Question

On heating $ZnC{l_2}.2{H_2}O$, the compound obtained is:
A.$ZnC{l_2}$
B.$Zn(OH)Cl$
C.$Zn{(OH)_2}$
D.$ZnO$

Answer 1

On heating the compound breaks down into one more compound. And give the compounds as the product from which it is being formed. The reaction is usually an exothermic reaction i.e. which generates heat during reaction.

Complete step by step answer:
First of all let us talk about endothermic and exothermic reactions.
Exothermic reactions: They are defined as the energy which generates energy in the form of heat and light, known as exothermic reactions.
Endothermic reactions: They are defined as the reactions in which energy is required to start a reaction, are known as endothermic reactions.
When metals are heated then they generally form oxides. For example: when magnesium is heated in air then it forms magnesium oxide.
On heating the compound breaks down into one more compound. And give the compounds as the product from which it is being formed. The reaction is usually an exothermic reaction i.e. which generates heat during reaction.
Now in the question we are asked what happens when $ZnC{l_2}.2{H_2}O$ is heated. The reaction of heating of $ZnC{l_2}.2{H_2}O$ is as follows:
$ZnC{l_2}.2{H_2}O\xrightarrow{\Delta }Zn(OH)Cl + HCl + {H_2}O$. On heating it gives $HCl$, ${H_2}O$ and $Zn(OH)Cl$.

Hence option B is correct.

Additional information:
Let us read about what is reactant and product.
Reactants: During reaction the reagents which react with each other to form a new compound, are known as reactants. For example: in the question the reactant will be $ZnC{l_2}.2{H_2}O$.
Products: During reaction the new compounds which are formed due to the reaction, are known as products. Here in the question $HCl$, ${H_2}O$ and $Zn(OH)Cl$ act as products.
When we heat any compound then the atoms or molecules by which compound are formed vibrate faster. Some compounds can be decomposed by small amounts of heat as well. For example: calcium carbonate decomposes to calcium oxide and carbon dioxide. The reaction is as:
$CaC{O_3}\xrightarrow{\Delta }CaO + C{O_2}$. Another example of decomposition of compounds is hydrogen peroxide. As light falls on hydrogen peroxide it gives water and oxygen as products.

Note:
Generally sodium carbonate and potassium carbonate are not decomposable because they have ionic bonds which are strong and hard to break in comparison of covalent bonds and coordinate bonds.