Question

What type of reaction is $$Zn+2HCl\to ZnC{l}_2+H_2$$?
A) Combination reaction
B) Displacement reaction
C) Decomposition reaction
D) Double Displacement reaction

Answer 1

Hint: By looking at the chemical reaction it is easy to find out what type of reaction is following. Double displacement reactions are sometimes also known as double replacement reactions as only a molecule or element or a compound is getting replaced or displaced to form other different products.

Complete answer:
Now we discuss the option A) this is an incorrect option since, as we know, the combination reactions are those in which two or more elements/compounds react to form a single compound. Now we can see general equation for this type of reaction as,
$$X+Y\to XY$$
Option B) This is a correct option.
We have to know that the displacement reactions are the ones in which an atom or a group of atoms is displaced by another atom in a molecule. Now we can see general equation for this type of reaction as,
$$X+YZ\to XY+Z$$
$$Zn+2HCl\to ZnC{l}_2+H_2$$, this reaction follows this type of reaction thus this option is correct as $$Zn$$ metal is displacing $$H_2$$ from $$HCl$$.
Now we have to discuss the option C) this is an incorrect option as Decomposition reactions are the one in which a single compound breaks itself into smaller units or simpler substances. Now we can see general equation for this type of reaction as,
$$XY\to X+Y$$
Option D) this is an incorrect option, since in Double Decomposition reactions are the one in which the constituent charges of two reactants interchange themselves to form a new single compound. Now we can see general equation for this type of reaction as,
$$XY+ZA\to XZ+AY$$

Note:
We also need to know that the double displacement reaction requires two reactants having varying charge and as a product gives a new compound by interchanging the charges.
Displacement reactions are the one in which a group of atoms gets displaced by other atoms.