Question

What type of reaction is shown below? Check all that apply. Ca + 2H2O → Ca(OH)2 + H2 synthesis decomposition combustion single replacement double replacement

Answer 1

Answer:

The third option is correct which is single replacement.

Explanation:

Ca + 2H2O → Ca(OH)2 + H2 .

• In above reaction Ca take two OH- ions to become Ca(OH)2.
• So it is replacement of one type of atoms or ions (single replacement).
• If there is replacement of two type of ions/atoms then it will be double replacement.
• It is also not combustion or decomposition.

Answer 2

The balanced reaction is

Ca + 2H2O → Ca(OH)2 + H2

Here this reaction can be compared with

A + BC  ---> AB + C

So here one reactant (A) is accepting a group which is being given by another compound (BC) however the A is not giving any group / element or ion

So this single displacement

Similarly in the given reaction

the anion OH- is only being replaced

The element Ca accepts OH- and H2O loses the same group to form new element H2

So the correct answer is

Single replacement also known as single displacement