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Class 10
Chapter 3 Class 10 - Metals and Non-Metals (Term 1)

When a silvery grey powder of a solid (A) is  mixed with a powder of solid (B) no reaction  occurs. But if the mixture is ignited and lighted  using magnesium ribbon a reaction occurs with the evolution of a large amount of heat forming product  (C) which settles down as liquid metal and the  solid product (D) formed floats on the liquid (C).  (C) in solid form reacts with moisture to form rust.  The amount of heat generated during the reaction  is so high that the reaction is used in welding of  electric conductors, joints in railway tracks. Based  on this information, answer any four questions  from (a) to (e). 

 

(a) Identify A and C?  

(i) A – Al and C – Fe 

(ii) A – Fe and C – Al  

(iii) A – Mg and C- Al 

(iv) A – Al and C - Cu  

 

Answer

The reaction of a mixture of A and B in the presence of magnesium ribbon to form a liquid metal and oxide of D is the thermite reaction.

Thermite Reaction-01.jpg

According to this, A is Al because it is a grey colored metal and C is Fe because it forms rust in the presence of air and moisture.

 

So, the correct answer is (i) A - Al and C - Fe



(b) Identify B and D which are oxides of:  

(i) B – Fe, D – Al 

(ii) B – Mg, D – Al  

(iii) B – Al D - Cu 

(iv) B – Al D – Fe 

 

Answer

From the equation of thermite reaction,

Thermite Reaction-01.jpg

B is an oxide of Fe , and D of Aluminum .

The correct answer is (i) 

 

(c) Amphoteric oxides are:  

(i) Metal oxides which do not react with acids but react with bases.  

(ii) Metal oxides which react with both acids as  well as bases.  

(iii) Metal oxides which react with acids but do  not react with bases.  

(iv) Metal oxides which show no reaction with  either acids or bases.  

 

Answer

Ambhi means both. Therefore, the metal oxides which are able to react with both acid and base to form salt and water are known as amphoteric oxides.

Types of Oxides-01.jpg

So, the correct answer is (ii) Metal oxides which react with both acids as  well as bases.

 

(d) Which of the following is amphoteric in nature:  

(i) Both aluminium oxide and zinc oxide  

(ii) Only zinc oxide  

(iii) Only aluminium oxide  

(iv) Neither of them.  

 

Answer

Both aluminium oxide and zinc oxide are amphoteric in nature. Their reaction with acids and bases is given below:

Aluminium Oxide Acting as a Basic Oxide

Aluminium Oxide Acting as a Basic Oxide-01.jpg

Aluminium Oxide Acting as an Acidic Oxide

Aluminium Oxide Acting as a Acidic Oxide-01.jpg

Similarly, ZnO is also an amphoteric oxide.

Zinc Oxide Acting as a Basic Oxide

Zinc Oxide Acting as a Basic Oxide-01.jpg

Zinc Oxide Acting as an Acidic Oxide

Zinc Oxide Acting as a Acidic Oxide-01.jpg

 

So, the correct answer is (i)



(e) The reaction in which heat is generated is called as:  

(i) Exothermic reaction  

(ii) Endothermic reaction  

(iii) Decomposition reaction  

(iv) Precipitation reaction  

 

Answer

Exo means out and thermic means heat . Hence, the reactions in which heat is generated are known as exothermic reactions .

Endothermic vs Exothermic Reaction-01.jpg

So, the correct answer is (i) Exothermic reaction

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