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估算法是根据题目给定的条件或数量关系不经精确计算,只经分析、推理或进行简单的推算就能找出答案的一种解题方法．例1 把1．6 g无水CuSO4投入100 gt℃时饱和CuSO4溶液中,析出晶体的质量约为 ( )(t℃时CuSO4的溶解度约为20 g) (A)1．6 g (B)2．5 g (C)2．8 g (D)3．2 g 解析:1．6 g无水CuSO4投入溶液,由于析出CuS04·5H2O,故析出晶体质量必大于1．6 g．又1．6 g CuSO4→CuSO4·5H2O应生成2．5 g,但由于带走结晶水又会有少量晶体析出,故可排出选项(A)、(B)再根据溶解度求得(C)为选项．
The estimation method is a problem-solving method that can find out the answer based on the condition or quantity relationship given by the topic without accurate calculation, analysis, reasoning or simple calculation. Example 1 When 1.6 g of anhydrous CuSO4 is put into a saturated CuSO4 solution at 100 gtC, the mass of the precipitated crystal is approximately () (The solubility of CuSO4 is about 20 g at t°C) (A) 1.6 g (B) 2.5 g (C) 2.8 g (D) 3.2 g Analysis: 1.6 g anhydrous CuSO4 input solution, due to the precipitation of CuS04 · 5H2O, the precipitation crystal quality must be greater than 1.6 g. Another 1.6 g of CuSO4→CuSO4·5H2O should generate 2.5 g, but since crystal water will be carried away, a small amount of crystals will precipitate. Therefore, options (A) and (B) can be discharged and the solubility can be obtained (C). Options.