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用铬合滴定法测定水的硬度时，冬季水温较低时，络合反应速度（），容易造成滴定（）而产生误差。因此，当温度较低时，应将水样预先（）后进行测定。

答案

参考答案：较慢；过量；加温至30～40℃

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Some consumer researchers distinguish_____(1) "rational" motives and "emotional" (or "non-rational") motives. They use the term "rationality"_____(2) the traditional economic sense that assumes_____(3) consumers behave rationally when they carefully consider all alternatives_____(4) choose those that give them the greatest utility (i.e., satisfaction). _____(5) a marketing context, the term "rationality" implies that the consumer selects goods based_____(6) totally objective criteria, such_____(7) size, weight, price, and so on. "Emotional" motives imply the selection of goods____(8) to personal or subjective criteria — the desire_____(9) individuality, pride, fear, affection or status.The assumption underlying this distinction is____(10) subjective or emotional criteria do not maximize utility or satisfaction. _____ (11), it is reasonable to assume that consumers always attempt to select alternatives that, ____(12) their view, serve to maximize satisfaction. Obviously, the assessment of satisfaction is a very personal process, based_____(13) the individual’’s own needs as_____(14) as on past behavioral, social, and learning experiences. What may appear_____(15) irrational to an outside observer may be perfectly rational ______(16) the context of the consumer’’s own psychological field. For example, a product purchased to enhance one’’s self-image (such as a fragrance) is a perfectly rational form of consumer behavior. ____(17) behavior did not appear rational to the person who undertakes it_____ (18) the time that it is undertaken, obviously he or she would not do it._____(19) the distinction between rational and emotional motives does not appear to be warranted.Some researchers go so far_____(20) to suggest that emphasis_____ (21) "needs" obscures the rational, or conscious, nature of most consumer motivation. They claim that con sumers act consciously____(22) maximize their gains and minimize their losses; that they act not____(23) subconscious drives but from rational preferences,____(24) what they perceive to be_____(25) their own best interests.
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解答题

已知函数f（x）=-x3+ax2+b（a，b∈R）

（1）若函数f（x）在（0，2）上是增函数，求实数a的取值范围；

（2）设x1，x2，x3为方程f（x）=0的三个根，且x1∈（-1，0），x2∈（0，1），x3（-∞，-1）∪（1，+∞），求证：|a|＞1．
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