用重铬酸钾标定硫代硫酸钠时,重铬酸钾与碘化钾反应时溶液的pH值()。 A.为碱性 B

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问题:

用重铬酸钾标定硫代硫酸钠时,重铬酸钾与碘化钾反应时溶液的pH值()。

A.为碱性

B.为强碱性

C.为强酸性

D.为中性或弱酸性

考点:化学分析工考试化学分析工综合练习化学分析工综合练习题库
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有关苯丙酮尿症(PKU),叙述错误的是()

A.是一种常见的遗传性氨基酸代谢病

B.属常染色体显性遗传病,未经治疗的PKU患儿由于体内蓄积过量的苯丙氨酸及其代谢产物,对神经产生毒性作用,最终出现严重的智能障碍。

C.是由于编码苯丙氨酸羟化酶的基因发生突变,致使PAH活性降低或丧失,苯丙氨酸代谢异常所致

D.中国人群PAH基因突变近30余种

E.可以利用PAH基因中短串联重复序列(如内含子3内TCTAn)扩增片段长度多态性进行连锁分析,产前诊断PKU

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下列关于病室温、湿度描述错误的是

A.一般病室的温度应保持在20~22℃
B.婴儿室、产房的温度应保持在22~24℃
C.病室的湿度应保持在40%~50%
D.病室湿度过高不利于心肾疾病患者
E.病室湿度过低不利于气管切开病人

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雌性菌变为雄性菌是通过()

A.转化

B.局限性转导

C.接合

D.普遍性转导

E.溶原性转换

题型:单项选择题

美国的中央银行制度属于()

A.单一型

B.复合型

C.跨国型

D.准中央银行型

题型:单项选择题

Drug use is rising dramatically among the nation’s youth after a decade of decline. From 1993 to 1994, marijuana use among young people (1) from 12 to 17 jumped 50 percent. One in five high school seniors (2) marijuana daily. Monitoring the Future, which (3) student drug use annually, reports that negative attitudes about drugs have declined for the fourth year in a row. (4) young people see great risk in using drugs. Mood-altering pharmaceutical drugs are (5) new popularity among young people. Ritalin, (6) as a diet pill in the 1970s and now used to (7) hyperactive children, has become a (8) drug on college campuses. A central nervous system (9) , Ritalin can cause strokes, hypertension, and seizures. Rohypnol, produced in Europe as a (10) tranquilizer, lowers inhibitions and suppresses short-term memory, which has led to some women being raped by men they are going out with. (11) taken with alcohol, its effects are greatly (12) . Rock singer Kurt Cobain collapsed from an (13) of Rohypnol and champagne a month before he committed (14) in 1994. In Florida and Texas, Rohypnol has become widely abused among teens, who see the drug as a less expensive (15) for marijuana and LSD. Alcohol and tobacco use is increasing among teenagers, (16) younger adolescents. Each year, more than one million teens become regular smokers, (17) they cannot legally purchase tobacco. By 12th grade, one in three students smokes. In 1995, one in five 14-year-olds reported smoking regularly, a 33 percent jump (18) 1991. Drinking among 14-year-olds climbed 50 percent from 1992 to 1994, and all teens reported substantial increases in (19) drinking. In 1995, one in five 10th graders reported having been drunk in the past 30 days. Two-thirds of high school seniors say they know a (20) with a drinking problem.

12()

A.enlarged

B.confirmed

C.exaggerated

D.magnified

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