准确移取市售的双氧水15.00 mL,用直接法配制成250.00 mL,摇匀。再从其中准确吸出25.00 mL于锥形瓶中,加硫酸酸化后,用0.02068 mol/L KMnO4标准溶液滴定,终点时消耗KMnO4标准溶液26.42 mL,请计算样品中H2O2的含量。(H2O2的摩尔质量为34.02)
标定Na2S2O3溶液时,称得基准K2Cr2O7样品0.1506 g,酸化,并加入过量的KI,释放的I2用26.23 mL的Na2S2O3溶液滴定至终点,请计算Na2S2O3溶液的物质的量浓度。
Which of the following tag questions is INCORRECT?
A. Carry this parcel for me, will you?
B. Nobody wants to go there, does he?
C. Few people knew him, don’t they?
D. Everything is ready, isn’t it? do they?
_______ late again, Bill!
A. Don’t to be
B. Don't be
C. Not be
D. Be not