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
- phosphate rock, an ore found in extensive deposits 11-36. A common natural source of phosphorus is 11-21. The chemical 2-propanone, commonly known yocean floor. The formula 6 H,PO, (1) + 10 CaSO,(s) + 2 H,O(1) of one type of phosphate rock is Ca1o(OH),(PO,J Phosphate rock is converted to phosphoric acid by as acetone, is an important chemical solvent; a famil- iar home use is as a nail polish remover. Chemical analysis shows that acetone is 62.0% carbon, 10.4% hydrogen, and 27.5% oxygen by mass. Determine the empirical formula of acetone. In a separate experi- ment, the molecular mass is found to be 58.1. What is the molecular formula of acetone? in areas that were originally the reaction described by the equation Cao (OH),(PO,)6(s) + 10 H„SO,(1) →arrow_forward1a. 1b. 1c.arrow_forwardRank the following protons in order of increasing acidity. ||| = ||| Drag and drop options into correct order and submit. For keyboard navigation... SHOW ||| = ||| 2 4 5 = 1 Н PHOTO 3 = 3 1 2 -H н 5 нarrow_forward
- Give correct detailed Solution with explanation needed. Don't use Ai for answering this..don't give Handwritten answerarrow_forwardUse bond dissociation enthalpies to calculate values of delta H° for the following reactions a) CH3-CH3 + I2 = CH3CH2I + HI b) CH3CH2Cl + HI = CH3CH2I + HClarrow_forwardA 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_forward
- Use the molecular orbital theory to explain the fundamentals of acid-base interactions (frontier molecular orbitals, HOMO-LUMO combinations)arrow_forward6-16 The difference between melting point and boiling point (° C) is given below for each of the Group IIB halides. F CI Br Zn 630 640 5. 405 390 25 355 300 80 285 405 Hg2 100 What deductions can you draw?arrow_forward4. a) A polyatomic ion of formula SCN is called thiocyanate. Draw a Lewis structure for thiocyanate anion based on the total number of valence shell electrons and a connectivity S-C-N. Show your work b) Next, apply the concept of resonance to arrive at a second resonance form for the ion with formal charge on a different atom. Circle the 2 elements that are Lewis basic in this polyatomic ion. c) Based on your answers above, state which intermolecular attractive forces are important in SCN".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