化学老师交给九年级某研究性学习小组一个任务:测定实验室一瓶久置的NaOH固体是否

题型:实验题

问题:

化学老师交给九年级某研究性学习小组一个任务:测定实验室一瓶久置的NaOH固体是否变质。该小组同学进行了如下实验探究:

【猜想】猜想Ⅰ:没有变质;猜想Ⅱ:全部变质;猜想Ⅲ:部分变质

【查阅资料】部分盐溶液在常温下的pH如下表所示:

【设计方案,并进行验证】请你与他们一起探究,并回答下列问题:

上述步骤(1)中滴加过量BaCl2溶液的目的是________。

【实验结论】通过实验,说明上述猜想中_________是正确的。

【拓展】该小组同学为了测定出该NaOH固体的变质程度,继续将步骤(1)静置后的混合物过滤,将白色沉淀洗涤、干燥,称得其质量为3.94g,则原样品中NaOH的质量分数为____ (假定试剂中无杂质)。

【反思】久置的NaOH变质的原因是________。

考点:设计实验和科学探究物质的变质
题型:实验题

在结构化程序设计思想提出之前,在程序设计中曾强调程序的效率。与程序的效率相比,人们更重视程序的( )。

A.安全性

B.一致性

C.可理解性

D.合理性

题型:实验题

指数化型证券组合只是一种模拟证券市场组合的证券组合。(  )

题型:实验题

信息匹配。

阅读下列应用文相关信息,并按照要求匹配信息。

以下是一些生活感想或经验介绍:

A. More than nine years ago I was 70 pounds overweight and wore a very big dress. I had tried different diets and lost weight only to gain it back. Finally a simple "threeforone"fat rule worked for me: consuming

no more than three grams of fat for every 100 calories per serving. Following the rule and eating only

foods that contain less than 30 percent fat, I spent eight months getting down to a size seven, and I've

kept the weight off for nine years.

B. And for foods that aren't packaged, you rely on what we already know about them. Red meat,as well

as dishes made or served with butter, gravy, cream, sauce or cheese, are almost never less than 30 percent fat, so you just don't eat them. On the other hand, some nonpacked foods-all fruits and vegetables except avocadoes and olives-always pass the test. So do most fish, but not when fried.

C. I like vegetables, which are rich in vitamins. Most foods containing vitamins C and E (such as sweet

potatoes, tomatoes, spinach and broccoli) are low in calories and are known as antioxidants(抗氧化物质). They can help reduce the possibility to develop hardening the arteries(动脉).

D. I gain weight around the belly-what we call abdominal obesity, the worst kind. The tendency seems to

be hereditary (遗传的), and it's common among men. This problem increases the risk of a stroke or heart attack. A guide I use in estimating belly fat is the waisttohip ratio or WHR. To find yours, divide the

circumference (圆周) of your waist by the circumference of you hips. Women with ratios above 0.8 and

men with ratios above 1.0 are at increased health risk.

E. My ways of keeping healthy are very simple, and they are among our everyday activities: eating healthy

food and doing exercise. In addition, I manage to do those basic things, such as drinking water, sleeping

well and eating less fat. Sometimes I do some of the other things I used to do in my life like walking for

half an hour a day.

F.Although I've put on ten pounds, I'm healthy and in good shape. I eat food that's good for me…but I

work off Susan's homemade brownies (巧克力蛋糕), for example, to offset these extra calories, I walk

for an hour or more, three times a week…often with Susan. We're both busy and this is one way we have some quiet time together. Equally important, it permits me to practice dieting's fine art of compromise.

以下是五位专家的建议.请匹配这些建议及对应的生活感想或经验介绍(A、B、C、D、E和F).

1. You should watch where your weight accumulates. You can use the waist to hip ratio to find if there is

    too much fat around the middle. Belly fat is especially dangerous because it releases free fatty acids

    directly to the liver, virtually flooding it with fat.

2. If a particular food is important to you, eat it, but work it off. You should try to learn the art of

    compromise.

3. At the same time. the threeforone is relatively simple to use. Fat grams and calories are listed on

    almost all boxed, canned or packaged foods. You have only to read the label and follow the rule.

     A fiveyearold patient of mine can do this.

4. Drinking water is basic, and drinking enough of it is necessary. Patients are sometimes surprised that

    basic things work when they do them consistently.

5. Consume antioxidant foods. They protect the cholesterol(胆固醇) from oxidative damage,which

    helps prevent damage to blood vessel walls.

题型:实验题

高温下14CO2与碳发生反应:14CO2+C2CO达到平衡后,平衡混合物中含14C的粒子有                                                           

A.14CO214CO14C

B.14CO214CO

C.14CO2

D.14CO

题型:实验题

哺乳动物的卵细胞比精子大得多,其生物学意义是()

A.有利于受精作用

B.有利于减数分裂

C.有利于胚后发育

D.有利于胚胎发育

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