问题 填空题

下图是常见固体物质的溶解度曲线,根据图示回答:

(1)曲线上点A表示______;

(2)有A、B、C三只试管放在盛有冷水的烧杯中(如图所示),向烧杯中加入适量浓硫酸,观察到______,此时B试管中溶液的状态______(填“饱和”或“不饱和”)

(3)20℃时,将40 g食盐放入100g水中充分溶解,所得溶液中溶质的质量分数约为______,做的理由是______.

答案

(1)由溶解度曲线图可知A点表示:t℃时,硝酸钾和食盐的溶解度相同.

(2)向烧杯中加入适量浓硫酸,浓硫酸遇水会放出热量,由溶解度曲线图可知硝酸钾的溶解度随温度升高而升高.所以A中硝酸钾固体减少.而C中氢氧化钙的溶解度随温度的升高而降低,所以C试管中变浑浊.而氯化钠的溶解度受温度影响不大,但溶解度也升高.所以B中溶液会变成为不饱和溶液.

(3)20℃时,食盐的溶解度为37g,所以将40 g食盐放入100g水中充分溶解,所得溶液中溶质的质量分数约为

37g
37g+100g
×100%=27%.

故答案为:(1)t℃时,硝酸钾和食盐的溶解度相同.

(2)A中固体减少,C中出现浑浊,不饱和.

(3)27.0%;20℃时40 g食盐未完全溶解,只溶解了大约37g.

完形填空
完形填空。
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