Question 1

Which of the following best explains why the addition of KC$$_8 to a 4f $$metal complex does NOT result in direct f-f bonding between the metals?

Accepted Answer

The added electrons preferentially occupy high-energy d orbitals rather than forming f-f bonds.

Question 2

Which of the following salts will produce an acidic solution when dissolved in water?

Accepted Answer

NH$$_4NO$_3$$

Question 3

Given the following reaction: 2Na$$_2$$CrO$$_4 + 2H$^+$$ $$\rightleftharpoons Na$_2Cr$_2O$_7 + H$_2O$$, what will happen to the color of the solution if HCl is added?

Accepted Answer

The solution will become more orange as the equilibrium shifts to form more dichromate.

Question 4

Which factor most increases the acidity of an oxyacid HXO$$_n as n $$increases?

Accepted Answer

The negative charge on the conjugate base is stabilized by additional oxygen atoms.

Question 5

Which of the following cations will most significantly lower the pH of an aqueous solution due to its high charge and small size?

Accepted Answer

Fe$$^{3+}$$

Question 6

A 0.22 M solution of NH$$_4Cl $$has a K$$_b$$ for NH$$_3 of$$ $$1.8 	imes 10$$^{-5}$$. What is the pH of the solution? (Use K_w = 1.0$$ 	imes $$10^{-14})$$

Accepted Answer

4.96

Question 7

Which of the following best describes the common ion effect?

Accepted Answer

The presence of a common ion suppresses the ionization of a weak electrolyte.

Question 8

Which of the following solutions will be basic?

Accepted Answer

Na$$_2CO$_3$$

Question 9

Arrange the following acids in order of increasing strength: HOI, HIO$$_2$$, HBrO$$_2$$, HClO$$_2$$, HClO$$_3.$$

Accepted Answer

HOI \u003c HIO$$_2$$ \u003c HBrO$$_2$$ \u003c HClO$$_2$$ \u003c HClO$$_3$$

Question 10

Which of the following best explains why carboxylic acids are stronger acids than alcohols?

Accepted Answer

The negative charge on the conjugate base is delocalized by resonance in carboxylates.

Question 11

If NaClO is added to a solution of HClO, what will happen to the pH and why?

Accepted Answer

The pH will increase because the common ion suppresses HClO ionization.

Question 12

Which of the following best describes why Fe$$^{3+} in $$water forms an acidic solution?

Accepted Answer

Fe$$^{3+}$$ polarizes the O–H bonds of bound water molecules, making H$$^+$$ easier to lose.

Question 13

A solution contains both NH$$_4^+$$ and ClO$$^-. $$Given $$K_b$$ for NH$$_3 is$$ $$1.8 	imes 10$$^{-5}$$ and K_a$ for HClO is 3.0$$ 	imes $$10^{-8}$$, will the solution be acidic or basic?

Accepted Answer

Basic, because ClO$$^- is a $$stronger base than NH$$_4^+ is an $$acid.

Question 14

Which of the following is NOT a factor that increases acid strength?

Accepted Answer

Increasing the strength of the H–A bond.

Question 15

Which of the following best describes the effect of adding NaOH to a solution of Na$$_2Cr$_2O$_7$$?

Accepted Answer

The equilibrium shifts to produce more chromate ions (yellow color).

Question 16

Which of the following statements about the 4f orbitals is correct?

Accepted Answer

4f orbitals are more contracted and less available for bonding compared to 5d or 6s orbitals.

Question 17

Which of the following best explains why the addition of a salt containing a common ion decreases the solubility of a sparingly soluble salt?

Accepted Answer

The increased concentration of the common ion shifts the dissolution equilibrium to the left.

Question 18

Which of the following is the correct expression for the acid dissociation constant ($$K_a) $$for the reaction NH$$_4^+ + H$_2O$$ $$\rightleftharpoons NH$_3 + H$_3O$^+$$?

Accepted Answer

$$K_a = \frac{[NH_3$][H_3O^+]}{[NH_4$^+]}$$

Acid-Base Properties of Salt Solutions, Molecular Structure and Acid Strength, and the Common Ion Effect

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