Which equation is a redox process?

Question

#1.# #NaBr(aq) + HCl(aq) rightleftharpoons NaCl(aq) + HBr(aq)#

#2.# #HBr(aq) + AgNO_3(aq) rarr AgBr(s)darr + HNO_3(aq)#

#3.# #H_2(g) + Br_2(g) rarr 2HBr(g)#

#4.# #2NaOH(aq) + H_2SO_4(aq) rarr Na_2SO_4(aq) + 2H_2O(l)#

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Answer 1 · 2016-06-20T06:20:48

Only #(3)# exhibits redox, formal electron transfer.

#NaBr(aq) + HCl(aq) rightleftharpoons NaCl(aq) + HBr(aq)#

#HBr(aq) + AgNO_3(aq) rarr AgBr(s)darr + HNO_3(aq)#

#H_2(g) + Br_2(g) rarr 2HBr(g)#

In this reaction zerovalent bromine oxidizes zerovalent hydrogen to give #H^(I+)Br^(-I)# as the redox product.

#2NaOH(aq) + H_2SO_4(aq) rarr Na_2SO_4(aq) + 2H_2O(l)#