Listen to the following conversations, paying special attention to the sentence stress. Underline the information words. Example: Would you like an apple or a banana ?
【单选题】纯 NaOH 、 NaHCO 3 固体按 1:3 的物质的量溶于水中摇匀后,再用双指示剂法测定。已知酚酞、甲基橙变色时,滴入 HCl 标准溶液分别为 V 1 和 V 2 ,则 V 1 / V 2 为( ) ( 已知 H 2 CO 3 : p K a1 = 6.38 , p K a2 = 10.25 )