Question

answer this
question is in the attachment​

Answer 1

ANSWER

In case (B) ,(C)and (D) the reactions that involved are chemical reactions.

Step By Step Explanation

In case (A)

-Hydrated CuSo4 Crystals are of blue colour which means it contains it contains water if crystallization.

-In heating these crystals the molecules loses the water if crystallization and forms a white salt.

-Reaction >

CuSO4.5H20 => CuSO4 + 5H2O

Since this process can be reversed by hydration of CUSO4, this is Reversible Chemical reaction.

In case (2)

-When lead nitrate is heated then it decomposes to firm Lead oxide,nitrogen dioxide and oxygen.

-This is a chemical reaction i.e decomposition reaction which is irreversible.

-Reaction >

2Pb(No3)2 =>2Pbo + 4No2 + O2

In case (3)

-Dissolving of Ammonium Chloride in water is a acidic this salt dissolves in water to dissociate its ions.

-This is a irreversible change as the salt cannot be obtained from water.

-Reaction>

NH4Cl + H2O =>${NH4}^{+} + {Cl}^{-}$

In case (4)

-When ferrous sulphate crystals are heated them it undertakes decomposition reaction and forms Ferric oxide, sulphur dioxide and sulphur trioxide.

-This is a irreversible change and new products are formed.Which means it is chemical change.

-Reaction >

FeSo4 => Fe2O3 + SO2 + SO3

REMEMBER

- A chemical change is always irreversible and new substances are formed .

-A physical change is Reversible and new substances may not be formed.

Answer 2

$\bold{CHEMICAL \: CHANGE }$

Chemical change is the one that is carried out by the change in the composition of that substance.

So,

$\bold{Options \: B \: ,C \:and \: D \: are \: correct }$

$\bold{REASON }$

◼For option A

Copper sulphate when heated loses its water molecules and becomes anhydrous copper sulphate. Since, the reaction is reversible its a physical change.

${CuSO_4.5H_2O \xrightarrow{heat} CuSO_4 + 5H_2O}$

◼For option B

When lead nitrate is heated it gives out lead oxide , oxygen and a reddish-brown gas nitrogen dioxide. Since, the product formed completely differs from the composition of original substance, and change is not reversible its a chemical change.

${Pb(NO_3)_2 \xrightarrow{heat} PbO + O_2 + 4NO_2}$

◼For option C

When ammonium chloride is added to water it gives out ammonia and hydrochloric acid. Since, the product formed completely differs from original substance as it was an acid salt while it gives out a pungent smelling gas and an acid and also the change isn't reversible so its a chemical change.

${NH_4Cl \xrightarrow{heat} NH_3 + HCl}$

◼For option D

When ferrous sulphate salt is heated it gives out ferric oxide, sulphur dioxide and sulphur tri oxide and its green colour changes to white .since, there is change in composition and reaction is irreversible .Its an chemical reaction. .