Chemistry – Chemical reactions - Physical and chemical changes | e-Consult
Chemical reactions - Physical and chemical changes (1 questions)
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The balanced chemical equation for the reaction between hydrochloric acid and sodium hydroxide is:
| HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l) |
Two observable signs that a chemical reaction has taken place are:
- Formation of a gas: The reaction produces hydrogen gas (H2), which is a colourless, flammable gas. You would see bubbles forming.
- Change of colour: The solution may change colour. For example, the hydrochloric acid is typically a clear solution, and the sodium hydroxide is also clear. The resulting solution (sodium chloride solution) is clear.