问题 填空题

下列物质都可用于自来水的净化.

1)高铁酸钾(化学式K2FeO4)集氧化、吸附、凝聚、杀菌功能于一体,目前被广泛应用于自来水净化处理领域.高铁酸钾中铁元素的化合价为______.

2)漂白粉可用于水的杀菌消毒,其有效成分是次氯酸钙[化学式为Ca(ClO)2].次氯酸钙可发生如下反应:Ca(ClO)2+CO2+X=CaCO3↓+2HClO,则X的化学式______.

答案

(1)钾元素显+1价,氧元素显-2价,设铁元素的化合价是x,根据在化合物中正负化合价代数和为零,可得:(+1)×2+x+(-2)×4=0,则x=+6价.

(2)根据反应的化学方程式Ca(ClO)2+CO2+X=CaCO3↓+2HClO,反应物中钙、氯、碳、氧原子个数分别为1、2、1、4,反应后的生成物中钙、氯、碳、氧、氢原子个数分别为1、2、1、5、2,根据反应前后原子种类、数目不变,则每个X分子由2个氢原子和1个氧原子构成,则物质X的化学式为H2O.

故答案为:(1)+6;(2)H2O.

单项选择题
阅读理解

Jockeys(职业赛马骑师) are the smallest athletes. They are rarely over five feet six, or 120 pounds. The lighter the weight on the horse, the faster it can go.

Riding fast horses on the track is tough on the small jockeys. The jockey doesn’t“sit”on the horse. He leans forward on his legs. The strain is on his thighs(大腿) and calf(小腿) muscles. As jockeys age, their legs“go”first. Jockeys also need arm strength. It’s a strain holding a 1000-pound racehorse.

On muddy days, jockeys get a pounding of mud. The mud comes flying off the hooves(蹄) of the horses in front. “It feels like someone is punching you all over,”says one rider.

And a jockey can be hurt. A jockey can have a leg jammed between two horses. Or it can get caught between horse and the rail. The worst accidents are from falls. A horse may fall on his rider. Or horses behind may trample if he hits the track. In one year about 240 riders are hurt badly. That’s one out of six jockeys.

But the jockeys are well-paid. A jockey keeps about ten percent of the money his horses win. Jacinto Vasquez, a five-foot-three comer, has ridden horses to $7,000,000 in wins in the last eight years, which means he does almost $100,000 a year.

Why do some jockeys do better than others? “It isn’t the way a boy sits on a horse or uses the reins or the whip,”says Conn McCreary. McCreary was a top jockey of the 1950’s. He rode two Kentucky Derby winners. “Most jockeys do this the same. It’s the ‘feel’ he has for the horses.”

“When you come right down to it, it just seems that horses run better for some riders,” McCreary says. “A real good jockey doesn’t lose with the best horse. And sometimes he’ll win with the second or third best.”

Many Latin-American riders, like Jacinto, seem to have the knack. “Maybe it’s because we grew up with horses,”says Jacinto. “Maybe it’s because we like to ride. There was a strike at Aqueduct last year. We, Jorge Velasquez, and Angel Cordero (two other top Latin riders) went to a park. We rented horses, and rode around the bridle path(骑马专用道)!”

小题1:The main idea of Paragraph 1 is about ______________.

A.the size of jockeys.

B.the age of jockeys

C.the size of the horse

D.the speed of the horse小题2:When a jockey is riding a fast horse, he doesn’t __________.

A.really sit on the horse

B.lean forward on his legs

C.use much arm strength

D.get any mud on wet track小题3: The most dangerous problem for a jockey arises __________________.

A.when his leg is jammed between two horses

B.when his clothes are splashed over with mud.

C.when the jockey’s horse falls on the jockey

D.when the jockey is not well paid小题4:A really good jockey can often win a race ____________.

A.only when he rides on the best horse

B.even when he rides the second best horse

C.when he rides on a rented horse

D.if the horse is just a Kentucky Herby小题5: The underlined word “Knack” in the last paragraph probably means__________________.

A.special skill

B.dangerous hobby

C.riding culture

D.excellent horses.