Thursday, June 9, 2022

Why is phenolphthalein used as an indicator in weak acid vs strong base titration?

Phenolphthalein is an organic compound with the formula C20H14O4. It belongs to the phthalene family and is a weak acid that can lose H+ ions in water. It comes in the form of fine crystalline, yellowish white to light orange powder. It is used as a component of the universal indicator, along with bromothymol blue, thymol blue, and methyl red.

The pKa of phenolphthalein is 9.3, and the pH range is 8.20 to 10.00. Over a range of acidic pH, the molecule has no color. At pH 8.2, it starts to turn pink, and at pH 10.00 and above, it turns a bright magenta color.

Why is phenolphthalein used in weak acid strong base titration?

Generally, phenolphthalein is used as an indicator in acid-base titration, particularly for the titration of strong bases-weak acids and strong acid-strong base titration. Depending on the acid and the base, the equivalence point (stoichiometric point) for the titrations between strong bases and weak acids is somewhere above pH 7.

Phenolphthalein indicator changes color around a pH of 8 to 10, which is right in the range of the equivalence point of these titrations, making them useful. It shows pink in basic solutions and colorless in an acidic medium.

Therefore, phenolphthalein is used as an indicator for titration of a weak acid and strong base such as acetic acid (CH3COOH) and sodium hydroxide (NaOH).
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Why phenolphthalein is used as indicator in titration?

A titration is a technique for determining the concentration of an unknown sample solution using a solution of known concentration. Generally, the titrant from a burette is added to an unknown quantity of the analyte, which pours into the conical flask until the reaction is complete. An indicator is often used to indicate the endpoint or equivalence point.

What is a phenolphthalein indicator?

Phenolphthalein, (C20H14O4), an organic compound of the phthalene family, is a weak acid, which can lose H+ ions in solution. It is a thin, crystalline, and yellowish-white to light orange powder.

Phenolphthalein has a pKa of 9.3 and 8.20 to 10.00 is the pH range for the phenolphthalein indicator. The molecule is colourless over an acidic pH range, beginning to turn pink at pH 8.2 and becoming vivid magenta at pH 10.00 and above.

The most common application of phenolphthalein is as an indicator in acid-base titrations. It, along with thymol blue, bromothymol blue, and methyl red, is used as a component of the universal indicator.

Why is phenolphthalein used as an indicator in titration?

Phenolphthalein is used as an indicator in acid-base titration because it changes color between 8.3 and 10 pH, is economical, readily available, easily soluble, and has an endpoint that is very recognizable from either direction.

The pH of the equivalence point for an acid-base titration determines which indicator to use. Choose an indicator that changes colour at or near the equivalence point (Stoichiometric point). At this point, the titration curve will be steep, and we will get a sharp endpoint of the reaction.

When the pH rises above 07.00, phenolphthalein changes color. As a result, it works well as an indicator for the titration of strong acids and bases. It can also be used to titrate weak acids and strong bases with equivalence point above pH 07.00.

Because the equivalence point is below pH 07.00, it is not a good choice for titrations between a strong acid and a weak base. In this case, methyl orange is more suitable.

Frequently Asked Question (FAQ):

How can phenolphthalein change color?

Phenolphthalein is an indicator that changes colour depending on whether it meets an acid or a base. The phenolphthalein ion is pink, and the phenolphthalein molecule is colorless. When a base is introduced to phenolphthalein, the molecule ⇌ ions equilibrium shifts to the right, resulting in increased ionisation as the H+ ions are removed.

Which indicator is used for weak acid and a strong base?

Since the phenolphthalein indicator changes rapidly at the equivalence point, it is a good choice for weak acid and strong base titrations.

Phenolphthalein is which type of indicator?

Phenolphthalein is a synthetic pH indicator used in acid-base titration. It is a colorless, weak acid that is most commonly used in titration as an indicator to indicate the endpoint of the titration. Because this molecule dissociates to produce pink color when dissolved in water, the formation of pink color indicates the endpoint of the reaction.

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Wednesday, June 8, 2022

How to find first and second equivalence points

Titration is a method for determining the concentration of an analyte using a solution of known concentration (Titrant). The acid-base titration is a quantitative technique for determining the concentration of acid/base through neutralization. Typically, an indicator is used to detect the endpoint of the titration, which causes the solution's color to change.

The equivalence point (also known as the stoichiometric point) of a chemical reaction is the point where chemically equivalent amounts of reactants are mixed. According to the chemical process, the equivalence point for an acid-base reaction is where the moles of acid and moles of base neutralize each other.

The first equivalence point occurs when the first hydrogen ion H+ from the initial volume of acid is neutralized by the titrant base.
H2A + OH- →H2O+HA-
At the first equivalence point, one mole of acid reacts with one mole of a base.

The second equivalence point is the point in a titration at which both hydrogen ions H+ from the initial volume of acid have been neutralized by the titrant base.
H2A+2OH−→2H2O+A2+
At the second equivalence point, one mole of acid reacts with two moles of a base.

The titration curve is shown in the diagram below.

How to find first and second equivalence points

The volumes of strong base necessary to reach the first and second equivalence points are almost identical. The only difference between each equivalence point is the height of the steep rise.


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What is the first equivalence point in titration?

Titration is a technique for determining the concentration of an unknown analyte (Titrand) using a known concentration solution (Titrant). The acid-base titration is a type of quantitative method for determining acid or base concentrations by neutralizing with a known concentration of acid or base. Generally, an indicator is used to detect the endpoint of the titration, which changes the color of the solution.

The point in the titration at which the amount of titrant added is sufficient to neutralize the analyte solution is referred to as the equivalence point. At the equivalence point, the number of moles of the acid is equal to the number of moles of the product, resulting in the formation of a salt product and water.

The equivalence point, or stoichiometric point, is the point where adding enough base to neutralize the acid to form a salt. At the equivalence point, there are an equal amount of moles of acid and base.

First equivalence point in titration:

The first equivalence point is the point of the titration in which the first hydrogen ion H+ from the initial volume of acid is neutralized by the base employed as the titrant.
H2A + OH- →H2O+HA-
At the first equivalence point, one mole of acid reacts with one mole of the base.

An example of the first equivalence point in titration:

Titration of diprotic acids such as sulfuric acid (H2SO4) and carbonic acid (H2CO3). In water, a diprotic acid dissociates in two stages.

From the beginning to the first equivalence point, the equations for acid-base reactions between a diprotic acid, H2X, and NaOH base.

All H+ ions from the first dissociation have reacted with NaOH base at the first equivalence point, and all H+ ions from both reactions have reacted at the second equivalence point. Diprotic acid titration curves have two equivalence points due to the successive dissociations,

Why is the pH of the first equivalence point, of a titration of polyprotic acid?

The first equivalence point in the titration of phosphoric acid (H3PO4) with sodium hydroxide (NaOH) has a pH of around 05.
For example:
H3PO4 is a weak triprotic acid. (pKa 1 is 2.16, pKa 2 is 7.16, and pKa 3 is 12.3).
The first equivalent point is: H3PO4 + NaOH → NaH2PO4 + H2O
The pH of the resultant solution is calculated as follows: 
pH = (pKa1 + pKa2)/2 = 4.66
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Tuesday, June 7, 2022

Difference between equivalence point and half equivalence point

Titration is a method for determining the unknown concentration of an analyte (Titrand) using a solution of known concentration (Titrant). The titrant is typically added to a known amount of the analyte using a burette until the reaction is completed. Often, a visual indicator is used to indicate the end-point of a reaction. Since the volume of the titrant is already known, the concentration of the analyte can be easily determined using the titration formula.


What is half equivalence point?

The half equivalence point is the midway point between the equivalence point and the starting point in a titration. It is also known as the midpoint of titration. At this moment, the pH of the analyte solution is equal to the dissociation constant, or pKa, of the acid employed in the titration. The half equivalence point happens at one-half the volume of the first equivalence point.

If there are several equivalence points in the titration, the same number of half equivalence points exists. For example, the second-half equivalence point occurs between the first and second equivalence points. Because, at the half equivalence point, the pKa of the acid is equal to the pH of the solution, determining the half equivalence point is rather simple.

What is the equivalence point?

The equivalency point is also known as a stoichiometric point, it is the point in the titration process where the chemical reaction in the titration mixture ends. In a titration, the equivalence point is the actual point of the desired chemical reaction in the reaction mixture.

Typically, titrations are used to determine the concentration of a substance in a sample solution. The equivalence point can be determined by the pH change, color change, precipitation formation, temperature change, conductivity change, etc..

Difference between equivalence point and half equivalence point:

The major difference between the half equivalence point and equivalence point is that the half equivalence point is the midpoint between the beginning point and equivalence point of a particular titration, whereas the equivalence point is the point where the chemical reaction between titrant and titrand ends.

Frequently Asked Question (FAQ): 

What does the half equivalence point mean?

The half equivalence point is where exactly half of the acid in the buffer solution has reacted with the titrant.

Are there two equivalence points with diprotic acid?

Yes, the number of equivalence points on a titration curve for a polyprotic acid corresponds to the number of acidic protons in the acid. Since a diprotic acid is titrated using two acidic protons, the titration curve contains two equivalence points.

Why is the pH equal to the pKa at the half equivalence point?

At the half-equivalence point, half of the acid is neutralized; therefore the amount of salt produced is half that of the acid; the concentrations of salt and acid are equal. Now, this solution is a buffer solution, and when the Henderson-Hasselbalch equation is used, the log value becomes zero.
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Endpoint and equivalence point in chemistry

In analytical chemistry, we use titration to determine acids, bases, reductants, oxidants, metal ions, and a variety of other species. Throughout the process of titration a chemical reaction occurs. In this case, an analyte reacts with a titrant, which is a standard reagent filled in the burette.

As a reference material in titrimetric methods, we sometimes use a primary standard, which is a highly pure and stable solution. To findout the endpoint of the reaction, we use an indicator. However, this is not the point at which the chemical process ends. The equivalence point is the actual point.

What is an endpoint?

Endpoint refers to the point in the titration process where the color of the indicator changes. For example, when Eriochrome Black T (EBT) is used as an indication in complexometric titration, the color changes from wine red to blue at the endpoint.

What is an equivalence point?

The point in the titration process where the chemical reaction in the titration mixture ends is called the equivalence point. It is also known as a stoichiometric point in titration. pH change, color change, precipitation formation, temperature change, and conductivity change are all methods for establishing the equivalence point.

How does the equivalence point differ from the endpoint and which comes first during titration?

There are two important stages, known as the endpoint and equivalence point, that are reached during the process. In a titration, an equivalence point is a point where the added titrant is chemically equivalent to the sample analyte. The endpoint, on the other hand, is the point where the solution changes color.

The major difference between equivalence and endpoint is that the equivalency point is the point at which a chemical reaction comes to an end, whereas the endpoint is the point at which color changes. The equivalence point comes before the endpoint.

What is the difference between endpoint and stoichiometric point?

The equivalence point is the common name for the stoichiometric point, and the differences between them have already been described above.

Why does the endpoint occur after the equivalence point?

Because a chemical reaction always occurs before a color change, the endpoint appears soon after the chemical reaction reaches the equivalence point. The color changes at the point where the pH of the titration solution becomes basic. Therefore, the endpoint can be determined following the complete neutralization at the equivalence point.

What is the midpoint of titration?

It is a point at which precisely enough acid/base has been introduced to neutralize one-half of the acid/base that was initially present and occurs halfway to the equivalence point.

In other words, the point at which half of the analyte is neutralized by the added titrant is referred midpoint of titration.

Is it possible for the endpoint and equivalence point to be the same?

Although endpoints are often referred to as equivalence points, the two terms are not the same. Since the difference between an equivalent point and an endpoint is minimal, they can be regarded as identical for laboratory purposes.

What is the pH at the endpoint of a titration?

The pH at the endpoint of a titration involving a strong acid and a strong base will be 07.00, pH > 07.00 when a weak acid is titrated with a strong base, and pH<7 when a weak base is titrated with a strong acid.

Is the endpoint always after the equivalence point?

The endpoint of the titration comes is either almost or after the equivalence point and the equivalence point of the titration comes either almost with the endpoint or before the endpoint.
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Saturday, June 4, 2022

What is equivalence point in chemistry?

Titration is an analytical chemistry technique used to determine the concentration of unknown sample solutions using solutions of known concentration. In the titration technique, the solution of known concentration is known as the titrant which is filled in the burette and the solution of unknown concentration is known as the analyte which is poured into a conical flask.

Endpoint and equivalence point are two different important stages that occur in the titration process. Numerous students mistakenly believe that the equivalence point and the endpoint of the titration are the same, although they are not. The endpoint is the moment at which an indicator changes the color of the solution. More often than not, the color change takes place after the equivalence point has been reached.

Define equivalence point in titration:

“It is a point in a titration, at which amount of titrant added is just sufficient to neutralize the analyte solution completely”

Equivalence point in titration?

The equivalence point of a chemical reaction is the point at which the number of moles of substance contained in the sample is stoichiometrically equal to the amount of titrant added. The minimum amount of titrant is required to completely neutralize or react with the analyte. In the titration of a diprotic acid, there exist many equivalence points that are multiples of the initial equivalence point.
equivalence point

It is also known as the stoichiometric point since it is the point at which moles of acids equal the amount of base needed to neutralize them. The equivalence point comes either closer to an endpoint or before an endpoint. This gives the point where the reaction ends.

Note that this does not mean that the ratio of acids and bases is equal to 1:1. The ratio is determined by the acid-base chemical equation in its balanced form. This does not necessarily mean that the acid-base ratio is 1:1. The ratio is calculated by the chemically balanced acid-base equation. The ratio is estimated by the balanced acid-base chemical equation.

Example of equivalence point:

Consider the sodium hydroxide (NaOH) and hydrochloric acid (HCl) titration as an example of an acid-base reaction. One mole of NaOH and one mole of HCl react chemically to form salt and water.
HCl + NaOH → NaCl + H2O

During titration, a prepared solution of NaOH is added gradually to a sample solution containing HCl and an appropriate indicator. The sodium hydroxide begins to react with the hydrochloric acid of the sample. When enough sodium hydroxide has been added to the sample to react with all of the hydrochloric acid, the equivalence point has been reached.

Methods of determining the equivalence point:

There is a different method that used to determine the equivalence point is as follows.
  • Color change
  • pH indicator
  • Precipitation
  • Conductance
  • Isothermal colorimetry
  • Thermometric titrimetry
  • Spectroscopy

What is half equivalence point?

The halfway between the equivalence point and the starting point in a titration is known as the half equivalence point. In an acid-base titration, the half-equivalence point is where the concentration of an added base equals half of the initial acid concentration. The half-equivalence point is also known as the midpoint of titration. The half equivalence point is fairly simple to determine as the pKa of the acid is equal to the pH of the solution at this point.

Why do diprotic acids have two equivalence points?

This is due to the two ionizing hydrogen’s in the acid do not dissociate from the acid at the same time. Protons are usually donated in steps by diprotic acids. As a result, the acid will have two acid dissociation constants, the second of which will be lower than the first.

What species are present at the equivalence point?

Only neutral ions (the cation from the strong base and the anion from the strong acid) and water are present in the solution at the equivalence point. Salt and water are present at the point of equivalence in acid-base titrations.
 

Frequently Asked Question (FAQ):

Why is the point in the titration when neutralization occurs called the equivalence point?

Because this is the point in a titration where the relative amounts of each component in the chemical reaction are precisely defined by the coefficients in the balanced chemical equation, it's called the equivalence point.

Is the equivalence point always 7?

In a strong acid-strong base titration, the equivalence point always occurs at pH=7. It is greater than 7 for a weak acid-strong base, and less than 7 for a strong acid-weak base because only the conjugate acid is present and it’s around about 7 for the weak acid-weak base.

Why is the pH at the equivalence point not always equal to 7 in a neutralization titration? When would it be 7?

Titration is a process in which an acid and a base react to neutralize each other. However, not all of the salts that formed are neutral. When a strong acid with a weak base, will give is a slightly acidic salt, likewise, a weak acid with a strong base gives a slightly basic salt.

Consider the reaction of acetic acid (acetic acid), a weak acid, with a strong base, such as sodium hydroxide (NaOH).

A salt, sodium acetate (C2H3NaO2), and water (H2O) are generated during the neutralization reaction. As a base, the acetate ion reacts with water to produce CH3COOH and OH- CH3COO- + H2O → CH3COOH + OH- The reaction of the acetate ion raises the pH of the solution from 7-8. The pH of the solution is increases from 7.0 by this acetate ion reaction. Because the conjugate base of a strong acid is strong and weak to dissociate water, the pH for strong acid strong base titrations is 7.


People also ask:

How do you find the equivalence point?
What is equivalence point in equilibrium?
Why is it called the equivalence point?
How do you know when an equivalence point is reached?
Why isnt the pH at the equivalence point always equal to 7?
What is the pH at the first equivalence point?
How do you find pH from equivalence point?
pH at equivalence point weak acid-strong base


References:
  • Wikipedia contributors. "Equivalence point." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 10 Dec. 2021.
  • Vogel, A.I.; J. Mendham (2000). Vogel's Textbook of Quantitative Chemical Analysis (6th ed.).
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Friday, June 3, 2022

What is the purpose of acid-base titration?

Acid–base titration is a quantitative analytical technique for estimating the concentration of an acid or base by neutralizing it with a known-concentration standard solution (Titrant) of acid/base.

Generally, the standard solution of known concentration which is filled in the burette is added dropwise in the sample solution which is poured into the conical flask. To detect the endpoint an indicator is added that changes the color of the solution. There are four types of acid-base titration, including strong acid-strong base, strong acid-weak base, weak acid-strong base, and weak acid-weak base.

MCQ: What is the main purpose of acid-base titrations?

A: To test if reactants react
B: To test the quality of reactants
C: To calculate the concentration of an unknown analyte
D: To calculate the concentration of known analyte

The correct answer is option C: To calculate the concentration of the unknown analyte.  

Acid-base titrations are most commonly used to determine the amount of an unknown acid or base in an analysis. It is also used in pharmaceutical applications, environmental analysis, and quantitative chemical analysis.



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Thursday, June 2, 2022

Why no indicator is suitable for weak acid and a weak base

An acid-base titration is a quantitative analysis technique used to estimate the concentration of an acid/base by neutralizing it with a known concentration standard solution of acid or base. It is classified as a strong acid-strong base, weak acid-strong base, strong acid-weak base, and weak acid-weak base.

From the point of view of chemical analysis, the method of titrating a weak base with a weak acid is not useful. Because of their low Ka/Kb values, any dissociation would be minor, necessitating the use of a large amount of titrant as well as consideration of chemical kinetics.

As well as when titrating a weak acid with a weak base, no indicator is suitable. Since the pH shift is very slow and close to the equivalence point, a weak acid solution cannot be titrated with a weak base using an indicator to find the endpoint.

At the equivalence point of a titration between a weak acid and a weak base, the pH does not change sharply. The pH varies gradually throughout a range of pH values. Therefore, no usable indicator exists for this type of titration.

Below is the titration curve for the 0.1 M ethanoic acid (CH3COOH) with 0.1 M ammonia solution (NH3) titration.
Why no indicator is suitable for weak acid and a weak base

In the vicinity of the equivalence point, the slope of the titration curve is quite large for the strong acid/base case and much less for the weak acid/strong base case. In a weak acid/weak base titration, the slope of the titration curve would be substantially less. In this example, potentiometric techniques would be needed to find the endpoint. Chemical indicators, which typically show a color change at a pH change of two units, would be ineffective.

Assertion:
The titration curve for weak acid and the weak base has no sharp changes. For this titration, no suitable indicator is present.

Reason:
The indicator should change its color sharply for the indication of the reaction to be complete, so its pH range lies perfectly within the sharp change to avoid an experimental error.
  • A. Both assertion and reason are correct and reason is the correct explanation for assertion
  • B. Both assertion and reason are correct but reason is not the explanation of assertion
  • C. Assertion is correct but reason is incorrect
  • D. Assertion is incorrect but reason is correct
Correct answer is option A.



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Can you use an indicator for weak acid and weak base?
Which indicator is best for weak acid and weak base?
Why weak acids and bases are not used as standard reagents?
Is a suitable indicator for the titration of a strong acid and a weak alkali?
Can indicators be weak bases?
Why phenolphthalein and methyl orange are inappropriate.
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Wednesday, June 1, 2022

Why is titration between a weak acid and a weak base not possible?

An acid-base titration is a type of titration in which the concentration of an acid/base is determined by titrating it against a known concentration of a base/acid. In solution, a strong acid/base dissociates completely into ions. Therefore we see the titration curve since this is not the case with mild acid/base.

When a weak acid is titrated with a weak base, the neutralization reaction occurs, depending on the pKa, pH, and pkb. As a result, it will be challenging to obtain the titration curve. Furthermore, once the weak acid and weak base are combined, the concentration of the dissociated and dissociated species cannot be estimated. 

In this situation, the complete dissociation of strong acids and bases is useful. They always completely dissociate in solution. There is no clear way to measure the concentration of a standard to titrate against an unknown weak acid/base, the entire experiment titration can fail.

Why weak acids cannot be used as a titrant in the titrations?

Since the pH shift is too gradual around the equivalence point of the reaction, a weak acid solution cannot be titrated with a weak base to determine the end-point.

Before, during, and after the equivalence point, weak acid and weak base always act as a buffer. Consequently, we don't get a steep section in the titration curve, or a sharp change in the solution’s pH around the equivalence point, and we can't choose an appropriate indicator.

What happens when a weak acid and a weak base react?

When a strong acid and a strong base are mixed, they will completely ionize, resulting in salt and water. Weak acids and bases, on the other hand, only partially ionize. As a result, mixing them usually results in a reversible reaction that forms a conjugate acid and a base as products.

Why should colorimetric titration of a weak acid with a weak base not be done in the laboratory?

When a weak acid reacts with a weak base, the equivalence point will be basic if the base is stronger and acidic if the acid is stronger, and the equivalence pH will be neutral if both are of equal strength. On the other hand, weak acids are rarely titrated against weak bases because the color change exposed by the indicator is often sharp, as a result, it's difficult for the observer to notice the color change.



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Why weak acids and bases are not used as standard reagents?
Which titration is used for weak acid and weak base?
What happens when a weak acid and weak base react?
Can you titrate a weak acid?
Why phenolphthalein cannot be used for titrating a weak base like hco3?
Is it possible to perform a titration of a weak acid with a weak base why OR why not?
Why is it difficult to do a titration of a weak acid and a weak base
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Why are strong acids generally used as standard solutions in acid-base titrations?

An acid-base titration is a quantitative analysis for estimating the concentration of an acid/base that has been suitably neutralized with a standard solution of a known concentration of acid or base. The endpoint and progress of the acid-base reaction are monitored using a pH indicator. Titration can be done with practically any chemical reaction that has a known balanced chemical equation.

Why are strong acids generally used as standard solutions in acid base titration?

  1. The salts of strong acids do not hydrolyse
  2. The pH at the equivalence point will always be 7
  3. They can be used to titrate both strong and weak bases
  4. Strong acids form more stable solutions than weak acids

The correct option is 3: They can be used to titrate both strong and weak bases

Explanation:

Strong acids are generally used as standard solutions in acid-base titrations since strong acids can react with both strong and weak bases, they are commonly employed as standard solutions in acid-base titrations.

The following are some examples of strong acids used in the acid-base titration.
  • Hydrochloric acid (HCl)
  • Sulfuric acid (H2SO4)
  • Nitric acid (HNO3)
  • Perchloric acid (HClO4)
  • Hydrobromic acid (HBr)
  • Hydroiodic acid (HI)
  • Chloric acid (HClO3)
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Tuesday, May 31, 2022

Why is a weak acid best titrated with a strong base?

An acid-base titration is a type of titration used to determine the concentration of an acid or base by neutralizing the acid or base with a known concentration of acid or base. Strong acid-strong base, weak acid-strong base, strong acid-weak base, and weak acid-weak base are the types of acid base titration.

In the titration of a weak acid with a strong base, protons are transferred directly from the weak acid to the hydroxide ion, in which the titrant is a strong base and the analyte is a weak acid. During titration, a titration curve indicates the strength of the corresponding acid and base as well as the pH change.

The titration curve showing the pH change throughout the titration of a strong base with a weak acid shows that initially, the pH changes extremely slowly and gradually. As the titration approaches the equivalence point, this indicates the formation of a buffer system. At the equivalence point and beyond, the curve is typical for titration of, for example, sodium hydroxide (NaOH) and hydrochloric acid (HCl). When there is an excess of NaOH, the pH change is the same as in any NaOH-dominated system. Generally phenolphthalein indicator is used for the titration of weak acids and strong bases.
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What will be the pH at the equivalence point of strong base weak acid titration?

In a titration, the equivalence point occurs when the amount of titrant added is sufficient to neutralize the analyte solution. At this point, the number of moles of titrant (standard solution) equals the number of moles of the unknown concentration solution.

What will be the pH at the equivalence point of strong base weak acid titration?

In the titration of a weak acid with a strong base, protons are transferred directly from the weak acid to the hydroxide ion.

In a titration of a weak acid with a strong base, the endpoint point is shifted from neutralization to the pH of the strong reagent (base). The equivalence point is reached when the moles of acid added stoichiometrically balances the moles of base added. In a titration of a weak acid with a strong base, the pH of the solution at the equivalence point is greater than 7.

For example, the reaction of the weak acid, acetic acid (CH3COOH) with a strong base, sodium hydroxide (NaOH).

What will be the pH at the equivalence point during the titration of a 1000 ml of 0.2 M solution of CH3COONa with 0.2 M solution of HCl?

  • A: 3+log√2
  • B: 3−log2
  • C: 3−log√2
  • D: 3+log2
The correct answer is option C: 3−log√2
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