On dropping a small piece of sodium in a test tube containing carbon compound ‘X’ with molecular formula , a brisk effervescence is observed and a gas ‘Y’ is produced. On bringing a burning splinter at the mouth of the test tube the gas evolved burns with a pop sound. Identify ‘X’ and ‘Y’. Also write the chemical equation for the reaction. Write the name and structure of the product formed, when you heat ‘X’ with excess conc. sulphuric acid.
On dropping a small piece of sodium in a test tube containing carbon compound ‘X’ with molecular formula , a brisk effervescence is observed and a gas ‘Y’ is produced. On bringing a burning splinter at the mouth of the test tube the gas evolved burns with a pop sound. Identify ‘X’ and ‘Y’. Also write the chemical equation for the reaction. Write the name and structure of the product formed, when you heat ‘X’ with excess conc. sulphuric acid.
- Identification of X and Y:
- Compound X is ethanol ( or ).
- Gas Y is hydrogen gas ().
- Chemical Equation for the reaction of X with sodium:
(The ionic product formed is sodium ethoxide)
- Reaction of X with excess concentrated sulphuric acid:
When ethanol (X) is heated with excess concentrated at , it undergoes dehydration to form ethene.
- Name of the product: Ethene
- Structure of the product:
``
H H
\ /
C = C
/ \
H H
``
- Chemical Equation:
Marking Scheme
- 1Identification of X as ethanol and Y as hydrogen gas (1 mark)
- 2Balanced chemical equation for the reaction of ethanol with sodium (1 mark)
- 3Name (ethene) and correct structural formula of the dehydration product (1 mark)
Hint
Compound X is a two-carbon alcohol that reacts with sodium to release a gas that burns with a pop sound. Heating this alcohol with a strong dehydrating agent like conc. removes water to form an alkene.
Quick Oral Answer
Compound X is ethanol and gas Y is hydrogen. When ethanol is heated with excess concentrated sulphuric acid, it gets dehydrated to form ethene, which contains a double bond.
Analysis & Explanation
Ethanol reacts with active metals like sodium to form sodium ethoxide and hydrogen gas. Concentrated sulphuric acid acts as a strong dehydrating agent at high temperatures (), removing the group from one carbon and a hydrogen atom from the adjacent carbon to establish a carbon-carbon double bond, yielding ethene.
Common Mistakes
- 1Writing the formula of the gas as instead of .
- 2Confusing the dehydration product with ethane () instead of ethene ().
- 3Not mentioning the reaction conditions like heating with concentrated .
Interesting Facts
Concentrated sulphuric acid is so hungry for water (hygroscopic) that it can chemically strip hydrogen and oxygen atoms from organic molecules to form water, leaving behind carbon or unsaturated compounds.
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Frequently Asked Questions
How many marks does this question carry in CBSE Class 10 Science 2016?
This question carries 3 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" from CBSE Class 10 Science.
What type of question is this in the CBSE Class 10 Science 2016 paper?
This is a Short Answer question from Section A in the CBSE Class 10 Science 2016 paper.