Question 1

Which of the following best describes a Brønsted-Lowry acid?

Accepted Answer

A substance that donates a proton ($$H^+) to $$another species.

Question 2

Given the following reaction: $$CH_3COOH + H_2O \rightarrow CH_3COO^- + H_3O^+$$, which species is the conjugate base?

Accepted Answer

$$CH_3COO^-$$

Question 3

Which of the following statements about pKa is correct?

Accepted Answer

A lower pKa value indicates a stronger acid.

Question 4

Which of the following curved arrow notations correctly represents the movement of electrons in a proton transfer from $$NH_3 to$$ $$H_2O$$?

Accepted Answer

Arrow from $$NH_3$$ lone pair to $$H of$$ $$H_2O.$$

Question 5

Which factor does NOT affect the stability of a conjugate base according to ARIO?

Accepted Answer

Molecular weight of the acid.

Question 6

A student is comparing the acidity of $$CH_3OH$$ and $$CH_3SH. $$Using ARIO, which is the stronger acid and why?

Accepted Answer

$$CH_3OH is $$stronger because oxygen is more electronegative than sulfur.

Question 7

Which solvent effect would most likely increase the acidity of a compound?

Accepted Answer

Using a polar protic solvent that stabilizes the conjugate base.

Question 8

Which of the following acids has the lowest pKa value?

Accepted Answer

$$HCl$$ ($$pKa \approx -7)$$

Question 9

Which statement best explains why resonance increases the stability of a conjugate base?

Accepted Answer

Resonance allows the negative charge to be delocalized over multiple atoms.

Question 10

A solution contains both $$HCO_3$$^-$$ and H_2CO_3$. Which acts as the conjugate base in this system?

Accepted Answer

$$HCO_3$$^-$$

Question 11

Which of the following is the correct relationship between acid strength and conjugate base strength?

Accepted Answer

Weak acids have strong conjugate bases.

Question 12

If the equilibrium constant $$K_{eq}$$ for the reaction $$HA + H_2O \rightleftharpoons A^- + H_3O^+ is $$much greater than 1, what does this indicate about the acid $$HA$$?

Accepted Answer

$$HA is a $$strong acid.

Question 13

Which of the following is NOT a Lewis acid?

Accepted Answer

$$NH_3$$

Question 14

A medical case involves a patient with metabolic acidosis. Which buffer system is most relevant in maintaining blood pH?

Accepted Answer

Bicarbonate buffer system ($$HCO_3^-/H_2CO_3$)

Question 15

Which of the following best describes the role of inductive effects in acid strength?

Accepted Answer

Electron-withdrawing groups increase acid strength by stabilizing the conjugate base.

Question 16

Which acid is stronger: $$HF or$$ $$HCl$$? Use periodic trends and ARIO to justify your answer.

Accepted Answer

$$HCl is $$stronger because chlorine is larger and can better stabilize the negative charge.

Question 17

Which of the following is the correct curved arrow notation for the acid-base reaction between $$CH_3COOH$$ and $$OH^-$$?

Accepted Answer

Arrow from $$OH^-$$ lone pair to acidic $$H of$$ $$CH_3COOH.$$

Question 18

A student claims that $$NH_4$$^+$$ is a Lewis base. Is this correct? Why or why not?

Accepted Answer

No, $$NH_4$$^+$$ cannot donate an electron pair.

Question 19

Which of the following is the correct order of acid strength for the following compounds: $$H_2O$$, $$H_2S$$, $$H_2Se$$?

Accepted Answer

$$H_2O \u003c H_2S \u003c H_2Se$$

Organic Chemistry Topic 3

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