1
Q:

Which of the following reactions are redox reactions?

A) Ba(s)+Cl2(g)--->BaCl2(s) B) Mg(s)+Br2(l)--->MgBr2(s)
C) Al(s)+3Ag^+(aq)--->Al^3+(aq)+3Ag(s) D) All of the above

Answer:   D) All of the above



Explanation:

A redox reaction is a type of reaction which involves transfer of electrons among two species. This reaction is also called oxidation-reduction reaction.

In oxidation process, there is an increase in oxidation state of an atom, ion or molecule by losing the electrons.

In reduction process, there is a decrease in oxidation state of an atom, ion or molecule by accepting the electrons.

1)

image

In this reaction, Ba undergoes oxidation and Cl undergoes reduction.
This reaction is redox reaction.
In this reaction, oxidation number of Ba increases from 0 to +2 . So, Ba undergoes oxidation. The oxidation number of Cl decreases from 0 to -1. So, Cl undergoes reduction.

 

2) 

 

image

From this above reaction, it is clear that Aluminum undergoes oxidation and silver undergoes reduction.
Due to this, this reaction is redox reaction.

In this reaction, oxidation number of Aluminum increases from 0 to +1. So, aluminum undergoes oxidation. The oxidation number of silver decreases from +1 to 0. So, silver undergoes reduction.

 

3)


image

In this reaction, Mg undergoes oxidation and Br undergoes reduction.
This reaction is redox reaction.
The reactions 1, 3 and 4 are redox reactions.
In this reaction, oxidation number of Mg increases from 0 to +2 . So, Mg undergoes oxidation. The oxidation number of Br decreases from 0 to -1 . So, Br undergoes reduction.

 

Hence all the above reactions are redox reactions.

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The percentage of nitrogen in the air is about

A) 74% B) 76%
C) 78% D) 80%
 
Answer & Explanation Answer: C) 78%

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Methane contributes towards global warming so it is called a _________________ gas.

 

A) poisonous B) carcinogenic
C) infectious D) greenhouse
 
Answer & Explanation Answer: D) greenhouse

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Which of the following is a metal?

 

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C) Oxygen D) No option is correct
 
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Which of the following group is NOT Dobereiner Triads?

 

A) Li, Na, K B) N, P Au
C) Cl, Br, I D) Ca, Sr, Ba
 
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1 6508
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Safety matches contain

A) Sulphur B) Phosphorus
C) Magnesium D) Potassium
 
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Air ___________________ are the substances which contaminate the air.

A) Reactants B) Irritants
C) Resistants D) Pollutants
 
Answer & Explanation Answer: D) Pollutants

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By using which foam the Researchers from Indian Institute of Technology – Bombay have made a low cost piezo resistive vibration sensor?

A) Only Polyurethane B) Only Polyethylene
C) Both Polyurethane and Polyethylene D) Neither Poly urethane nor Polyethylene
 
Answer & Explanation Answer: B) Only Polyethylene

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Which of the following is NOT a compound?

 

A) Ammonia B) Milk
C) Sodiumchloride D) Chalk
 
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