Chemistry 5070 · O Level · Identification of ions and gases

Identification of ions and gases — practice question

Separate tests are carried out on two samples of a colourless solution using aqueous sodium hydroxide, $\text{NaOH(aq)}$, and aqueous ammonia, $\text{NH}_3\text{(aq)}$, and the observations are noted. • A white precipitate appears when two drops of $\text{NaOH(aq)}$ are added. In excess $\text{NaOH(aq)}$, this precipitate dissolves. • A white precipitate appears when two drops of $\text{NH}_3\text{(aq)}$ are added. In excess $\text{NH}_3\text{(aq)}$, this precipitate dissolves. What conclusion can be drawn from these observations?

  • AThe anion present is $\text{Cl}^-$.
  • BThe anion present is not $\text{Cl}^-$.
  • CThe cation present is $\text{Al}^{3+}$.
  • DThe cation present is $\text{Zn}^{2+}$.

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