent on: (b) value of Ka (which is also temperature dependent). If you do this, you would end up with the pH values listed in the table below: Plotting the points on a graph using the table above will result in a curve as shown below: Let's consider the various important features of the acetic acid - sodium hydroxide titration curve we plotted above. HCl with NaOH: Before NaOH is added, the conductance is high due to the presence of highly mobile hydrogen ions. During this titration, as the OH– reacts with the H+ from acetic acid, the acetate ion (C2H3O2–) is formed. Strong Acid-Weak Base Titrations | Introduction to Chemistry strong acid weak base titration curve. weak acid-strong base and weak acid-weak base titration, the salt that is formed may undergo hydrolysis and this may cause the pH not to be equal to 7 at the end-point. The weak-acid solution has a higher initial pH. Table to determine equilibrium concentrations of anion and weak acid. Calculating a Titration Curve for a Weak Acid - Strong Base Titration An aqueous solution of acetic acid (ethanoic acid), CH 3 COOH (aq), is an example of a weak acid. POINT OF EMPHASIS :The equivalence point for a weak acid-strong base titration has a pH > 7.00. Wikipedia As the [CH3COOH(aq)] decreases by a bit, and the [CH3COO-(aq)] increases by a bit, the [H+(aq)] decreases by a bit so the pH increases by a bit. The curve resembles the weak acid - strong base conductance curve in the previous section up to the end point for the titration. This is the resulting curve of a relatively strong acid’s titration. Titration Curve: [Reference Graph] The initial pH of the solution at the beginning of the titration is approximately that of the weak acid in water. (4) pH of the solution when strong base is in excess (approximately approaches pH of the strong base solution). Let's consider the green cross on the dark red line, x, on the titration curve above. Titration of strong acid with a strong base When NaOH titrated with the HCl then it will show the pH value 7 and the equivalent point will be the average distance of the curve. This is due to the production of conjugate base during the titration. This video shows how a titration curve is constructed using data from the titration of a weak base with a strong acid. In an acid-base titration, the titration curve reflects the strengths of the corresponding acid and base. Graph of pH versus volume of base that is added to the acid of constant volume or otherwise is called the pH titration curve. The pH of this solution at the equivalence point is due to the hydrolysis of the acetate ion (ethanoate ion), CH3COO-(aq) which releases hydroxide ions, OH-(aq), so the solution is basic: The greater the concentation of acetic acid used in the experiment, the greater the concentration of acetate ions produced at the equivalence point, so the greater the hydroxide ion concentration. Now, let's add 1.00 mL of 0.200 mol L-1 from the burette to the 10.00 mL of 0.200 mol L-1 CH3COOH(aq) in the conical flask. The X-axis Scale Goes From 0.0 ML To 20.0 Ml. Hundreds of compounds both organic and inorganic can be determined by a titration based on their acidic or basic properties. So, given a list of possible indicators such as the one below (in which the effective range is assumed to be ± 1): we could choose a suitable indicator for each of our CH3COONa(aq) solutions resulting from the titration of acetic acid with sodium hydroxide: Finally, we consider the indigo line on the titration curve above. Weak Acid Strong Base Titration Curve – pH is greater than 7 at the equivalence point 10. pH = pKa at one half of the equivalence point [latex]C_2H_3O_2^- + H_2O \rightarrow HC_2H_3O_2 + OH^-[/latex]. Kb is small so very little HCOO-(aq) hydrolyses: [OH-(aq)] = √Kb[HCOO-(aq)] = √(5.56×10-11 × 0.067) = 1.93×10-6 mol L-1, pOH = −log10[OH-(aq)] = −log10[1.93×10-6] = 5.71, Step 3: pH of the most effective buffer solution (pH = pKa), pH = pKa = −log10Ka = −log10(1.80×10-4) = 3.74. which occurs when half the acid has been neutralised, so the volume of NaOH(aq) added = half the volume at neutralisation: V(NaOH(aq)added) = ½ × 0.0400 L = 0.0200 L, Step 4: pH of the solution when strong base is in excess (approximately approaches pH of the strong base solution). Step 1: initial pH of weak acid before base is added, dissociation of formic acid: HCOOH(aq) → H+(aq) + HCOO-(aq)     Ka = 1.80×10-4, assume very little formic acid dissociates so [HCOOH(initial)] ≈ [HCOOH(equilibrium)], then, [H+(aq)] = √(1.80×10-4 × 0.200) = 6.00×10-3 mol L-1, pH = −log10[H+(aq)] = −log10[6.00×10-3] = 2.22, Step 2: pH of the salt solution at the equivalence point, neutralisation reaction: HCOOH(aq) + NaOH(aq) → HCOONa(aq) + H2O(l), n(HCOOH available) = n(NaOH added) = n(HCOONa(aq) produced), n(HCOOH available) = c × V = 0.200 × 20.00/1000 = 4.00 × 10-3 mol, V(NaOH added) = n(NaOH added)/[NaOH] = (4.00 × 10-3)/0.100 = 0.0400 L, V(total) = V(HCOOH) + V(NaOH) = 0.0200 + 0.0400 = 0.0600 L, [HCOONa] = n(HCOONa)/V(total) = (4.00 × 10-3)/0.0600 = 0.067 mol L-1, Hydrolysis of HCOO- (Na+ does not hydrolyse), HCOO-(aq) + H2O(l) ⇋ HCOOH(aq) + OH-(aq)     Kb = Kw/Ka = (1.00×10-14)/(1.80×10-4) = 5.56×10-11 (25°C). This equimolar concentration of a weak acid and its conjugate base can act as a buffer. However, the pH at the equivalence point does not equal 7. At 25°C the actual pH is determined by the concentration of the actic acid (and the value of its acid dissociation constant, Ka). Table to determine the equiliubrium concentrations of each species: and we can write an expression for the hydrolysis equilibrium constant, Kh, (which is equivalent to the base dissociation constant, Kb) and calculate the value of Kb (since Kb = Kw ÷ Ka): and use the equilibrium concentrations of each species to determine [OH-(aq)]: pOH = −log10[OH-(aq)] = −log10[6.19×10-11] = 10.21. The conductance of electrolytes depends on the number of ions and their speeds. d.pH = pka + log [conjugated base]/[conjugated acid] 7.When titration occur between Weak base and strong acid which indicator are used ? An aqueous solution of sodium hydroxide, NaOH (aq), is an example of a strong base. This is related to on the weak acid/strong base titration curve below, label the following points.. Wiktionary If we have 1.00 mol L-1 CH3COONa(aq), the pH at the equivalence point is 9.37, so we need an indicator that will change colour around pH = 9.37. The progress of … The titration curve demonstrating the pH change during the titration of the strong base with a weak acid shows that at the beginning, the pH changes very slowly and gradually. The pH rises more rapidly at the start, but less rapidly near the end point. bufferA solution used to stabilize the pH (acidity) of a liquid. Once complex is formed, the complex is stable and not further reaction takes place. The pH at the equivalence point does not equal 7.00 (pH > 7.00) for the weak acid titration. The equipment would be set up as in the diagram below: The NaOH(aq) is added 1.00 mL at a time to the CH3COOH. pHThe negative of the logarithm to base 10 of the concentration of hydrogen ions, measured in moles per liter; a measure of acidity or alkalinity of a substance, which takes numerical values from 0 (maximum acidity) through 7 (neutral) to 14 (maximum alkalinity). CC BY-SA 3.0. http://en.wikipedia.org/wiki/Equivalence_point pK a of an unknown acid or pK b of the unknown base. As the reaction begins, the pH starts increasing. Wikipedia Have a look at the following picture, that shows the titration curve for weak / strong acid titrated with strong base. The titration curve for a weak acid - strong base titration has a characteristic shape in which the following features can be identified: We can draw a reasonable sketch of a weak acid - strong base titration using these 4 calculations. 3. \[ \mathrm{HA}(aq) + \mathrm{OH^-}(aq) \rightleftharpoons \mathrm{H_2O}(l) + \mathrm{A^-}(aq)\] Titration Details. Now, how does a weak acid vs weak base titration curve look like? Conductometric Titration of strong acid and strong base: In a strong acid-strong base titration, the acid and base will react to form a neutral solution. The titration curve for a weak acid - strong base titration has a characteristic shape in which the following features can be identified: ⚛ Initial pH : before any base is added the pH of the weak acid is dependent on: (a) concentration of weak acid (b) value of K a (which is also temperature dependent) ⚛ Buffer zone (buffer region) of titration curve : (a) addition of strong base while weak acid is in excess … This is the currently selected item. (adsbygoogle = window.adsbygoogle || []).push({}); Want chemistry games, drills, tests and more? CC BY-SA 3.0. http://en.wiktionary.org/wiki/stoichiometry In the food industry, titration testing determines … This titration involved a weak acid with a K a value of 1.4*10-3 and the strong base MOH. So a new equilibrium position is established in which : Since the acid dissociation constant for acetic acid is given by the following expression: We can rearrange this expression as shown below to determine the concentration of hydrogen ions in this buffer solution (and hence the pH) : Note that [H+(aq)], and hence the pH of the solution, is determined by the ratio of [CH3COOH(aq)] to [CH3COO-(aq)]. Please do not block ads on this website. Weak acid by strong base titration curve : Let us take the titration of acetic acid by sodium hydroxide as typical example of a weak acid by a strong base NaOH + CH 3 COOH ↔ CH 3 COONa + H 2 O Calculation of the pH during the titration : The following Table shows the way that pH can be calculated before , at and after the equivalent point . In the beginning, the solution has a low pH and climbs as the strong base is added. If you add 50ml(1.00 M) = 0.05 moles of HCl to the base, the reaction in the previous step will consume all of the H +, leaving 0.100 - 0.050 = 0.050 moles of ClO-. Use a R.I.C.E. ⚛ After equivalence point (pH > 7): strong base is in excess and pH is dependent on: (1) initial pH of weak acid before base is added, (2) pH of the salt solution at the equivalence point, (3) pH of the most effective buffer solution (pH = pKa). For … Running acid into the alkali. Wikipedia This means that the solution at the equivalence point is made up of the salt named sodium acetate (sodium ethanoate), CH3COONa, dissolved in water. Distinguish a weak acid-strong base titration from other types of titrations. A conjugate acid will be produced during the titration, which then reacts with water to form hydronium ions. Acid is titrated with a base and base is titrated with an acid. The endpoint and the equivalence point are not exactly the same: the equivalence point is determined by the stoichiometry of the reaction, while the endpoint is just the color change from the indicator. When half the acetic acid has been neutralised then the concentration of the excess acetic acid is the same as the concentration of acetate ions in solution, and this leads to an interesting position: and if we take the negative log of both sides, then. Titration of strong acid with a strong base When NaOH titrated with the HCl then it will show the pH value 7 and the equivalent point will be the average distance of the curve. If one reagent is a weak acid or base and the other is a strong acid or base, the titration curve is irregular, and the pH shifts less with small additions of titrant near the equivalence point. The pH at the equivalence point does not equal 7.00. https://www.khanacademy.org/.../v/titration-of-a-weak-base-with-a-strong-acid The endpoint is usually detected by adding an indicator. a.Phenolphthalein give colourless solutions at pH 8.3-11.0 in acidic medium. Strong Acid Strong Base … Let us consider acid-base reaction which is proceeding with a proton acceptor. I am titrating it with a strong base. Please enable javascript and pop-ups to view all page content. equivalence pointThe point in a chemical reaction at which chemically equivalent quantities of acid and base have been mixed. For example, if 11.00 mL of 0.200 mol L-1 NaOH(aq) is added to 10.00 mL of 0.200 mol L-1 CH3COOH(aq) : Because the value of the equilibrium constant for the hydrolysis of acetate ions is very small, Kh = Kb = 5.56×10-10, we will ignore its contribution to the hydroxide ion concentration, and only consider the complete dissociation of sodium hyroxide to produce hydroxide ions and sodium ions as shown in the chemical equation below: So, [OH-(aq)] = [NaOH(aq)(after reaction)] = 9.52×10-3 mol L-1, pOH = −log10[OH-(aq)] = −log10[9.52×10-3] = 2.02. So, when 0.00 mL of NaOH(aq) has been added to 10.00 mL of 0.200 mol L-1 CH3COOH(aq) the pH of the solution is 2.72. CC BY-SA 3.0. http://en.wiktionary.org/wiki/pH Past the equivalence point for the neutralisation reaction, the addition of more weak base (NH 4 OH (aq) ) has little impact on the conductance of the solution since its dissociation is depressed by the presence of ammonium ions, NH 4 + (aq) , already present in the solution. Question: Not Yet Answered At What Point In The Following Titration Curve For A Weak Acid Being Titrated With A Strong Base Is The PH Equal To The Pk Of The Acid? Based on scientific researches, food … What equilibrium problem would you solve at the various points in your titration curve to calculate the pH? Ca+2 + EDTA-4 -----> … Wiktionary Examples from medical practice include intravenous fluid proportioning (blood vs. added medicine) and blood glucose level monitoring. Titration: Weak Acid with Strong Base We will consider the titration of 50.00 mL of 0.02000 M MES with 0.1000 M NaOH. H2SO4 and NaOH Titration Acid Base Neutralization Reaction – Double Replacement 15. The concentration of the base was 0.147 M. Initially 40.00 mL of a 0.0517 M solution of the weak acid was added to a beaker. So, a titration curve can be used to determine the pKa (an hence Ka) of a weak acid. Table to determine the equilibrium concentrations of all species as a result of the hydrolysis of acetate ions: Use Kb and equilibrium concentrations to calculate concentration of hydroxide ions, [OH-(aq)], which is equal to x: pOH = −log10[OH-(aq)] = −log10[7.46×10-6] = 5.13. Wikipedia 1. How to determine the pKa of a weak acid using titration curves 12. Table 1 sho… Figure 14.20 Titration curves for strong and weak acids illustrating the proper choice of acid-base indicator. This is the reaction of ethanoic acid vs ammonia. Sodium hydroxide, NaOH(aq), is a strong base. Calculate the intial concentration of acetate ions using the neutralisation reaction between acetic acid and sodium hydroxide: Use a R.I.C.E. H + (aq) + ClO-(aq)-> HClO (aq) Start with 100 ml(1.00 M) = 0.100 moles of ClO-. This time we are going to use hydrochloric acid as the strong acid and ammonia solution as the weak base. When 0.00 mL of NaOH(aq) has been added to 0.200 mol L-1 CH3COOH(aq) the pH of the solution is due to the dissociation of this weak acid. Classify each titration curve as representing a strong acid titrated with a strong base, a strong base titrated with a strong acid, a weak acid titrated with a strong base, a weak base titrated with a strong acid, or a polyprotic acid titrated with a strong base. The initial pH of the solution at the beginning of the titration is approximately that of the weak acid in water. Some content on this page could not be displayed. We have used different colours on the curve to differentiate the regions of the titration curve we will be discussing: First, consider the gold line on the titration curve. This conjugate base reacts with water to form a slightly basic solution. The titration of a weak base with a strong acid has similar features to the titration of a weak acid in a strong base but the curves sort of go in the opposite directions. Therefore, half the acid had been neutralised when half this volume of base had been added, that is, when 5.00 mL of NaOH(aq) had been added.