题干

下列叙述不正确的是(  )

A:钾、钠、镁等活泼金属着火时,不能用泡沫灭火器灭火

B:探究温度对硫代硫酸钠与硫酸反应速率的影响时,若先将两种溶液混合并计时,再用水浴加热至设定温度,则测得的反应速率偏高

C:蒸馏完毕后,应先停止加热,待装置冷却后,停止通水,再拆卸蒸馏装置

D:为准确配制一定物质的量浓度的溶液,定容过程中向容量瓶内加蒸馏水至接近刻度线时,改用滴管加蒸馏水至刻度线

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答案(点此获取答案解析)

B

同类题1

阅读下面短文,从短文后各题所给的四个选项(A、B、C和D)中,选出可以填入空白处的最佳选项。

    One rainy afternoon I was sitting at home feeling so bored.1 feeling sorry for myself, I wanted to meet people and have new2, so I decided to start volunteering. I found a website where I could volunteer on a farm in France.

    Volunteering 3 so many opportunities to have fun and share 4stories. It was the first time for me to work on a farm. It was almost a(n)5holiday as food and accommodation were provided. It was not one6 holiday, however, as I had to 7 fifteen horses and sheep! I soon discovered that I was a(n) 8 farmer but it did not matter because I made some great friends and also improved my9.

    However, you do not 10 go abroad to volunteer. I have had plenty of adventures at home as volunteering can become a11. For example, I love12 so I had a good laugh waving my arms in order to 13my local choir(合唱团). At university, I organized a concert for charity with my friends. It was really 14 to find bands and raise money for a cause.

    It is true that you feel good volunteering but there are also other 15.I once volunteered as a steward (干事) at a charity sports event where the organizers 16 gave me cupcakes from an expensive London bakery to thank me for my 17. I also volunteered in a charity shop so I found loads of nice cheap clothes to 18my wardrobe(衣橱).

    While this is all fun, my favourite aspect of volunteering is 19and sharing stories. My terrible20  at farming has given me funny stories to tell!