Question

which of the following reactions are synthesis reactions?
□ k + cl₂ → kcl
□ na + hcl → h₂ + nacl
□ ch₄ + o₂ → h₂o + co₂
□ naoh + hcl → hoh + nacl
□ nacl → na + cl₂
□ h₂ + o₂ → h₂o

Explanation:

Step1: Recall synthesis - reaction definition

A synthesis reaction is a reaction where two or more substances combine to form a single product.

Step2: Analyze each reaction

• For \(K + Cl_2

ightarrow KCl\): Two substances \(K\) and \(Cl_2\) combine to form one product \(KCl\), so it is a synthesis reaction.

• For \(Na + HCl

ightarrow H_2+NaCl\): This is a single - replacement reaction where \(Na\) replaces \(H\) in \(HCl\), not a synthesis reaction.

• For \(CH_4 + O_2

ightarrow H_2O+CO_2\): This is a combustion reaction, not a synthesis reaction.

• For \(NaOH + HCl

ightarrow HOH + NaCl\) (which is \(NaOH + HCl
ightarrow H_2O+NaCl\)): This is a double - replacement (acid - base neutralization) reaction, not a synthesis reaction.

• For \(NaCl

ightarrow Na + Cl_2\): This is a decomposition reaction where one substance breaks into two substances, not a synthesis reaction.

• For \(H_2+O_2

ightarrow H_2O\): Two substances \(H_2\) and \(O_2\) combine to form one product \(H_2O\), so it is a synthesis reaction.

Answer:

\(K + Cl_2
ightarrow KCl\), \(H_2+O_2
ightarrow H_2O\)