Question

Which of the following is a double replacement reaction? Ca(OH)2 + H2SO4 → CaSO4 + 2H2O CH4 + 2O2 → CO2 + 2H2O 8Fe + S8 → 8FeS Zn + H2SO4 → ZnSO4 + H2

Answer 1

That would be the first option Ca(OH)2 + H2SO4 → CaSO4 + 2H2O.

The Ca replaces the H2 in H2SO4, and the H2 replaces the Ca is Ca(OH)2.

Answer 2

Answer: Option (a) is the correct answer.

Step-by-step explanation:

A chemical reaction in which there occurs exchange of two ions between two different compounds is known as a double replacement reaction.

For example,
`Ca(OH)_(2) + H_(2)SO_(4) \rightarrow CaSO_(4) + 2H_(2)O`

Here,
`OH^(-)` ions of
`CaOH_(2)` is replaced by
`SO^(21)_(4)` ions of sulfuric acid and
`SO_(4)` of sulfuric acid is replaced by
`OH^(-)` ions of
`CaOH_(2)`.

When two atoms combine together to form a compound then it is known as synthesis reaction.

When a compound reacts with oxygen to give carbondioxide and water then it is known as combustion reaction.

When a metal is treated with an acid to yield hydrogen gas then it is known as single replacement reaction.

Therefore, we can conclude that
`Ca(OH)_(2) + H_(2)SO_(4) \rightarrow CaSO_(4) + 2H_(2)O` is a double replacement reaction.