A student adds a spoon full of powdered sodium hydrogen carbonate to a flask containing ethanoic acid. List two main observations, he must note in his note book, about the reaction that takes place. Also write chemical equation for the reaction.

Q: A student adds a spoon full of powdered sodium hydrogen carbonate to a flask containing ethanoic acid. List two main observations, he must note in his note book, about the reaction that takes place. Also write chemical equation for the reaction.

The two main observations that the student must note are: 1. **Brisk effervescence** is observed due to the rapid evolution of a colorless and odorless gas. 2. The evolved gas, when passed through lime water, **turns the lime water milky** (confirming the gas is carbon dioxide, $CO_2$). **Chemical Equation:** $$CH_3COOH + NaHCO_3 \rightarrow CH_3COONa + H_2O + CO_2$$

Also asked in:2016

Carbon and its Compounds

Chemical properties of Carbon Compounds - Ethanoic Acid

Official Answer

The two main observations that the student must note are:

Brisk effervescence is observed due to the rapid evolution of a colorless and odorless gas.
The evolved gas, when passed through lime water, turns the lime water milky (confirming the gas is carbon dioxide, $CO_2$ ).

Chemical Equation:

$CH_3COOH + NaHCO_3 \rightarrow CH_3COONa + H_2O + CO_2$

Brisk effervescenceColorless and odorless gasTurns lime water milkyCH3COOHNaHCO3CH3COONaCO2

Marking Scheme

11 mark for listing two correct observations (0.5 mark for brisk effervescence/evolution of gas, 0.5 mark for turning lime water milky).
21 mark for writing the correct balanced chemical equation with proper formulas of reactants and products.

Hint

Recall what gas is produced when an organic acid reacts with a metal hydrogen carbonate, and think about the characteristic test for that gas.

Quick Oral Answer

When ethanoic acid reacts with sodium hydrogen carbonate, it produces sodium acetate, water, and carbon dioxide gas. The main observations are brisk effervescence due to the evolution of carbon dioxide gas, which turns lime water milky.

Analysis & Explanation

When ethanoic acid ( $CH_3COOH$ ) reacts with sodium hydrogen carbonate ( $NaHCO_3$ ), it undergoes an acid-base reaction to form a salt (sodium acetate), water, and carbon dioxide gas.

Observation of Effervescence: The rapid generation of carbon dioxide ( $CO_2$ ) gas bubbles in the liquid mixture is seen as vigorous bubbling or brisk effervescence.
Lime Water Test: Carbon dioxide is a colorless, odorless gas. When passed through lime water (calcium hydroxide solution, $Ca(OH)_2$ ), it reacts to form an insoluble white precipitate of calcium carbonate ( $CaCO_3$ ), which turns the solution milky:

$Ca(OH)_2 + CO_2 \rightarrow CaCO_3 + H_2O$

Chemical Equation: The reaction is represented as:

$CH_3COOH(aq) + NaHCO_3(s) \rightarrow CH_3COONa(aq) + H_2O(l) + CO_2(g)$

Common Mistakes

1Writing the formula of sodium acetate incorrectly as $CH_3COONa_2$ or $NaCH_3COO$ .
2Forgetting to mention 'brisk' effervescence and simply writing 'gas is evolved'.
3Not mentioning the lime water test to confirm the identity of the evolved gas.

Interesting Facts

This reaction is the chemical basis behind the classic 'baking soda and vinegar volcano' demonstration, where the rapid release of carbon dioxide gas creates a dramatic foaming effect.

Ethanoic acid is the main component of vinegar, typically making up 5% to 8% of its volume.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2016?

This question carries 2 marks in the CBSE Class 10 Science 2016 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Carbon and its Compounds" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Chemical properties of Carbon Compounds - Ethanoic Acid" from CBSE Class 10 Science.

Has this question appeared in other CBSE Science papers?

Yes, a similar question appeared in the 2016 CBSE Class 10 Science paper.

What type of question is this in the CBSE Class 10 Science 2016 paper?

This is a Short Answer question from Section B in the CBSE Class 10 Science 2016 paper.