Which of the following lists the significant chemical species present in a solution of aqueous ammonia (NH_3 in water)?

• A. NH_3, H_2O, Na^+, OH^-
• B. NH_3, NH_4^+, H_3O^+
• C. NH_3, H_2O, NH_4^+, OH^-
• D. NH_3, NH_4^+, Cl^-

Answer: (C)

Verified step by step guidance

1. Step 1: Understand that aqueous ammonia (NH_3 in water) is a weak base that partially reacts with water to establish an equilibrium between ammonia, water, ammonium ions, and hydroxide ions.
2. Step 2: Write the chemical equilibrium reaction for ammonia in water: \(\mathrm{NH_3 + H_2O \rightleftharpoons NH_4^+ + OH^-}\).
3. Step 3: Identify the species present in the solution: unreacted ammonia (\(\mathrm{NH_3}\)), water (\(\mathrm{H_2O}\)), ammonium ion (\(\mathrm{NH_4^+}\)), and hydroxide ion (\(\mathrm{OH^-}\)).
4. Step 4: Recognize that ions like \(\mathrm{Na^+}\) or \(\mathrm{Cl^-}\) are not present unless a salt containing these ions is added, so they are not part of the species in pure aqueous ammonia.
5. Step 5: Conclude that the significant chemical species in aqueous ammonia are \(\mathrm{NH_3}\), \(\mathrm{H_2O}\), \(\mathrm{NH_4^+}\), and \(\mathrm{OH^-}\).