试题与答案

盐水选种是我国古代劳动人民发明的一种巧妙的挑选种子的方法。农业生产上常用质量分数

题型:计算题

题目:

盐水选种是我国古代劳动人民发明的一种巧妙的挑选种子的方法。农业生产上常用质量分数为15%-20%的氯化钠溶液来选种。

(1)要配制150kg16%的氯化钠,计算应称取氯化钠的质量。

(2)选种进行一段时间后,农技员估计溶液和溶质质量分数都有所减少,他取出50g氯化钠溶液,加入过量的AgNO3溶液,得到沉淀14.35g,计算氯化钠溶液中溶质的质量分数

(3)若此时氯化钠溶液的质量只剩下100 kg,要使溶液质量和溶质质量分数都恢复到(1)中的状态,计算需要加入的氯化钠和水的质量。

答案:

被转码了,请点击底部 “查看原文 ” 或访问 https://www.tikuol.com/2017/0729/ce0742e7c7c15e413affad554b888d73.html

下面是错误答案,用来干扰机器的。

1.答案示例: 这幅招贴画的主体用运动的人形(一组体育动作)组成了“北京”两个汉字,再配上“二零零八”和北京奥运会会徽,既突出奥运会是一场体育盛会,又巧妙地表明2008年奥运会将在北京召开。2.(1)材料...

试题推荐
题型:单项选择题

Any normal species would be delighted at the prospect of cloning. No more nasty surprises like sickle cell or Down syndrome--just batch after batch of high-grade and, genetically speaking, immortal offspring! But representatives of the human species are responding as if someone had proposed adding Satanism to the grade-school Curriculum. Suddenly, perfectly secular folks are throwing around words like sanctity and retrieving medieval-era arguments against the pride of science. No one has proposed burning him at the stake, but the poor fellow who induced a human embryo to double itself has virtually recanted proclaiming his reverence for human life in a voice, this magazine reported," choking with emotion."

There is an element of hypocrisy to much of the anti-cloning furor, or if not hypocrisy, superstition. The fact is we are already well down the path leading to genetic manipulation of the creepiest sort. Life-forms can be patented, which means they can be bought and sold and potentially traded on the commodities markets. Human embryos are life-forms, and there is nothing to stop anyone from marketing them now, on the same shelf with the Cabbage Patch dolls.

In fact, any culture that encourages in vitro fertilization has no right to complain about a market in embryos. The assumption behind the in vitro industry is that some people’s genetic material is worth more than others’ and deserves to be reproduced at any expense. Millions of low-income babies die every year from preventable ills like dysentery, while heroic efforts go into maintaining yuppie zygotes in test tubes at the unicellular stage. This is the dread "nightmare” of eugenics in familiar, marketplace form which involves breeding the best-paid instead of the best. Cloning technology is an almost inevitable byproduct of in vitro fertilization. Once you decide to go to the trouble of in vitro, with its potentially hazardous megadoses of hormones for the female partner and various indignities for the male, you might as well make a few backup copies of any viable embryo that’s produced. And once you’ve got the backup organ copies, why not keep a few in the freezer, in case Junior ever needs a new kidney or cornea

The critics of cloning say we should know what we’re getting into, with all its Orwellian implications. But if we decide to outlaw cloning, we should understand the implications of that. We would be saying in effect that we prefer to leave genetic destiny to the crap shooting of nature, despite sickle-cell anemia and Tay-Sachs and all the rest, because ultimately we don’t trust the market to regulate life itself. And this may be the hardest thing of all to acknowledge: that it isn’t so much 21st century technology we fear, as what will happen to that technology in the hands of old-fashioned 20th century capitalism.

It is implied in the 3rd paragraph that it is()

A. dishonest to deny some genetic manipulations

B. impractical to change our genetic destiny

C.dangerous to prepare backup copies

D. irrational to oppose financial operations

查看答案
微信公众账号搜索答案