试题与答案

精密量取维生素C注射液4ml(2ml:0.1g),加水15ml与丙酮2ml,摇匀,放

题型:单项选择题 A1/A2型题

题目:

精密量取维生素C注射液4ml(2ml:0.1g),加水15ml与丙酮2ml,摇匀,放置5分钟,加稀醋酸4ml与淀粉指示液1ml,用碘滴定液(0.05mol/L)滴定,至溶液显蓝色并持续30秒钟不褪。每1ml碘滴定液(0.05mol/L)相当于8.806mg的维生素C(CHO)。消耗的碘滴定液(0.05mol/L)的体积和浓度分别是10.90ml和0.0506mol/L。根据上述实验,判断正确的是()

A.本实验利用了维生素C具有很强的氧化性

B.本实验维生素C注射液的含量95.98%

C.本实验维生素C注射液的含量97.13%

D.滴定终点溶液显紫色

E.本实验维生素C注射液的含量97.14%

答案:

参考答案:E

解析:

利用维生素C具有很强的还原性,在稀醋酸的酸性条件下,以淀粉为指示剂,用0. 05mol/L碘滴定液直接滴定,滴定至溶液显蓝色为终点。根据消耗的碘滴定液(0. 05mol/L)的体积和浓度,计算维生素C注射液的含量。V代表消耗滴定液ml数;C代表滴定液的实际浓度;标示量代表每支注射液中维生素C的克数。本实验维生素C注射液的规格为2ml:0.1g,表示每支容量为2ml,标示量为0. 05g。计算公式如下:维生素C注射液标示量%=

试题推荐
题型:不定项选择

犯罪嫌疑人陈某与尚某是合法的夫妻,被害人刘某是尚某的外甥,刘某常年在国外工作,1999年回国探亲,一日在其姨尚某家留宿,陈某游手好闲,没有固定工作。看见刘某出手阔绰,心存歹意,恰巧刘某住他家中,于是想说服尚某与其一同偷窃刘某的钱物,尚某不同意,陈某便威胁尚某,如果尚某不同意,陈某就会不仅偷,还会加害于刘某。于是尚某被迫帮助陈某在刘某熟睡以后盗窃其钱物,但尚某只是帮助打看刘某是否睡着,察看刘某的钱物放在哪,陈某在盗窃的过程中,被刘某觉察,陈某见事情败露,拿起旁边桌子上的钟表朝刘某头部砸去,刘某当场死亡。案发后,县公安局经县检察院批准,将陈、尚二人逮捕。公安机关侦查终结后案件事实清楚,证据确实充分。于是将尚、陈二人移送县检察院提起公诉。人民检察院决定不起诉的案件,以下做法正确的有( )。

A.人民检察院可以根据案件的不同情况,对被不起诉人予以训诫或者责令具结悔过、赔礼道歉、赔偿损失

B.对被不起诉人需要给与行政处罚、行政处分或者需要没收其违法所得的,人民检察院应当提出检查意见,连同不起诉决定书一并移送有关主管机关处理

C.不起诉的决定应当公开宣布

D.如果被不起诉人在押,必须经过复议期限、申诉期限方可释放

查看答案
题型:单项选择题

The Federal Government


联邦政府


The Constitution
When America broke away from Britain in 1775, she did not adopt a British Constitution. The British have always had an unwritten constitution, whereas every item of the American Constitution is clearly written down and numbered, and can only be changed by a two-thirds majority vote of Congress.
Yet in their different ways, the American and British forms of government did have one thing in common. They were both democratiC.As for American society, it was more democratic than British society, in that it paid less attention to class or wealth.
Political Parties
There are two major political parties in the USA, the Democratic Party and the Republican Party. The policies of the two parties are not basically opposed to one another. Inside both parties there moderates and right-wringers, though the Democrats still have the reputation of being somewhat more liberal than the Republicans. Voters are influenced by family traditions, but there are plenty of ordinary people who vote according to their hopes, fears and beliefs.
There are no other political parties that can compete with the two big parties, though there are occasionally independents who stand for the presidency and manage to collect quite a few votes. There are no left-wing parties. Most Americans are in favor of free enterprise, believing that it may one day help them fulfill the American Dream.
The President and Congress
The President of the USA has more power than any other president in the democratic world- except the French President. It is he who formulates foreign policy and prepares laws for the home front. He is leader of the nation and Commander-in-Chief of the Armed Forces. He represents the USA and, since the USA is a super power, the eyes of the whole world are on him. The fate of the world is in his hands, or so many people believe, and one careless, ill-prepared speech by him could precipitate a crises.
Actually, a great deal of the President’s power is controlled by Congress, the American name for "parliament". It is Congress that declares war, not the President. Unlike the Prime Minister of Great Britain, or of Germany, he can make a treaty with a foreign power. But this treaty must be debated and agreed by Congress before it comes into force. The same control applies to laws at home. Congress has (on several occasions) refused to ratify treaties or given approval to laws proposed by the President. The USA is the only country, apart from France, where a president can rule with a parliament, the majority of whose members do not belong to his own political party.
Some Americans have the feeling that idealism has gone out of politics and that personal ambition and money have taken its place. The election campaign fro the Presidency is unique in the amount of money poured into it. The wooing of voters lasts for months. But before the campaign for the election of the President can begin, each political party has to choose its candidate for the Presidency. This can lead to some very close contests. Men aspiring to be elected as the party candidate employ top public relations and advertising men, who invent clever catch phrases and set about "selling" their man. There are whistle stop tours by train, by plane, by car. The candidate delivers countless speeches and shakes countless hands. This razzamatazz typifies American enthusiasm and extravagance.
Big money is necessary to support a presidential candidate’s campaign and the candidate himself must be rich enough to pay his share. An attractive wife is an advantage, too. Money is also needed to become the Governor of a state, or a successful Senator, or member of the House of Representatives. Yet from this small group many excellent men have become President, and the same is true of members of Congress.
It is very unlikely that the President could ever become a dictator. Congress, the press and the people between them rule out such a possibility.
The Supreme Court
Perhaps the most effective safeguard of democracy is the Supreme Court, for one of its objects is to protect the individual against the government. It has the authority to cancel a law which it considers violates the Constitution. The Court sits for at least four days a week and any individual who has a grievance against the government can apply to it for help.
The Supreme Court goes way back to 1787, the days of the Founding Fathers, and is one of the cornerstones of American democracy. It gives judgement in disputes between States, or between a State and the Federal Government, and without invitation can declare a law made by Congress to be unconstitutional. The great Jefferson, who drew up the Declaration of Independence, saw to it, too, that there was a Bill of Rights which every American could thrust under the nose of anyone who tries to rob him of his freedom as a democratic citizen.

Every item of the American constitution is______.

A.not numbered
B.not written down
C.challenged by a 2/3 majority of Congress
D.clearly written down and numbered

查看答案
微信公众账号搜索答案