A: lead oxide

B: nitrogen dioxide

C: oxygen

D: nitrogen

Solution:

Correct Option is: (A), (B) And (C)

lead oxide, nitrogen dioxide and oxygen

Explanation :

The molecular formula for lead nitrate is Pb(NO₃)₂.

 When lead nitrate is heated it decomposes to lead oxide, nitrogen dioxide and oxygen.

2Pb(NO₃)₂.→  2PbO+4NO₂+ O₂

The colour on adding copper is:

A: blue

B: black

C: brown

D: no change in colour

Solution:

Correct Option is: (D)

no change in colour

Explanation :

• Less reactive metal is not able to displace more reactive elements from its compound.
• As copper is less reactive metal than zinc 
• Copper cannot displace zinc from zinc sulphate.
• Zinc sulphate will not react with copper 
• Hence  no reaction will take place 

nitrate, a yellow precipitate of lead iodide is formed. While performing the activity if lead nitrate is not available,

which of the following can be used in place of lead nitrate?

A: Lead sulphate (insoluble)

B: Lead acetate

C: Ammonium nitrate

D: Potassium sulphate

Solution:

Explanation : 

2KI(aq) + Pb(NO₃)₂​(aq)→PbI₂(s) + 2KNO₃

Lead acetate  reacts with potassium iodide dissolved in water to give acetate ion and lead ion 

The lead ion combines with the iodine ion and form lead iodide 

Potassium ion combines with acetate ion and forms potassium acetate.  . 

2KI(aq)+Pb(CH₃COO)₂ (aq)→PbI₂ (s) + 2CH₃COOK

 Hence , lead acetate can be used in place of lead nitrate .

Final Answer : Hence the correct option is (B) Lead acetate.

A: Sodium

B: Calcium

C: Iron

D: None of the above

Solution:

Explanation : 

Sodium is kept immersed in kerosene because it is very reactive in nature and catches fire when kept in open condition.

So to prevent fire it is kept immersed in kerosene.

Final Answer : Hence the correct answer is (A)

(a) Displacement

(b) Precipitation

(c) Combination

(d) Double displacement

A: (a) & (c)

B: (a), (b) & (c)

C: (b) & (c)

D: (b) & (d)

Solution:

Explanation :

A reaction in which more reactive element displaces less reactive element is known as displacement reaction.

While a  reaction in which mutual exchange of ions or molecules takes place in between compounds is known as Double displacement reaction.

BaCl₂(aq) + Na₂SO₄(aq)→ BaSO₄₍s) + 2NaCl (aq)

Here ions  are  mutually exchanged  by each other so it is a double displacement reaction.

Also this reaction leads to the formation of white precipitate BaSO₄ So it is also a precipitation reaction. 

Final Answer : Hence the correct answer is (D) (b) & (d).