Q21
2 marksVery Short AnswerSection B

When magnesium ribbon is burnt in air, an ash of white colour is produced. Write chemical equation for the reaction giving the chemical name of the ash produced. State the type of chemical reaction giving justification for your answer.

Chemical Reactions and Equations
Combination Reaction
Official Answer

When a magnesium ribbon is burnt in air, it reacts with oxygen to produce a white ash of magnesium oxide.


1. Chemical Equation

2Mg(s)+O2(g)2MgO(s)2Mg(s) + O_2(g) \rightarrow 2MgO(s)


2. Chemical Name of the Ash

Magnesium oxide


3. Type of Chemical Reaction

Combination Reaction (It is also an oxidation and an exothermic reaction).


4. Justification

A combination reaction is defined as a reaction in which a single product is formed from two or more reactants. Here, two reactants—magnesium (MgMg) and oxygen (O2O_2)—combine to form a single product, magnesium oxide (MgOMgO).

Magnesium oxide2Mg(s) + O2(g) -> 2MgO(s)Combination reactionSingle product

Marking Scheme

  • 11 mark
  • 20.5 marks
  • 30.5 marks

Hint

Identify the reactants involved when burning in air (magnesium and oxygen) and write their balanced equation. A reaction where multiple reactants form a single product is a combination reaction.

Quick Oral Answer

Magnesium ribbon is rubbed with sandpaper before burning to remove the protective layer of basic magnesium carbonate that forms on its surface due to reaction with moist air.

Common Mistakes

  1. 1Writing an unbalanced skeletal equation: Mg+O2MgOMg + O_2 \rightarrow MgO.
  2. 2Writing the incorrect chemical formula for magnesium oxide as MgO2MgO_2 instead of MgOMgO.
  3. 3Forgetting to mention that oxygen from the air is the second reactant.

Interesting Facts

Magnesium burns with an extremely bright, dazzling white flame that can damage eyes if stared at directly; this is why safety glasses are recommended.

Historically, magnesium powder was used as a flash source in early photography.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2024?

This question carries 2 marks in the CBSE Class 10 Science 2024 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Chemical Reactions and Equations" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Combination Reaction" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2024 paper?

This is a Very Short Answer question from Section B in the CBSE Class 10 Science 2024 paper.