Answer
a. HCLO4: perchloric acid
b. HNO3: nitric acid
c. HCN: hydrocyanic acid
d. H2S: hydrogen sulfide
Work Step by Step
a. ClO4- = perchlorate --> +H = perchloRIC acid (ate -> ic)
b. NO3 = nitrate = nitric = nitric acid
c. CN- = cyanide = hydro+cyanic acid
d. H2S = hydrogen + sulfide