Question

which of the following represents a synthesis reaction?
a $2h_2 + o_2 \
ightarrow 2h_2o$
b $2k + 2h_2o \
ightarrow 2koh + h_2$
c $2nacl \
ightarrow 2na + cl_2$
d none of the above.

Explanation:

Step1: Recall synthesis reaction definition

A synthesis reaction is \(A + B
ightarrow AB\) (two or more reactants combine to form one product).

Step2: Analyze each option

• Option a: \(2H_2 + O_2

ightarrow 2H_2O\) has two reactants (\(H_2\) and \(O_2\)) combining to form one product (\(H_2O\)), which fits the synthesis reaction pattern.

• Option b: \(2K + 2H_2O

ightarrow 2KOH + H_2\) is a single - replacement reaction (\(K\) replaces \(H\) in \(H_2O\)).

• Option c: \(2NaCl

ightarrow 2Na + Cl_2\) is a decomposition reaction (one reactant breaks into two products).

So, option a represents a synthesis reaction.

Answer:

A. \(2H_2 + O_2
ightarrow 2H_2O\)