一种未知白色粉末药品(有可能是 Na 2 CO 3 、 NaHCO 3 和 NaOH 这三种物质中的一种或两种物质混合物)配成的溶液,现用双指示剂法(酚酞和甲基橙)用盐酸标准溶液进行滴定,当酚酞指示剂由红色完全褪去所消耗盐酸体积为 V 1 ,再加入甲基橙继续滴定,当甲基橙由黄色变为橙色时所消耗盐酸的体积为 V 2 。当 V 1 ≠0,V 2 >V 1 时,粉末的组成是:
【简答题】词汇考查: 1. Work harder, and you'll make great p________ in your English. 2. Don't knock at the door like that! lt's w________. 3. You're getting heavier and you'd better lose some w________ to keep fit....