Question

kbr + agno3 -- kno3 + agbr
zn + 2hcl -- h2 + zncl2
mgco3 -- mgo + co2
2fe(oh)3 -- fe2o3 + 3h2o
na2co3 + ca(oh)2 -- caco3 + 2naoh
agno3 + hcl -- agcl + hno3
out of the chemical equations above, how many are considered to be double-replacement reactions?
(your answer should be a number, like 7 or 9)

Explanation:

Step1: Recall double - replacement reaction definition

A double - replacement reaction has the general form \(AB + CD
ightarrow AD+CB\).

Step2: Analyze each reaction

• For \(KBr + AgNO_{3}

ightarrow KNO_{3}+AgBr\), it is a double - replacement reaction (\(AB = KBr\), \(CD = AgNO_{3}\), \(AD = KNO_{3}\), \(CB=AgBr\)).

• For \(Zn + 2HCl

ightarrow H_{2}+ZnCl_{2}\), it is a single - replacement reaction (\(Zn\) replaces \(H\) in \(HCl\)).

• For \(MgCO_{3}

ightarrow MgO + CO_{2}\), it is a decomposition reaction.

• For \(2Fe(OH)_{3}

ightarrow Fe_{2}O_{3}+3H_{2}O\), it is a decomposition reaction.

• For \(Na_{2}CO_{3}+Ca(OH)_{2}

ightarrow CaCO_{3}+2NaOH\), it is a double - replacement reaction (\(AB = Na_{2}CO_{3}\), \(CD = Ca(OH)_{2}\), \(AD = 2NaOH\), \(CB = CaCO_{3}\)).

• For \(AgNO_{3}+HCl

ightarrow AgCl + HNO_{3}\), it is a double - replacement reaction (\(AB = AgNO_{3}\), \(CD = HCl\), \(AD = HNO_{3}\), \(CB = AgCl\)).

Answer:

\(3\)