【单选题】用 EDTA 滴定 Ca 2+ 、 Mg 2+ ,若溶液中存在少量 Fe 3+ 和 Al 3+ 将对测定有干扰,消除干扰的方法是
A.
加 KCN 掩蔽 Fe 3+ ,加 NaF 掩蔽 Al 3+
B.
加入抗坏血酸将 Fe 3+ 还原为 Fe 2+ ,加 NaF 掩蔽 Al 3+
C.
采用沉淀掩蔽法,加 NaOH 沉淀 Fe 3+ 和 Al 3+
D.
在酸性条件下 , 加入三乙醇胺,再调到碱性以掩蔽 Fe 3+ 和 Al 3+
【简答题】--How many apples do you want? --_________ (1.5分)A. 2yuan a kilo. It’s on sale
now. B. I’ll take 5kilos C. It’s five D. It’s too expensive.
【单选题】You’re sitting in a café with a friend, andyou see someone you find attractive looking at you. He comes over and says to you, “Good to see you. So how was your weekend?” What do you think or say?
A.
I’m so embarrassed. What do I say?
B.
“I’m sorry. Have we met before?”
C.
“It was great. Thank you. How about you?”
D.
“My memory is awful. I can’t remember if we already met.”
【单选题】用 EDTA 滴定 Ca 2+ 、 Mg 2+ ,若溶液中存在少量 Fe 3+ 和 Al 3+ ,将对测定有干扰,消除干扰的方法是
A.
加 KCN 掩蔽 Fe 3+ ,加 NaF 掩蔽 Al 3+
B.
加抗坏血酸将 Fe 3+ 还原为 Fe 2+ ,加 NaF 掩蔽 Al 3+
C.
采用沉淀掩蔽法,加 NaOH 沉淀 Fe 3+ 和 Al 3+
D.
加入三乙醇胺以掩蔽 Fe 3+ 、 Al 3+
【单选题】在pH=10时用EDTA滴定Ca2+、Mg2+,溶液中若存在少量Al3+将对测定有干扰,消除干扰最方便的方法是( )
【单选题】- Andy, _______ do you like the film Zootopia? -________, but I think the music is wonderful. A. how, Great B. what, Great C. how, Not bad D. what, Not bad
【单选题】用EDTA滴定Ca2+、Mg2+,若溶液中存在少量Fe3+将对测定有干扰,消除干扰的方法是:
【判断题】志存高远的人,再遥远的地方也能达到,再坚固的东西也能突破。