Question

5. Which of the following is a synthesis reaction? (2 points)

Answer 1

2H2 + O2 = 2H2O since two elements created a compound, in this case water.

Answer 2

Answer: The correct answer is $2H_2+O_2\rightarrow 2H_2O$

Explanation:

Synthesis reaction is defined as the reaction in which two smaller substances combine together to form a large single compound.

$A+B\rightarrow AB$

From the given options:

Option A:  $2H_2+O_2\rightarrow 2H_2O$

This is a synthesis reaction and only one product is forming.

Option B:  $2H_2O_2\rightarrow 2H_2O+O_2$

This is a decomposition reaction.

Option C:  $CaCO_3\rightarrow CaO+CO_2$

This is a decomposition reaction.

Option D:  $2AgNO_3+Zn\rightarrow 2Ag+Zn(NO_3)_2$

This is a single displacement reaction.

Thus, the correct answer is $2H_2+O_2\rightarrow 2H_2O$