题干

下列有关实验操作的分析中,正确的是(  )

A:取用稀硫酸:取出一部分溶液后,导致浓度降低

B:配制氯化钠溶液:量取水时,仰视读数,导致浓度偏大

C:测定空气中氧气含量:未冷却至室温即可打开弹簧夹,导致进水偏少

D:去除粗盐中难溶性杂质:将粗盐全部加入水中,立即过滤,导致产率偏高

上一题 下一题 0.0难度 选择题 更新时间:2017-10-21 11:26:49

答案(点此获取答案解析)

C

同类题4

阅读A篇短文,从每小题所给的四个选项中,选出能回答所提问题或完成所给句子的最佳答案,并将答题卡上对应的选项涂黑.

    Welcome to the Painting Competition for Woolands Students.

The International Anti﹣Drug Day this year is coming soon. In order to raise teenagers awareness to fight against drug taking. The seat on the council is going to hold a painting competition for the students in our city.

    Students who want to take part in the competition can hand in their own 2D paintings in either of the following two ways:

Each school will be provided with a box for students to put in their paintings. Boxes will be picked up by the City Art Council on Thursday, July 23rd, 2016, before the end of the school day.

    Paintings can be also handed in on Friday, July 24th, from 8: 00am to 10: 00am at the Woodlands Art Hall.

    Or paintings are required to be, 60cm wide by, 80cm long, or smaller. Larger sizes of you not be accept. Each student can only hand in one painting.

The final decision on the competition results will be made on June 26th, the Anti﹣Drug Day. The name list of the winners will be made known on the website of the City Art Council on the same day. All women paintings will be shown to the public at the City Youth Park from June 27th till the end of July.

Prize: 1st Prize(10students)=﹩300GiftCardeach.

2ndPrize(20students)=﹩200Gift Card each.

3rd Prize(30students)=﹩100Gift Card each.

For further information: Visithttp://www. woodlandsartcouncil. org. cn

call 2569﹣8632.