Question 1

Each time the pH of a solution goes up one pH unit, the concentration of H₃O⁺ ions goes ____ by a factor of ______. A) up, 10 B) down, 10 C) down, 100

Accepted Answer

The pH scale is logarithmic, meaning each whole number increase in pH represents a tenfold decrease in the concentration of hydrogen ions (H+). Therefore, if the pH goes up by one unit, the concentration of H+ ions goes down by a factor of 10.

Question 2

Find a correct statement: A) If HA is a strong acid, then A^- is its weak conjugate base. B) If HA is a strong acid, then A^- is its strong conjugate base. C) If HA is a weak acid, then A^- is its weak conjugate base.

Accepted Answer

A strong acid has a weak conjugate base because the acid donates its proton easily, leaving the conjugate base with little tendency to accept a proton.

Question 3

Which of the following statement(s) is/are correct?
(i) HClO₄ is an example of an oxoacid.
(ii) H₃PO₄ is a diprotic acid.
(iii) Distribution diagrams relate pH with pK_a of a polyprotic acid.

A) Only statement (i)
B) Statements (i) and (iii)
C) Statements (ii) and (iii).

Accepted Answer

A

Question 4

Find the weakest aqua acid among these three: [Fe(H₂O)₆]³⁺, [Zn(H₂O)₆]²⁺ and [Mg(H₂O)₆]²⁺ A) [Fe(H₂O)₆]³⁺ B) [Zn(H₂O)₆]²⁺ C) [Mg(H₂O)₆]²⁺

Accepted Answer

The acidity of aqua complexes is influenced by the charge density of the central metal ion. Magnesium (Mg) has a lower charge density compared to Iron (Fe) and Zinc (Zn) due to its larger size and same charge, making its aqua complex the weakest acid among the given options.

Question 5

If you replace one -OH group in H₂SO₄ with -CCl₃, A) the resulting acid, H(CCl₃)SO₃ is weaker than H₂SO₄. B) the resulting acid, H(CCl₃)SO₃ is stronger than H₂SO₄ C) we cannot say anything about the acidity of the new compound relative to H₂SO₄.

Accepted Answer

Replacing an -OH group with a -CCl3 group in an acid increases the acid's strength due to the electron-withdrawing effect of the -CCl3 group, which stabilizes the conjugate base.

Question 6

&#34;An adduct or complex is formed from a Lewis acid as an electron pair donor and Lewis base as an electron pair acceptor.&#34; This statement is&#10;A) incorrect: the definition of Lewis acids and bases is inversed.&#10;B) correct as is.&#10;C) incorrect: acid-base reactions are neutralization reactions.

Accepted Answer

In Lewis theory, a Lewis acid is an electron pair acceptor, and a Lewis base is an electron pair donor. The statement has the definitions reversed.

Question 7

Which of the following compounds can act as Lewis acids: (i) SO₂ (ii) SnCl₃^- (iii) B(OH)₃ and (iv) CF₄ A) (i) and (ii). B) (i) and (iii). C) (ii), (iii) and (iv).

Accepted Answer

SO₂ and B(OH)₃ can act as Lewis acids because they can accept electron pairs. SO₂ can accept electrons due to the presence of an empty d-orbital, and B(OH)₃ can accept electrons due to the electron deficiency of boron.

Question 8

Which of the following general reactions illustrates displacement reaction?&#10;A) A-B &#8594; A + :B.&#10;B) A-B + A'-B' &#8594; A-B' + A'-B.&#10;C) A-B + B' &#8594; A-B' + B.

Accepted Answer

In a displacement reaction, one element replaces another in a compound, forming a new compound and releasing a different element. Choice C illustrates this, where B' displaces B in the compound A-B, forming a new compound A-B' and releasing B.

Question 9

Find the correct statement:&#10;A) Hard cations with high charge and small radius form stable compounds with hard anions.&#10;B) Hard anions are formed by elements found at the bottom right of the periodic table.&#10;C) Soft cations have closed shell electronic configuration.

Accepted Answer

Hard cations, which have a high charge and small radius, tend to form stable compounds with hard anions due to their similar properties, such as high electronegativity and small size, which lead to strong ionic or covalent bonding.

Question 10

Consider a solvent AB that undergoes autoionization to produce AB₂^- and A⁺ ions. Then the correct definition of acids and bases in this solvent would be: A) An acid would increase the concentration of A⁺ while a base would increase the concentration of AB₂^-. B) An acid would increase the concentration of AB₂^- while a base would increase the concentration of A⁺. C) The definition cannot be provided without knowing the exact nature of A and B.

Accepted Answer

In this solvent system, an acid is defined as a substance that increases the concentration of the cation (A⁺), while a base increases the concentration of the anion (AB₂^-).

Deck 5: Acids and Bases