【单选题】
能使甲基橙指示剂变红，酚酞指示剂不显色的溶液是（ ） 溶液。
A. 盐酸
B. 氢氧化钠
C. 氯化钠
D. 碳酸氢钠
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答案
A
解析
暂无解析
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【单选题】
对水中钠离子进行测定时，加入碱化剂的作用是（ ）。
A. 防止水中阴离子的干扰
B. 调节水样pH值＞10，防止氢离子的干扰
C. 维持水样为中性
D. 防止水样中阳离子的干扰
【单选题】
柱塞泵与离心泵的启动方法不同之处是（ ）。
A. 柱塞泵是先开出、入口门，再启泵；离心泵是先开入口门，启泵后开出口门。
B. 柱塞泵是先开入口门，启泵后开出口门；离心泵是先开出、入口门，再启泵。
C. 柱塞泵是先开出、入口门，再启泵；离心泵是先启泵，再开出、入口门。
D. 柱塞泵是先启泵，再开出、入口门；离心泵是先开出、入口门，再启泵。
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