Question

from your work on the previous screen, you saw that double - replacement reactions follow the following general pattern: ab + cd → ad + cb based on this, which of the reactions below are double - replacement reactions? pb(no₃)₂(aq) + 2ki(aq) → 2kno₃(aq) + pbi₂(s) 2agno₃(aq) + zn(s)2ag(s) + zn(no₃)₂(aq) mg(s) + 2hcl(aq) → mgcl₂(aq) + h₂(g) bacl₂(aq) + na₂so₄(aq) → baso₄(s) + 2nacl(aq)

Explanation:

A double - replacement reaction has the general form \(AB + CD
ightarrow AD+CB\). In the reaction \(Pb(NO_3)_2(aq)+2KI(aq)
ightarrow 2KNO_3(aq)+PbI_2(s)\), \(AB = Pb(NO_3)_2\) (\(A = Pb^{2 +}\), \(B=NO_3^{-}\)), \(CD = KI\) (\(C = K^{+}\), \(D = I^{-}\)), and the products are \(AD = PbI_2\) and \(CB=KNO_3\). In the reaction \(BaCl_2(aq)+Na_2SO_4(aq)
ightarrow BaSO_4(s)+2NaCl(aq)\), \(AB = BaCl_2\) (\(A = Ba^{2+}\), \(B = Cl^{-}\)), \(CD=Na_2SO_4\) (\(C = Na^{+}\), \(D = SO_4^{2 -}\)), and the products are \(AD = BaSO_4\) and \(CB = NaCl\).

The reaction \(2AgNO_3(aq)+Zn(s)
ightarrow 2Ag(s)+Zn(NO_3)_2(aq)\) is a single - replacement reaction (\(A + BC
ightarrow AC + B\) where \(A = Zn\), \(B = Ag\), \(C=NO_3^{-}\)). The reaction \(Mg(s)+2HCl(aq)
ightarrow MgCl_2(aq)+H_2(g)\) is also a single - replacement reaction (\(A + BC
ightarrow AC + B\) where \(A = Mg\), \(B = H\), \(C = Cl^{-}\)).

Answer:

\(Pb(NO_3)_2(aq)+2KI(aq)
ightarrow 2KNO_3(aq)+PbI_2(s)\) and \(BaCl_2(aq)+Na_2SO_4(aq)
ightarrow BaSO_4(s)+2NaCl(aq)\) are double - replacement reactions.