A solution of which substance can best be used as both a titrant and its own indicator in an oxidati
(a) I2(b) NaOCl (c) K2Cr2O7(d) KMnO4
(a) I2(b) NaOCl (c) K2Cr2O7(d) KMnO4
Compute [OH-] and [H+] in a 0.10 M solution of a weak monoprotic base which is 1.30% ionized. What is the pH of the solution?
Will MnS be precipitated from a saturated solution of H2S(0. 10M) which is maintained at pH=5.00 by a buffer,if the concentration of Mn2+ini tially present is 0. 010M?
Which paragraph offers a possible solution for brain drain?
A.Paragraph 1.
B.Paragraph 2.
C.Paragraph 3.
D.Paragraph 4.
A.patches B.compensations C.complements D.additions
Which is not stated as the feature of expert systems?
A.Expert systems can always reason with metaknowledge.
B.Expert systems use knowledge rather than data to control the solution process.
C.Expert systems can explain how a particular conclusion is reached.
D.Expert systems use symbolic representations for knowledge.
An iron bar is to be electroplated with zinc.
·Identify what will act as the two electrodes for the cell
·Identify each electrode as either the anode or cathode
·Write the half- reactions occurring at each electrode
·Identify a solution that would make a suitable electrolyte for this cell
·Identify which electrode will be attached to the negative post of the battery and which will be attached to the positive post, and explain.
What is the main subject of the passage?
A.A solution to man"s food problem.
B.A solution to the population problem.
C.Advantages of soybean.
D.How to develop good eating habits.
根据下面内容,回答题:
Many of the problems we face today are not so new as we think they are. And some of our modern solutions are not so new, either. The problem of energy shortages and the solution of using solar energy go back at least to early Greek cultures. The climate in the coastal areas of Greece 2,500 years ago was characterized by cool winters, much as it is today. At that time, the Greeks heated their homes with small, charcoal-burning heaters. In other words, wood (which is used to make charcoal) was their primary source of energy.However, by the fifth century BC fuel shortages had become common because, in many parts of Greece, the firewood in the forests had been depleted. Once the supply of firewood from the local forests ran out, people began to use the wood from olive groves as fuel. But this solution had its own problem. It reduced the olive crop, a valuable resource to the Greeks. By the fourth century BC, the city of Athens banned the use of olive wood for fuel. Wood had to be imported from farther and farther away, making it more difficult to obtain and more expensive to use. About this time the Greeks began to build their houses facing south, so that the low sun in winter could penetrate and help heat the interiors. Excavations of ancient Greek cities suggest that large areas were planned so that individual homes could take maximum advantage of passive solar energy.
The word "depleted" means________. 查看材料
A.damaged
B.stolen
C.used up
D.discovered
The farmers are reported to have difficulty in______.
A.hiring harvest workers
B.selecting the right fruit to grow
C.selling their farm produce
D.changing their way of farming