(1)CH3COOH是弱电解质,c(CH3COOH)大于其溶液中c(H+),所以pH=0的醋酸溶液中醋酸浓度大于1mol/L;
CH3COOH在稀释过程中c(CH3COOH)减小、n(CH3COOH)不变,浓醋酸浓度大于1mol/L,则所用CH3COOH溶液的体积小于10mL,
故答案为:大于;小于;
(2)混合后充分反应,测得各离子浓度大小顺序为:[K+]>[CH3COO-]>[OH-]>[H+],溶液呈碱性,溶液中的溶质可能是CH3COOK、CH3COOK和少量KOH或CH3COOK和极少量的CH3COOH,则体积a均有可能,故答案为:均可能;
(3)当混合后溶液pH=7时,溶液呈中性,则[OH-]=[H+],再结合电荷守恒得:[K+]=[CH3COO-],水的电离程度很小,则溶液中离子浓度大小顺序是:[K+]=[CH3COO-]>[OH-]=[H+]; CH3COOK溶液呈碱性,要使 CH3COOH和KOH混合溶液呈中性,则 CH3COOH应该稍微过量,则a小于100mL,
故答案为:[K+]=[CH3COO-]>[OH-]=[H+];小于.