Concept explainers
Interpretation:
Why the setup for
Concept Introduction:
There are associated scales within the chemistry utilized to find out how basic and acidic a solution is, as well as the strength of bases and acids. Though most familiar is pH scale, Ka, pKa, Kb and pKb are the common calculation which offer understanding into acid-base reactions.
Answer to Problem 8.91P
Scale of Kb values for bases is unnecessary because the strength of two bases can be compared from the strength of their conjugate acids.
Explanation of Solution
The acid ionization constant, Ka, is the equilibrium constant for acid’s ionization. For the ionization of an acid, say HA, in an aqueous solution we get.
The square brackets denote the concentration. The concentration of water is not considered as water is exist in excess.
The Ka equation displays that the greater the dissociation of acid, the greater the value of Ka.
If there is a stringer acid, it will dissociate to a greater extent. Therefore, the numerator within the equation of Ka is larger, and thus, Ka will have the greater value.
Therefore, the weak acid’s strength is expressed in terms of Ka.
As per the Bronsted-Lowry concept of bases and acids, an acid is known as the proton donor, and a base is the proton acceptor.
When an acid donates a proton to another ion or molecule, it is converted to the conjugate base. For illustration,
When a base accepts a proton, it is converted to the conjugate acid. For illustration.
As per the Bronsted-Lowry definitions any molecules or ions pairs which might be interconverted by the transfer of proton is known as conjugate acid-base pair. Therefore, CH3 COOH and CH3 COO- is a conjugate acid-base pair and NH3 andNH4 + is a conjugate acid-base pair.
There is an inverse relationship amid the strength of acid and its conjugate base. The stronger the acid, the weaker is the conjugate base. The acid ionization constant, Ka, expresses the weak acid’s strength.
The below table shows values of ka for weak acids:
Ka values of weak acids.
Formula | Name | Ka | |
H3 PO4 | Phosphoric acid | ||
HCOOH | Formic acid | ||
CH3 CH(OH)COOH | Lactic acid | ||
CH3 COOH | Acetic acid | ||
H2 CO3 | Carbonic acid | ||
H2 PO4 - | Dihydrogen phosphate ion | ||
H3 BO3 | Boric acid | ||
NH4 + | Ammonium ion | ||
HCN | Hydrocyanic acid | ||
C6 H5 OH | Phenol | ||
HCO3 - | Bicarbonate ion | ||
HPO42 - | Hydrogen phosphate ion |
If we want to compare the strength of two bases, we can compare the strength of their conjugate acids.
For illustration, let us compare the strength of two bases, phenoxide ion C6 H5 O- and bicarbonate ion HCO3-.
The conjugate acid of phenoxide ion i.e. C6 H5 O- is phenol C6 H5 OH.
Ka of phenol =
The conjugate acid of bicarbonate ion HCO3 - is carbonic acid H2 CO3.
Ka of carbonic acid =
Therefore, Ka of the carbonic acid is greater than Ka of phenol. Hence, the carbonic acid is stronger than phenol. The stronger the acid, the weaker is the conjugate base. Therefore, a phenoxide ion is stronger base than a bicarbonate ion.
Therefore, we could compare the strength of weak bases from the Ka scale of acids. Hence, a scale of Kb values for bases is unncessary.
Since, the strength of two bases can be compared from the strength of their conjugate acids thus, scale of Kb values for bases is unnecessary.
Want to see more full solutions like this?
Chapter 8 Solutions
Introduction to General, Organic and Biochemistry
- What is the expected order of decreasing acidity for the following molecules? HO OO I ||| > |V > | > || | > | > | > h || > | > ||| > |V || > | > IV > ||| * ) III > IV > `|| > | HO II HO CI III HO IV Clarrow_forward1) NaOEt 2) H3O+ =0arrow_forwardCompare columns I and II, and write A if the value in column lis greater than in II B if the value in column Il is greater than in I cif both values are equal D if the value in columnI cannot be compared with that in II Delocalization of Negative Charge Column I Column II NH Narrow_forward
- Which chemical specie is the base in the forward direction (left to right)?arrow_forward5. Complete the table: Chemical System 1. 1 М КСI 2. 1 M H2SO4 3.1 М КОН 4. 1 M HE 5. 1 M AI(OH)3 6. 1 М НСI 7.1 M table sugar Type of Substance | Intensity of Light Classification Typeofsubstance- ionic, strongacid, strong base, weak acid, weak base, organic which is neither an acid norbasearrow_forwardtex S Geometry w/DataX S Practice 10.10 | ScX S Geometry w/DateX G Sign in - Google/X Logins & Passwo X now.com/ilrn/takeAssignment/takeCovalentActivity.do?locator=assignment-take [Review Topics] [References] Use the References to access important values if needed for this question. Write a net ionic equation to show that hydroxylamine, NH₂OH, behaves as a Bronsted-Lowry base in water. BL base BL acid BL base BL acid + H₂O → Submit Answer Retry Entire Group 1 more group attempt remaining Next ... - ) + Previous + D 0 Other Bookmarks 8:36 PM 4/29/2022arrow_forward
- A bond between CO and M, where M is a lewis acid, which forms M-CO. Draw the lewis structures and resonace structures for M-CO. Where M does not have no lone pairs, has one lone pair and two lone pairs. Please be more detailed with the resonace and lewis structuresarrow_forwardPlease answer 6A and 6Barrow_forwardList the bond lenghts between the carbon and the oxygen atoms for the carboxylic acid and carboxylate ion and rank from shortest to longest. carboxylic acid carboxylate ion c-o c=o provide an explanation for the differences in the bond lengths and the orientation of the dipole moment between the acid and ion.arrow_forward
- LO-2 3. The measurement data for the dipole moment (µ) of two acid halide molecules expressed in Debye (D) units are HBr: 0.82 D and HI: 0.45 D. If the bond lengths of HBr and HI are 141 pm and 161 pm, respectively, calculate the partial charge (6) of each atom in the molecules. It is known that 1D=3.34x10- 30 Cm. How many significant figures are in your answer? Explain.arrow_forward4. A student has prepared 0.05 M solution of CH3-C=CH and has added to it 0.05 M solution of potassium tert-butoxide (K" O-C(CH3)3). (i) Write the equation for the acid-base reaction that might occur. (ii) With curved arrows track the movements of electron pairs. (iii) Assign Base, Acid, Conjugate acid for the base, Conjugate base for the acid. (iv) Calculate the percentage of deprotonated methyl acetylene taking into account that pKa of the conjugate acid of potassium tert-butoxide equals 18 and pKa of methyl acetylene equals 24.arrow_forwardPlease explain all the answer thoroughly so it makes sense. Please write legibly.arrow_forward
- Organic Chemistry: A Guided InquiryChemistryISBN:9780618974122Author:Andrei StraumanisPublisher:Cengage LearningChemistry: Matter and ChangeChemistryISBN:9780078746376Author:Dinah Zike, Laurel Dingrando, Nicholas Hainen, Cheryl WistromPublisher:Glencoe/McGraw-Hill School Pub Co