问题 实验题

小明同学欲通过实验证明“二氧化锰是氯酸钾受热分解的催化剂”这一命题,他设计并完成了下表所示的探究实验:

(1)请你帮小明同学填写上表中未填完的空格。

(2)在小明的探究实验中,“实验一”和“实验二”起的作用是                                   

(3)小英同学认为仅由上述实验还不能完全得出表内“总结”,她补充设计了两个方面的探究实验,最终完成了对“命题”的实验证明。第一方面的实验操作中包含了两次称量,其目的是                           ;第二方面的实验是要                                       。

(4)小华在实验室中用老师提供的氯酸钾和二氧化锰的混合物8.0 g为原料制取氧气,加热一段时间后,产生氧气0.075 mol。则:

①分解的氯酸钾的质量是多少?(列式计算)

②根据以上信息,能不能确定原混合物中二氧化锰的质量?如回答“能”,请算出具体质量;如回答“不能”,请说明理由。

答案

(1)

(2)对照实验(或对比)

(3)比较二氧化锰在反应前后质量是否发生改变; 验证回收的二氧化锰是否还有催化作用。

(4)①设:分解的氯酸钾物质的量为xmol

            2KClO32KCl+3O2↑ 

                2                          3

                x                     0.075mol 

            2/3=x/0.075mol 

            x=0.05mol 

            122.5g/mol×0.05mol=6.125g

            答:分解氯酸钾的质量为6.125克

         ②不能,没有足够信息表明原混合物中的氯酸钾已全部分解 

单项选择题
单项选择题

The Lakers’ forward Kobe Bryant has scored 50 or more points in four straight games, second in the NBA only to Wilt Chamberlain’s seven. He also now is tied with Michael Jordan for second with four behind Chamberlain’s 32 in most 60-point games.

"He’s doing something I’ve never seen," Lakers coach Phil Jackson said in an e-mail Saturday. "This has been historic." He should know because he coached Jordan and played against Chamberlain. Bryant is not going to win the MVP award, which likely will go to Dirk Nowitzki or Steve Nash. But his scoring brilliance again seems to answer the question of who’s the best player in the league and it also provides more evidence in the similarity of Bryant and Jordan in their talent and approach to the game.

In any ease, Bryant is the player now firmly holding that mythical torch of greatness, sporting celebrity and creativity that Jordan once took from Julius "Dr. J" Erring. "Kobe has the verdant green light to hoist it up until he cools down," Jackson said. "Wonders never cease in this game." Certainly, Bryant has been wonderful in the four games, averaging 56.3 points with two games of at least 60. Moreover, he hardly has been selfish or working outside the offense because most of his field goals have come on long jumpers, including 17 of 33 on three-pointers. Bryant is shooting 54 percent.

"It’s phenomenal. It’s incredible," Jackson told Los Angeles reporters. "He’s shooting [outside] more than Michael was. Michael was probably doing more post-up, more penetration, more at-the-basket kind of stuff. But Kobe’s doing a whole range of things. I think his shooting has just been remarkable, the way he is raising up over people and knocking the ball down."

It’s still a long way off, but because he started in the NBA when he was 18, Bryant, 28, can pass Kareem Abdul-Jabbar as the league’s all-time scorer if he can stay healthy and average 25 points until he is 38. "The best part of it all is that we’re winning," Bryant said. "The second is that this generation of players who might not have ever heard of the Elgin [Baylors] or Wilts [and their] greatness will now take notice so the legacy of their brilliance will live on.

"As far as myself, I can’t explain it. All is in slow motion all the time. I don’t know why or how, but it’s trippy." That’s probably what Chamberlain said during his record run.

Why is not Bryant going to win MVP()

A. Dirk Nowitzki or Steve Nash have chance to win the MVP award

B. Bryant is the best player in the league from his scoring brilliance

C. Bryant and Jordan have more similarity in basketball

D. Not referred in this passage