20 g烧碱配制成500 mL溶液，其物质的量浓度为________mol·L－1；从中取出1 mL，其物质的量浓度为________mol·L－1，含溶质______g。若将这1 mL溶液用水稀释到100 mL，所得溶液中溶质的物质的量浓度为__________mol·L－1，其中含Na＋______g。
1；1；0.04；0.01；0.023
20g烧碱的物质的量是0.5mol，所以浓度是0.5mol÷0.5L＝1.0mol/L；溶液是均一的，因此取出的1ml溶液浓度仍然是1mol/L；其中含有氢氧化钠的质量是20g÷500＝0.04g；稀释过程中溶质是不变的，所以稀释溶液的浓度是1mol/L÷100＝0.01mol/L，其中钠离子的质量是0.023g。
| 完型填空：先阅读短文，然后根据短文内容选出一个最佳答案填空。 | ||||
| One day Mrs Jones went 1 . When her 2 came home in the evening, she began to tell him about a beautiful cotton 3 . "I saw it in a shop this morning." She said. "And…" "And you were going to buy it." said Mr Jones. "How 4 is it?" "Fifty pounds." "Fifty pounds for a dress? That's too 5 ." But every evening when Mr Jones came back from his work, his wife began to speak only about the dress. And at last after a week, he said, "OK, buy the dress. Here is the 6 ." She was very 7 . But the next evening, when Mr Jones came home and asked, "Have you got the beautiful cotton dress?" She answered, "No!" "Why not?" he asked. "Well, it was 8 on the window of the shop for a week. So I think 9 wants this dress. So I don't want it, 10 ." | ||||
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