问题 选择题

NA为阿伏加德罗常数的值。下列叙述正确的是(  )

A.1.0 L 1.0 mol·L-1的NaAlO2水溶液中含有的氧原子数为2NA

B.1 mol醋酸的质量与NA个醋酸分子的质量一定相等

C.2.24 L CO2中含有的原子数为0.3 NA

D.0.1mol/L 的NaCl溶液中,离子总数为0.2NA

答案

答案:B

题目分析:A、H2O中也含有O原子,错误;B、NA个醋酸分字就是1mol,所以质量一定相等,正确;C、没有注明标准状况,错误;D、没有注明体积,无法计算,错误。

默写题
阅读理解

Talk about a real-life hero! Ten-year-old Larry Champagne from St. Louis, Missouri, hit the brake (刹车) on a runaway school bus. He saved himself and 20 other kids on board from disaster.

It all happened in one terrible accident. On the way to school, the bus driver, Ernestine Blackman, suddenly fell ill. Seeing the car was running away, the other kids started to scream, but Larry ran to the front and stopped the bus.

“At first I thought, ‘We’re going to die,’” says Larry, “but after I pressed the brake, I felt safe.”

Larry’s speedy reaction made news all over the country. He appeared on TV shows as a hero. The bus company gave Larry a big gift. His school hung a medal of honor around his neck.

“My grandmother always tells me to do what’s right,” says Larry. He thanked his brother, Jerrick, 9, who “helped me get the bus driver up” during the emergency. How did he know how to stop the bus? Larry is something of a mechanic(机械师). He helps his grandfather work on his old truck. “He gets his hands dirty,” says his grandfather. One thing is for certain: Larry knows where to find the brakes.

小题1:What did Larry do to save the runaway bus?

A.He parked it for the sleeping bus driver.

B.He helped all the kids climb out through the windows.

C.He made a call to the police.

D.He pressed the brake.小题2:When did Larry finally feel safe?

A.When the kids finally stopped screaming.

B.When the police officers arrived.

C.Once he pressed the brake, and the bus stopped.

D.When the bus driver started driving again.小题3:Larry got the following as praise for his hero action Except _______.

A.appearing on TV shows

B.a scholarship from his school

C.a big gift from the bus company

D.a medal of honor小题4:Larry thanked his brother Jerrick for ________.

A.helping him get the bus driver up

B.helping him work on his old truck

C.teaching him how to find the brake

D.teaching him how to stop the bus小题5:The underlined sentence “Larry is something of a mechanic” tells us that ____.

A.Larry’s job is a mechanic

B.Larry knows something about machines

C.Larry is a robot

D.Larry knows nothing about machines