题干

室温下,VaLpH=a的强酸与VbLpH=b的强碱溶液混合,混合后溶液pH=3。已知a+b=13,Vb=4.5Va ,则a值为                          

A:2

B:3

C:4

D:5

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A

同类题2

阅读理解

    On the morning of May 20, 1927, Charles A. Lindbergh Jr. took off from a muddy airfield in New York and headed for Paris. During the first fourteen hours of flying, he had had some anxious moments. Sleet had gathered on the wings of the plane and the fog was so thick that he could hardly see the tips of the wings. However, he had come across equally dangerous flying conditions before. Of course, now that he was over the ocean, his parachute(降落伞)was useless. He had only one choice: he had to go on.

    Although he had waited a long time to make this trip, he did not feel strange or nervous. He was accustomed to flying alone, and he had flown this route in his imagination many times. The idea of flying across the Atlantic had occurred to him one night when he had been carrying the mail between St. Louis and Chicago. That night, he told himself that a solo non-stop flight between New York and Paris was possible. He knew that airplanes capable of making the long flight over the ocean could be built. A man of skill and endurance could make his dream come true.

    As he was recalling that night, he reduced the altitude of the plane. Close to the surface of the ocean, he found that the ice on the wings began to melt and the fog disappeared. For the time being, at least, he was safe. The steady sound of the motor seemed like music in his ears. He had perfect confidence in his plane because he knew that there was not a more dependable plane than his. The Ryan Aircraft Company had constructed the plane to meet his special needs. He had worked with the chief engineer of the company, Donald Hall, to produce the airplane as rapidly as possible. Although Hall had worked with the basic design of the Ryan airplane, he had had to make many modifications. As a result, it was a very special airplane. He had named it “The Spirit of St. Louis,” in honour of the St. Louis businessmen whose financial backing had made the trip possible. Besides their money, he had invested all of his own savings, which came to two thousand dollars, in the venture.

    At 12:10 on the afternoon of May 21, Lindbergh caught sight of the coast of Ireland. Now that the flight was almost over, he began to relax a little. Finally, after thirty-four hours in the air without sleep, he arrived at Le Bourget Field, in Paris.

同类题3

阅读下面短文,从短文后面各题所给的四个选项(A、B、C和D中,选出可以填入空白处的最佳选项。

    The cultures of the East and the West really distinguish from each other a lot. This is because the culture systems are two 1 systems on the whole.

    The origin of the eastern culture is mainly from two countries: China and India. Both of the two cultures are gestated(孕育) by 2. In China, the mother river is the Yellow River, 3 the Indian one is the Hindu River. These two cultures have 4 for several thousand years and formed their own styles. Then in Tang Dynasty of China, the Chinese culture 5 went overseas to Japan, 6 into the Japanese society and 7 the Japanese culture nowadays. Though a bit different from the Chinese one, it 8 to the same cultural system.

    When the two mother rivers gave birth to the eastern culture, another famous culture was 9 on the Mesopotamian Plain(米索不达米亚平原): the Mesopotamian Civilization. This civilization later on developed into the cultures of the Ancient Greece and Ancient Rome. And these two are well-known as the 10 of the European culture. 11 the Chinese culture, the European one is also 12 to waters. When the colonists(殖民者) of England 13 in America, their culture went with them over the Atlantic Ocean. So the American culture doesn't 14 from the European one a lot.

    At the same time, the 15 of the language systems adds to the cultural differences. In the East, most languages belong to the pictographic(象形文字的) languages while the Western languages are 16 based on the Latin system, for example, the one I'm using to write this paper.

    Other factors like human race difference counts 17 . However, 18 the far distance and the steep areas between the East and West, the two cultures seldom 19 until recent centuries. 20 they grew up totally in their own ways with almost no interference from the other.