Question

which of the following reactions are single replacement reactions?
ca + s → cas
k + agcl → ag + kcl
nacl → na + cl2
ch4 + o2 → h2o + co2
naoh + hcl → hoh + nacl
na + hcl → h2 + nacl

Explanation:

Step1: Recall single - replacement reaction definition

A single - replacement reaction has the general form $A + BC
ightarrow B+AC$, where an element replaces another element in a compound.

Step2: Analyze each reaction

• For $Ca + S

ightarrow CaS$, it is a combination reaction ($A + B
ightarrow AB$), not a single - replacement reaction.

• For $K + AgCl

ightarrow Ag+KCl$, potassium ($K$) replaces silver ($Ag$) in silver chloride ($AgCl$), so it is a single - replacement reaction.

• For $NaCl

ightarrow Na + Cl_2$, it is a decomposition reaction ($AB
ightarrow A + B$), not a single - replacement reaction.

• For $CH_4+O_2

ightarrow H_2O + CO_2$, it is a combustion reaction, not a single - replacement reaction.

• For $NaOH + HCl

ightarrow HOH+NaCl$, it is a double - replacement reaction ($AB + CD
ightarrow AD+CB$), not a single - replacement reaction.

• For $Na + HCl

ightarrow H_2+NaCl$, sodium ($Na$) replaces hydrogen ($H$) in hydrochloric acid ($HCl$), so it is a single - replacement reaction.

Answer:

$K + AgCl
ightarrow Ag + KCl$, $Na + HCl
ightarrow H_2+NaCl$