18. Aqueous Equilibrium

Acid and Base Titration Curves

Acid-Base Titration

The samples of nitric and acetic acids shown here are both 
titrated with a 0.100 M solution of NaOH(aq).
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/1c060c5c82e924b2-1667315116216.jpg" alt="" />
Determine whether each of the following statements concerning 
these titrations is true or false. 
(a) A larger volume of NaOH1aq2 is needed to reach the 
equivalence point in the titration of HNO3.

On the same graph, sketch pH titration curves for the titra-tion of (1) a strong acid with a strong base and (2) a weak acid with a strong base. How do the two curves differ with respect to the following? 
(a) The initial pH

Consider the curve shown here for the titration of a weak
monoprotic acid with a strong base and answer each
question.
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/dd610639a7f7953c-1660313595460.jpg" alt="" />
d. At what volume of added base is the pH calculated by working
an equilibrium problem based on the concentration and
Kb of the conjugate base?

The following questions refer to the titration curve given below.1) The titration curve shows the titration of    a) a strong acid with a strong base    b) a weak acid with a strong base    c) a strong base with a strong acid    d) a weak base with a strong acid      2) Which point on the titration curve represents a region where a buffer solution has formed

The graphs labeled (a) and (b) show the titration curves for two
equal-volume samples of monoprotic acids, one weak and one
strong. Both titrations were carried out with the same concentration
of strong base.
(a) 
(b) 
(i) What is the approximate pH at the equivalence point of
each curve?

Match the following descriptions of titration curves
with the diagrams: (a) strong acid added to strong base. [Section 17.3]
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/6809196d319a1d3b-1667236179913.jpg" alt="" />

An indicator represents a weak acid or base in low concentration that changes color in an acid base titration. An&#160;indicator shows us the location of our endpoint, which is located near our equivalence point.&#160;

(a) By titration, 15.0 mL of 0.1008 M sodium hydroxide is needed
to neutralize a 0.2053-g sample of a weak acid. What is the molar
mass of the acid if it is monoprotic?

The following plot shows two pH titration curves, each representing the titration of 50.0 mL of 0.100 M acid with 0.100 M NaOH:
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/5fc5acc9c1a8e9a1-1673014625164.jpg" alt="" />.
(b) What is the approximate pH at the equivalence point for each of the acids?

Understanding an Acid–Base Titration Curve

Predict whether the equivalence point of each of the following 
titrations is below, above, or at pH 7: (c) pyridine titrated with nitric acid.

First:34.3 mL, Second:34.3 mL, Third:34.3 mL

First:34.3 mL, Second:68.6 mL, Third:102.9 mL

First:34.3 mL, Second:68.6 mL, Third:137.2 mL

First:105 mL, Second:210 mL, Third:315 mL

Consider the titration of 60.0 mL of 0.200 M H3PO3 solution with 0.350 M potassium hydroxide, KOH solution. How many milliliters of base would be required to reach each of its equivalence points?&nbsp;

Assume that 30.0 mL of a 0.10 M solution of a weak base B 
that accepts one proton is titrated with a 0.10 M solution 
of the monoprotic strong acid HA. (a) How many moles of 
HA have been added at the equivalence point?

Consider the titration of 40.0 mL of 0.0800 M HCl with 0.0160 M Ca(NH2)2.b) What is the pH of this solution

A 0.229-g sample of an unknown monoprotic acid is titrated 
with 0.112 M NaOH. The resulting titration curve is shown here. 
Determine the molar mass and pKa of the acid.
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/8c5a26212c509062-1660313975568.jpg" alt="" />

Consider the titration curves (labeled a and b) for two weak
acids, both titrated with 0.100 M NaOH.
(a) <img src="https://lightcat-files.s3.amazonaws.com/problem_images/be01012c6b88a487-1660314564260.jpg" alt="" />
(b) <img src="" alt="" />
(i) Which acid solution is more concentrated?

The following pictures represent solutions at various stages in the titration of a weak base B with aqueous HCl. (Cl- ions and solvent water molecules have been omitted for clarity.)
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/d9826aecf122d683-1673036872864.jpg" alt="" />.
(b) Is the pH at the equivalence point more or less than 7?

Titration curves help us to understand the neutralization occurring between an acid and base in order to identify the equivalence point.&#160;

Is the pH greater than, equal to, or less than 7 after the neutralization of each of the following pairs of acids and bases?
(a) NaOH and benzoic acid (C6H5CO2H)

The equivalence point is when the moles of acid and base titrating are equal in amount.&#160;

The distinctive odor of vinegar is due to acetic acid, CH3COOH,
which reacts with sodium hydroxide according to:
CH3COOH1aq2 + NaOH1aq2¡ H2O1l2 + NaCH3COO1aq2
If 3.45 mL of vinegar needs 42.5 mL of 0.115 M NaOH to
reach the equivalence point in a titration, how many grams
of acetic acid are in a 1.00-qt sample of this vinegar?

The equivalence point was reached in titrations of three unknown acids at pH 9.16 (acid A), 8.88 (acid B), and 8.19 (acid C). 
(a) Which is the strongest acid?
(b) Which is the weakest acid?

Which of the following mixtures has the highest pH?
(a) Equal volumes of 1.0 M HCl and 1.0 M NaOH 
(b) Equal volumes of 0.1 M HNO3 and 0.1 M KOH 
(c) Equal volumes of 0.1 M HCN and 0.1 M NaOH 
(d) Equal volumes of 0.1 M NaF and 0.1 M HCl

Predict whether the equivalence point of each of the following
titrations is below, above, or at pH 7: (a) formic acid
titrated with NaOH.

Basic Principles of Acid-Base Titrations

The accompanying graph shows the titration curves for two
monoprotic acids. (d) Estimate the pKa of the weak acid.
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/e08dd41de99d4b33-1667831344889.jpg" alt="" />

Is the pH greater than, equal to, or less than 7 after the neutralization of each of the following pairs of acids and bases?
(c) KOH and HI

The following figure represents solutions at various stages
of the titration of a weak acid, HA, with NaOH. (The Na+
ions and water molecules have been omitted for clarity.) To
which of the following regions of the titration curve does
each drawing correspond: (b) after addition of NaOH but before the equivalence point? [Section 17.3]
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/6cbaccacc51d6d25-1667234499678.jpg" alt="" />

The Equivalence Point

How many milliliters of 0.105 M HCl are needed to titrate each
of the following solutions to the equivalence point: (b) 22.5 mL of 0.118 M NH3?

Consider the curve shown here for the titration of a weak base
with a strong acid and answer each question.
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/95ae7c7ae471b936-1674575025504.jpg" alt="" />
d. At what volume of added acid is the pH calculated by working
an equilibrium problem based on the concentration and
Ka of the conjugate acid?

Compare the titration of a strong, monoprotic acid with a 
strong base to the titration of a weak, monoprotic acid with 
a strong base. Assume the strong and weak acid solutions 
initially have the same concentrations. Indicate whether 
the following statements are true or false. (a) More base is
required to reach the equivalence point for the strong acid 
than the weak acid.

Consider the titration curves (labeled a and b) for two weak 
bases, both titrated with 0.100 M HCl. 
(a) <img src="https://lightcat-files.s3.amazonaws.com/problem_images/1205c3a8f6fe909c-1660314406069.jpg" alt="" /> 
(b) <img src="" alt="" /> 
(ii) Which base has the larger Kb?

Assume that 30.0 mL of a 0.10 M solution of a weak base B
that accepts one proton is titrated with a 0.10 M solution
of the monoprotic strong acid HA. (c) Is the pH 7, less than 7, or more than 7 at the equivalence point?

Predict whether the equivalence point of each of the following
titrations is below, above, or at pH 7: (b) calcium hydroxide titrated with
perchloric acid.

The graphs labeled (a) and (b) show the titration curves for two
equal-volume samples of monoprotic acids, one weak and one
strong. Both titrations were carried out with the same concentration
of strong base.
(a) <img src="https://lightcat-files.s3.amazonaws.com/problem_images/f8092c44f2327468-1661444418387.jpg" alt="" />
(b) <img src="" alt="" />
(ii) Which graph corresponds to the titration of the
strong acid and which one to the titration of the weak
acid?

An indicator, like a buffer, has an optimal range in which it works most effectively:

pka +/-&#160;1.&#160;

17.2 Titrations and Titration Curves | General Chemistry

In a typical titration we begin with an acid or base and slowly add either a Strong Acid or Strong Base.&#160;

Predict whether the equivalence point of each of the following
titrations is below, above, or at pH 7: (b) NH3 titrated with HCl.

Which data set, of the two graphed here, would you expect
to observe from a titration like that shown in Figure 4.18?
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/e8a689eb96e93272-1661439766241.jpg" alt="" /><img src="https://lightcat-files.s3.amazonaws.com/problem_images/c419ff7c88d2e250-1661439790328.jpg" alt="" />

A sample of 0.2140 g of an unknown monoprotic acid was
dissolved in 25.0 mL of water and titrated with 0.0950 M
NaOH. The acid required 30.0 mL of base to reach the
equivalence point. (a) What is the molar mass of the acid?

Consider the titration curves (labeled a and b) for two weak 
acids, both titrated with 0.100 M NaOH. 
(a) <img src="https://lightcat-files.s3.amazonaws.com/problem_images/8f983a885fb363ce-1660313791606.jpg" alt="" /> 
(b) <img src="" alt="" /> 
(ii) Which acid has the larger Ka?

What will be the color of the indicator in the above question in a solution that has a pH of 6?

Acid Base Titration

Consider the titration of 100.0 mL of 0.016 M H2SO4 with 0.400 M NaOH at the equivalence point

The pH of this buffer would be lower than that desired.

Correct, the effective buffer range is within &#177;1 pH unit of the pKa.

The pH of this buffer would be higher than that desired.

None of the acids would buffer at pH 5.00.

This is one acid that would buffer at the given pH.

Use the pKa to determine the effective buffer range.

Which of the following acids would be needed to combine with its potassium salt to produce a solution buffered at pH 5.00? Chlorous acid: pKa = 1.95 Nitrous acid: pKa = 3.34 Formic acid: pKa = 3.74 Acetic acid: pKa = 4.74 Hypochlorous acid: pKa = 7.54

If at the equivalence point, the moles of acid equal the moles of base and moles&#160;equal molarity multiplied by liters&#160;then at the equivalence point we can use the formula:&#160;

A 4.36-g sample of an unknown alkali metal hydroxide is dissolved 
in 100.0 mL of water. An acid–base indicator is added, 
and the resulting solution is titrated with 2.50 M HCl(aq) 
solution. The indicator changes color, signaling that the 
equivalence point has been reached, after 17.0 mL of the hydrochloric 
acid solution has been added. (b) What is the identity of 
the alkali metal cation: Li+, Na+, K+, Rb+, or Cs+?

When dealing with the equivalence point make sure you correctly calculate the molarity for both the acid and base.&#160;

Consider the titration of a 20.0-mL sample of 0.105 M HC2H3O2 
with 0.125 M NaOH. Determine each quantity. 
b. the volume of added base required to reach the equivalence 
point

A 5.55-g sample of a weak acid with Ka = 1.3 * 10 - 4 was combined 
with 5.00 mL of 6.00 M NaOH, and the resulting solution 
was diluted to 750.0 mL. The measured pH of the solution was 
4.25. What is the molar mass of the weak acid?

A 25.00-mL sample of an unknown HClO4 solution requires titration
with 22.62 mL of 0.2000 M NaOH to reach the equivalence
point. What is the concentration of the unknown HClO4
solution? The neutralization reaction is
HClO4(aq) + NaOH(aq)¡H2O(l ) + NaClO4(aq)

Which of the following mixtures has the higher pH? 
(a) Equal volumes of 0.10 M HCN and 0.10 M NaOH 
(b) Equal volumes of 0.10 M HClO4 and 0.10 M NaOH

(a) A 0.1044-g sample of an unknown monoprotic acid requires 
22.10 mL of 0.0500 M NaOH to reach the end point. 
What is the molar mass of the unknown?

In analytical chemistry, bases used for titrations must often be 
standardized; that is, their concentration must be precisely determined. 
Standardization of sodium hydroxide solutions can 
be accomplished by titrating potassium hydrogen phthalate 
(KHC8H4O4), also known as KHP, with the NaOH solution to be 
standardized. 
b. The titration of 0.5527 g of KHP required 25.87 mL of an 
NaOH solution to reach the equivalence point. What is the 
concentration of the NaOH solution?

A 1.248-g sample of limestone rock is pulverized and then 
treated with 30.00 mL of 1.035 M HCl solution. The excess 
acid then requires 11.56 mL of 1.010 M NaOH for neutralization. 
Calculate the percentage by mass of calcium carbonate 
in the rock, assuming that it is the only substance reacting 
with the HCl solution.

Acid Base Titration Curves

Is the pH greater than, equal to, or less than 7 after the neutralization of each of the following pairs of acids and bases?
(c) HBr and aniline (C6H5NH2)

A 40.0 mL sample of a mixture of HCl and H3PO4 was titrated with 0.100 M NaOH. The first equivalence point was reached after 88.0 mL of base, and the second equiva-lence point was reached after 126.4 mL of base. 
(c) What percent of the HCl is neutralized at the first equivalence point?

The graphs labeled (a) and (b) show the titration curves for two 
equal-volume samples of bases, one weak and one strong. Both 
titrations were carried out with the same concentration of 
strong acid. 
a.  
b.  
(ii) Which graph corresponds to the titration of the strong 
base and which one to the weak base?

Label Titration Curves

Determine whether each of the following statements concerning 
the titrations in Problem 17.35 is true or false. 
(b) The titration curves will both be essentially the same 
after passing the equivalence point.<img src="https://lightcat-files.s3.amazonaws.com/problem_images/f9ecdeb1c62e5d36-1667317176391.jpg" alt="" />

The strong acid HA is mixed with an equal molar amount of aqueous NaOH. Which of the following pictures represents the equilibrium state of the solution? (Na+ ions and solvent water molecules have been omitted for clarity.)
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/cda5719065d9adfc-1673032410904.jpg" alt="" /> 
(1) <img src="" alt="" />
(2) <img src="" alt="" />
(3) <img src="" alt="" />
(4) <img src="" alt="" />

 The acid form of an indicator is red and its anion is blue

The following plot shows two pH titration curves, each representing the titration of 50.0 mL of 0.100 M acid with 0.100 M NaOH:
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/180c2ffac6f715a5-1672963290135.jpg" alt="" />.
(a) Which of the two curves represents the titration of a strong acid? Which represents a weak acid?

A 4.36-g sample of an unknown alkali metal hydroxide is dissolved
in 100.0 mL of water. An acid–base indicator is added,
and the resulting solution is titrated with 2.50 M HCl(aq)
solution. The indicator changes color, signaling that the
equivalence point has been reached, after 17.0 mL of the hydrochloric
acid solution has been added. (a) What is the molar
mass of the metal hydroxide?

Depending on the types of acids and bases mixing, at&#160;the equivalence point, the pH can be less than, greater than or equal to 7.&#160;

Consider the titration of 40.0 mL of 0.0800 M HCl with 0.0160 M Ca(NH2)2.a) How many milliliters of 0.0160 M Ca(NH2)2 are required to reach the equivalence point

The following plot shows two pH titration curves, each representing the titration of 50.0 mL of 0.100 M acid with 0.100 M NaOH:
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/180c2ffac6f715a5-1672963290135.jpg" alt="" />.
(c) What is the approximate pKa of the weak acid?

Consider the curve shown here for the titration of a weak base 
with a strong acid and answer each question.
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/1d750d5cd28eda86-1661444678891.jpg" alt="" />
a. What is the pH and what is the volume of added acid at the 
equivalence point?

The equivalence point was reached in titrations of three unknown bases at pH 5.53 (base A), 4.11 (base B), and 6.00 (base C). 
(a) Which is the strongest base?
(b) Which is the weakest base?

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[BOOK CHEM] Clutch Version

Weak Acid Strong Base Titrations

Whenever a WEAK ACID reacts with a STRONG BASE we use an ICF Chart to determine the pH of the solution.&#160;

Strong Acid Strong Base Titrations

In a Strong Acid-Strong Base Titration we do not use an ICF Chart or ICE Chart to determine the pH of the solution.&nbsp;

Titrations of Diprotic and Polyprotic Acids

A diprotic or polyprotic buffer can be approached in a way similar to monoprotic buffers. The key difference is that multiple pKa values will be involved.&#160;

Buffer

Weak Base Strong Acid Titrations

Whenever a&nbsp;WEAK BASE reacts with a&nbsp;STRONG ACID we use an&nbsp;ICF Chart to determine the pH of the solution.&nbsp;