Nimo

Study smarter with Nimo

Personalised revision that adapts to you. Ace your revision with unlimited practice questions that are designed to help you learn faster. We're slowly rolling out to more and more students.

Try Nimo

Metal hydroxide tests and writing balanced equations

Chemical analysis • Identification of ions

Key concepts

What you'll likely be quizzed about

  • Adding hydroxide ions (often as NaOH) to a solution of metal ions causes formation of a metal hydroxide if that hydroxide is insoluble.
  • Precipitation occurs when the ionic product exceeds the solubility product, resulting in a visible solid from the ionic mixture.
  • The ionic equation representation clarifies the reacting ions and the precipitate species.

Flashcards

Test your knowledge with interactive flashcards

Write a full equation for FeCl3 reacting with NaOH to form the hydroxide.

Click to reveal answer

FeCl3(aq) + 3NaOH(aq) → Fe(OH)3(s) + 3NaCl(aq).

Key notes

Important points to keep in mind

Add sodium hydroxide dropwise and observe precipitate colour immediately.

Test with excess NaOH to detect amphoteric hydroxides (Al3+, Zn2+ dissolve).

Warm the mixture to test for ammonium ions; look for ammonia gas and litmus change.

Write ionic equations to show only species that change during precipitation.

Use full equations with spectator ions to demonstrate mass and charge balance.

Consider oxidation: Fe2+ precipitates darken on exposure to air, indicating Fe3+ formation.

Low concentrations or colored solutions can mask weak white precipitates.

Carbonate contamination produces additional precipitates and interferes with interpretation.

Differentiate white precipitates (Al3+, Ca2+, Mg2+) by testing solubility in excess NaOH and using further tests.

State symbols clarify equations: (aq) for dissolved ions, (s) for precipitates, (g) for ammonia.

Built with v0