Which reaction is not a redox reaction?
a. H2s(g) + cl2(aq) 2hcl(aq) + s(s)
b. Zn(s) + 2hcl(aq) zncl2(aq) + h2(g)
c. Ag+(aq) + cl (aq) agcl(s)
d. 3h2(g) + n2(g) 2nh3(g)?