先化简后求值:(1+1a-1)÷(aa2-1-aa+1),其中a=14.

题型:解答题

问题:

先化简后求值:(1+
1
a-1
)÷(
a
a2-1
-
a
a+1
),其中a=
1
4
考点:分式的加减乘除混合运算及分式的化简
题型:解答题

为了防止枪支生锈,常将枪支的钢铁零件放在NaNO2和NaOH的混合液中进行化学处理经处理后钢铁零件表面生成Fe3SO4的致密的保护层——“发蓝”。主要反应如①②③:

①3Fe+NaNO2+5NaOH→3NaFeO2+NH3+H2O

②___Na2FeO2+____NaNO2+____H2O→   Na2Fe2O4+    NH3+    NaOH

③Na2FeO2+Na2Fe2O4+2H2OFe3O4+4NaOH

(1)配平化学方程式②,标出电子转移方向和数目。

(2)上述反应②中还原剂为           ,被还原物质是____      

若有1mol Na2Fe2O4生成,则反应中有____mol电子转移。

(3)当NaOH溶液浓度过大,“发蓝”的厚度会变小,其原因是:        

题型:解答题

某人误食某种物质1小时候后,出现头晕、头痛、恶心、呕吐、多汗、胸闷、视力模糊、无力、肌震颤、瞳孔缩小、呼吸困难、意识模糊、呼出气体有大蒜样恶臭,该人可能是()

A.有机磷农药中毒

B.有机氯农药中毒

C.亚硝酸盐中毒

D.含砷杀虫剂中毒

E.毒蕈中毒

题型:解答题

小儿麻痹初期邪气侵犯的脏腑是()

A.肝肾

B.心肺

C.脾肾

D.肺胃

E.心肝

题型:解答题

如图所示,是某次同步卫星发射过程的示意图,先将卫星送入一个近地圆轨道,然后在P点点火加速,进入椭圆转移轨道,其中P是近地点,Q是远地点,在Q点再次点火加速进入同步轨道.设卫星在近地圆轨道的运行速率为v1,加速度大小为a1;在P点短时间点火加速之后,速率为v2,加速度大小为a2;沿转移轨道刚到达Q点速率为v3,加速度大小为a3;在Q点点火加速之后进入圆轨道,速率为v4,加速度大小为a4,则(   )

A.

B.

C.

D.

题型:解答题

Egyptian wine has an extensive history within the history of Egyptian civilization. Grapes were not (1) to the landscape of Egypt, rather the vines themselves are (2) to have been imported from the Phoenicians, (3) the actual origins remain in (4) . What is known, is that (5) the third millennium BC, Egyptian kings of the first (6) had extensive wine cellars, and wine was used extensively in the temple ceremonies. The main (7) of wine in Egypt, took place between the king, nobles, and the priests in temple ceremonies, and is (8) by numerous painted relief’s, and other (9) evidence. The vineyards of ancient Egypt, were quite different from the modern methods of wine making today. (10) viticulture ( or wine making), ceased to (11) an exclusively ceremonial purpose, the Egyptians began to experiment with simple structures for their vines to train on, (12) found a way to train their vines so they were easy low (13) bushes, and found ways for the soil to (14) more moisture for the vines. Egyptian wine making experiments included the use of different wine presses, adding heat to the must ( the grape juice ready for fermentation) (15) make the wine sweet, and differences in vat types and materials. The (16) finished product of wine, was poured through a cloth filter, and then into earthenware jars, (17) they would be sealed with natural tar and left to (18) . The Egyptians kept accurate records of their vintages, and (19) of their wines, each jar of wine was clearly (20) with it’s own vintage, and quality.

20()

A.marked

B.written

C.labeled

D.recorded

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