用盐酸测定碳酸钠时既可用酚酞作指示剂又可用甲基橙(一种酸碱指示剂)作指示剂,现分别用酚酞和甲基橙作指示剂,用0.1000mol/L的HCl滴定20.00mL的纯碱溶液,滴定终点时分别用去了20.00mL、40.00mL的盐酸,下列说法中不正确的是 ( )
A.用酚酞作指示剂时滴定的总反应为:Na2CO3+HCl=NaHCO3+NaCl |
B.用甲基橙作指示剂时滴定的总反应为:Na2CO3+2HCl=NaCl+CO2↑+H2O |
C.可用碱式滴定管量取所需要的Na2CO3溶液 |
D.若酸式滴定管没有用标准溶液润洗,则所测得的碳酸钠溶液浓度偏低 |
The CDs are on sale! Buy one and you get ______ completely free.
A.other | B.others | C.one | D.ones ks |
I’m sure that your letter will get______ attention. They know you’re waiting for the reply.
A.continued | B.immediate | C.careful | D.general |
All the dishes in this menu, ______ otherwise stated, will serve two to three people.
A.as | B.if | C.though | D.unless |
The children loved their day trip, and they enjoyed the horse ride ______.
A.most | B.more | C.less | D.little |
Progress______ so far very good and we are sure that the work will be finished on time.
A.was | B.had been | C.has been | D.will be |