Chapter Five 15.4 Write the formulas of the conjugate bases of the following acids:(a) HNO2,(b)H2SO4,(c)H2S ,(d)HCN,(e)HCOOH(formic acid) Answer:(a)HNO2→NO2;(B)HSO4→HSO4;(c)HS→HS；,(d) HCN→CN,e)HCOOH→HCOO 15.9What is the ion-product constant for water? Answer:K=[OH][H']=1.0x1014 15.27 Explain what is meant by the strength of an acid. It means how an acid is strong or weak by calculating its K,i.e.,whether it is easy to release H'or not,if it is easy then it is a strong acid. Chapter Six 16.56 Question find the approximate PH range suitable for the separation of Fe and Zn2ions by precipitation of Fe(OH)3 from a solution that is initially 0.001M in both Feand Zn2 Answer:the solubility equilibrium for Fe(OH)3 is Fe(OH)3(s)Fe(aq)+30H(aq) Ksp=Fe]OH-P Because Fe"(aq)=0.010M,the concentration of OH that must be exceeded to initiate the precipitation of Fe(OH)3 isChapter Five 15.4 Write the formulas of the conjugate bases of the following acids: (a) HNO2, (b) H2SO4 ,(c) H2S ,(d) HCN ,(e) HCOOH(formic acid). Answer：(a) HNO2→ NO2 - ; (B) H2SO4→ HSO4 - - ; (c) H2S→ HS ; ,(d) HCN → CN- ; e) HCOOH→ HCOO- . 15.9What is the ion-product constant for water? - Answer: Kw Θ = [OH ][H+ ] = 1.0x10-14 15.27 Explain what is meant by the strength of an acid. It means how an acid is strong or weak by calculating its Ka, i.e., whether it is easy to release H+ or not, if it is easy then it is a strong acid. Chapter Six 16.56 Question find the approximate PH range suitable for the separation of Fe3+ 2+ and Zn ions by precipitation of Fe(OH)3 from a solution that is initially 0.001M in both Fe3+ 2+ and Zn . Answer: the solubility equilibrium for Fe(OH)3 is Fe(OH)3(s) ⇔ Fe3+ - (aq) + 3OH (aq) [ ] 3 − [ ] OH 3+ KSP = Fe [ ] 3+ Fe (aq) = 0.010M , the concentration of [ ] − Because OH that must be exceeded to initiate the precipitation of Fe(OH)3 is