【单选题】下列物质中,不能用NaOH标准溶液直接准确滴定的是()。
【单选题】下列物质中,不能用 NaOH 标准溶液直接准确滴定的是( ) ( 已知 H 2 CO 3 : p K a1 = 6.38 , p K a2 = 10.25 ;邻苯二甲酸: p K a1 = 2.95 , p K a2 = 5.41 ;六亚甲基四胺: p K b = 8.85 )
【简答题】下列酸溶液能否用 NaOH准确滴定或准确分步滴定(浓度均为0.1mol/L), 请在备择答案(A,B,...)中选择正确答案: (1) 酒石酸(p K a1 = 3.04、p K a2 = 4.37) __ __ (2) 柠檬酸(p K a1 = 3.13、p K a2 = 4.76、p K a3 = 6.60) __ __ (3) 亚磷酸(p K a1 = 1.30、p K a2 = 6.60...
【单选题】下面SQL正确的是?
A.
SELECT * FROM Tb_Stu_Score WHERE score>=80
B.
SELECT * FROM Tb_Stu_Score WHERE score BETWEEN 70 AND 80
C.
SELECT * FROM Tb_Stu_Info WHERE Stu_Address in ('湖北荆州','浙江温州')
D.
SELECT * FROM Tb_Stu_Info WHERE Stu_Address = '湖南%'
【单选题】下列酸溶液不能用 NaOH 准确滴定 ( 浓度均为 0.1 mol.L -1 ) 的是
【单选题】下面SQL语句不正确的是
B.
update user set usernamezhangsan' where id2'
D.
insert into user values( lzhang ,'pass')