When substance X is dissolved in water, the only positive ions in the solution are hydrogen ions. Substance X could be which of the following?

When substance X is dissolved in water, the only positive ions in the solution are hydrogen ions. Substance X could be which of the following?

• A. NH3
• B. NaH
• C. NaOH
• D. H2S

Answer: (D)

When a substance dissolves in water, the positive ions present come from species that release protons to the solution, forming hydronium ions (H3O+). If the only positive ions are hydrogen, the solute must be an acid that donates protons without introducing any other cations (like metal ions or ammonium). Hydrogen sulfide acts as a weak acid in water, dissociating to form H3O+ and HS−. This means the positive ions in the solution are solely hydrogen ions, with no other cations present. The other options introduce other positive ions: ammonia forms NH4+ in water, a metal hydride would yield Na+ plus a basic environment, and sodium hydroxide provides Na+ and OH−. So hydrogen sulfide is the one that matches the condition.

When a substance dissolves in water, the positive ions present come from species that release protons to the solution, forming hydronium ions (H3O+). If the only positive ions are hydrogen, the solute must be an acid that donates protons without introducing any other cations (like metal ions or ammonium).

Hydrogen sulfide acts as a weak acid in water, dissociating to form H3O+ and HS−. This means the positive ions in the solution are solely hydrogen ions, with no other cations present. The other options introduce other positive ions: ammonia forms NH4+ in water, a metal hydride would yield Na+ plus a basic environment, and sodium hydroxide provides Na+ and OH−. So hydrogen sulfide is the one that matches the condition.