问题 单项选择题

某水厂地面水源的总碱度为20mg/L(以CaO计)。三氯化铁(以FeCl2计)投加量为15.4mg/L,剩余碱度取0.4mmol/L(以CaO计)。每天处理水量12000m3,则一天需投石灰( )(市售品纯度为50%)。(已知相对原子质量Fe=55.85,Cl=35.45,Ca=40)

A.440kg
B.220kg
C.250kg
D.125kg

答案

参考答案:C

解析:水源总碱度折合为:20/56=0.357mmol/LFeCl3相对分子质量为162.2,故FeCl3投加量为:15.4/162.2=0.0949mmol/L
根据《考试教材》第1册第170页式(6-11),1mmol/L FeCl3与1.5mmol/L CaO反应:
[CaO]=1.5[a]-[x]+[δ]=1.5×0.0949-0.357+0.4=0.185mmol/L=0.185×56mg/L=10.36mg/L
水厂需投加市售石灰:10.36/0.5=20.72mg/L
水厂每天需投加市售石灰:20.72×12000=248640g=249kg
注意:投加FeCl3与投加Al2(SO4)3时,[a]前面的系数不同。

阅读理解

阅读理解。

                                                             The Statue of Liberty

                                                                  自由女神铜像

     In the water around New York City is a very small island called Liberty Island. On Liberty Island there

is a very special statue called the Statue of Liberty. It is one of the most famous sights in the world.

      The Statue of Liberty was a gift from the people of France to the people of the United States. The statue

was made by a French sculptor (雕塑家) named Frederic Auguste Bartholdi. 1 The inner support system

was designed by Gustave Eiffel, the same man who made the famous Eiffel Tower in Paris.

     Liberty, of course, means freedom, and the Statue of Liberty was given to the United States to celebrate

the one-hundredth anniversary (周年纪念日) of U.S. independence (独立) from England. The statue was

built in France, taken apart piece by piece, and then rebuilt in the United States. 2 It was opened for the

public on October 28, 1886.

     As you might expect, the statue is very big. Visitors can ride an elevator (电梯) from the ground to the

bottom of the statue. If they want to, they can then walk up the 168 steps to reach the head of the statue

where they can look out and enjoy the beautiful sight (景色) of the city of New York.

Find the words in that are closest in meaning to the words or expressions in Column 1.

Column 1                                                                                            Column 2 

( )1. present                                                                                      A) island

( )2. the state of being free                                                                 B) gift

( )3. a piece of land surrounded by water                                            C) freedom

( )4. be in, and be carried in a bus                                                       D) supoort

( )5. bear the weight of                                                                       E) ride 

单项选择题