A student adds hydrochloric acid to sodium hydrogen carbonate. Which observation confirms neutralization?
Effervescence
Hydrochloric acid (HCl) is an acid and sodium hydrogen carbonate (NaHCO3) is a mild base. When they meet they react as HCl + NaHCO3 → NaCl + H2O + CO2, and the carbon dioxide gas that is released escapes as bubbles, which is seen as effervescence.
Neutralisation of an acid and a base is exothermic, so the temperature usually rises slightly — it does not drop. NaCl is highly soluble in water, so no precipitate forms. Colour change to red would need an acid-base indicator like methyl orange or litmus, which is not being used here. Therefore, the visible bubbling of CO2 is the observation that confirms the reaction.
Hence, the answer is Effervescence.
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Important Questions from Chemical Reaction
Which of the following statement is/are true?
I. In physical change new substance is formed. substance is formed.
II. In chemical change no new substance is formed.
Which of the following cells involves similar chemical reactions?
The information not obtained from balanced chemical equation is
Oxygen cannot be obtained by which one of the following methods?
Which of the following compound is responsible for tarnishing of silver?
