2 marksShort AnswerSection A

Write the name and the structural formula of the compound formed when ethanol is heated at 443 K with excess of conc. $H_2SO_4$ . State the role of conc. $H_2SO_4$ in this reaction. Write chemical equation for the reaction.

Carbon and its Compounds

Chemical Properties of Carbon Compounds

Official Answer

When ethanol is heated at $443\text{ K}$ with excess of concentrated sulphuric acid ( $\text{H}_2\text{SO}_4$ ), it undergoes dehydration to form ethene.

1. Name of the Compound

Ethene

2. Structural Formula of Ethene

$\begin{array}{cc} \text{H} & \text{H} \\ | & | \\ \text{C} = & \text{C} \\ | & | \\ \text{H} & \text{H} \end{array}$

3. Role of Concentrated $\text{H}_2\text{SO}_4$

Concentrated sulphuric acid acts as a dehydrating agent in this reaction, as it removes a water molecule from the ethanol molecule.

4. Chemical Equation

$\text{CH}_3\text{CH}_2\text{OH} \xrightarrow{\text{Hot conc. } \text{H}_2\text{SO}_4, 443\text{ K}} \text{CH}_2=\text{CH}_2 + \text{H}_2\text{O}$

EtheneDehydrating agentDehydrationCH2=CH2443 K

Marking Scheme

10.5 marks
20.5 marks
30.5 marks
40.5 marks

Hint

Think about what happens when water is removed from an alcohol. An alkene is formed. Concentrated sulphuric acid is a well-known agent that removes water.

Quick Oral Answer

When ethanol is heated with concentrated sulphuric acid at 443 K, it dehydrates to form ethene gas. The concentrated acid acts as a dehydrating agent.

Analysis & Explanation

Heating ethanol at $443\text{ K}$ with excess concentrated sulphuric acid results in the elimination of a water molecule (dehydration). The hydroxyl group ( $-\text{OH}$ ) from one carbon atom and a hydrogen atom ( $-\text{H}$ ) from the adjacent carbon atom are eliminated as water, establishing a double bond between the two carbon atoms to form an unsaturated hydrocarbon, ethene. Concentrated $\text{H}_2\text{SO}_4$ has a strong affinity for water, making it an excellent dehydrating agent for this reaction.

Common Mistakes

1Writing the product as ethane instead of ethene.
2Forgetting to mention the temperature condition (443 K), which is crucial because at lower temperatures (like 413 K), ether is formed instead.
3Not specifying that conc. H2SO4 acts as a dehydrating agent.

Interesting Facts

Ethene is a plant hormone that plays a key role in the natural ripening of fruits.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2013?

This question carries 2 marks in the CBSE Class 10 Science 2013 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 2013 paper?

This is a Short Answer question from Section A in the CBSE Class 10 Science 2013 paper.