Question
\(C_6H_5COOH(aq)+NaOH(aq)→C_6H_5COONa(aq)+H2O(l)\)
Which of the following identifies a conjugate acid-base pair in the reaction represented above?
▶️Answer/Explanation
Ans: B
The conjugate base is the species that results from the loss of the proton \(H^+\) from the acid. In this reaction, \(C_6H_5COOH\) is a weak acid that donates an \(H^+\) to \(OH^−\) to form \(H_2O\) and the conjugate base, \(C_6H_5COO^−\).
Question
\(C_6H_5COOH(aq)+NaOH(aq)→C_6H_5COONa(aq)+H2O(l)\)
Which of the following identifies a conjugate acid-base pair in the reaction represented above?
▶️Answer/Explanation
Ans: B
The conjugate base is the species that results from the loss of the proton \(H^+\) from the acid. In this reaction, \(C_6H_5COOH\) is a weak acid that donates an \(H^+\) to \(OH^−\) to form \(H_2O\) and the conjugate base, \(C_6H_5COO^−\).
Question
In the reaction between \(C_5H_5N\)(aq) and HCl(aq) represented above, \(C_5H_5N\) acts as
A a Brønsted-Lowry base
B a Brønsted-Lowry acid
C the conjugate base of HCl
D the conjugate acid of \([C_5H_5NH]^+\)
▶️Answer/Explanation
Ans:A
\(C_5H_5N\) acts as a Brønsted-Lowry base, because it accepts a proton \(H^+\) from HCl.
Question
Based on the Brønsted-Lowry theory of acids and bases, which of the following species can act as both a conjugate acid and a conjugate base?
A \(HS^−\)
B \(CH3COO^−\)
C \(H_3O^+\)
D \(NH_4^+\)
▶️Answer/Explanation
Ans: A
\( HS^−\) can accept a proton to form H2S, its conjugate acid. Also, \(HS^−\) can donate a proton to form \(S_2^−\), its conjugate base.
Question
\(Cu(s)+4HNO_{3}(aq)\rightarrow Cu(NO_{3})(aq)+NO_{2}(g)+2H_{2}O(l)\)
Each student in a class placed a 2.00 g sample of a mixture of Cu and Al in a beaker and placed the beaker in a fume hood. The students slowly poured 15.0 mL of 15.8 M HNO3(aq) into their beakers. The reaction between the copper in the mixture and the HNO3(aq) is represented by the equation above. The students observed that a brown gas was released from the beakers and that the solutions turned blue, indicating the formation of Cu2+(aq). The solutions were then diluted with distilled water to known volumes.
Which of the following is true about the reaction?
(A) It is a Brønsted-Lowry acid-base reaction, because the solution is neutral at the end.
(B) It is a Brønsted-Lowry acid-base reaction, because\( HNO_{3}\)(aq) is a strong acid.
(C) It is a redox reaction, because Cu(s) is oxidized and\( H^{+}\)(aq) is reduced.
(D) It is a redox reaction, because Cu(s) is oxidized and the nitrogen atom in\( NO_{3}\)(aq) is reduced.
▶️Answer/Explanation
Ans:C