题干

如图所示是由地面同一点踢出的足球的三条飞行路径,三条路径的最高点是等高的.忽略空气对飞行的影响,下列说法正确的是(   )

A:沿路径1飞行的足球落地速率最大

B:沿路径3飞行的足球的初速度的水平分量最大

C:沿路径3飞行的足球运动的时间最长

D:沿各路径飞行的足球的初速度的竖直分量相同

上一题 下一题 0.0难度 选择题 更新时间:2017-11-29 08:31:16

答案(点此获取答案解析)

B,D

同类题2

工业上在合成塔中采用下列反应合成甲醇:CO(g)+2H2(g)⇌CH3OH(g)△H=QkJ/mol

(1)判断该可逆反应达到平衡状态的标志是(填字母序号)____ 

a、生成CH3OH的速率与消耗CO的速率相等

b、混合气体的密度不变

c、混合气体的平均相对分子质量不变

d、CH3OH、CO、H2的浓度都不再发生变化

(2)如表所列数据是该可逆反应在不同温度下的化学平衡常数(K)

温度

250℃

300℃

350℃

K

2.041

0.270

0.012

①由表中数据判断Q____ 0(填“>”、“<”或“=”)

②某温度下,将2mol CO和6mol H2充入2L的密闭容器中,充分反应后,达到平衡测得c(CO)=0.2mol•L﹣1,此时对应的温度为____ ;CO的转化率为____ 

(3)请在图中画出压强不同,平衡时甲醇的体积分数(φ)随温度(T)变化的两条曲线(在曲线上标出P1、P2、,且p1<P2____ 

(4)要提高CO的转化率,可以采取的措施是____ (填字母序号).

a、升温  b、加入催化剂  c、增加CO的浓度  d、通入H2加压账   e、通人惰性气体加压   f、电离出甲醇

(5)已知一定条件下,CO与H2在催化剂的作用下生成5mol CH3OH时,能量的变化为454kJ.在该条件下,向容积相同的3个密闭容器中,按照甲、乙、丙三种不同的投料方式加人反应物,测得反应达到平衡时的有关数据如下:

容器

反应物投入量

1molCO、2molH2

1mol CH3OH

2mol CH3OH

平衡时数据

CH3OH的浓度(mol•L﹣1

c1

C2

C3

反应吸收或放出的能量(KJ)

a

b

c

体系压强(Pa)

P1

P2

P3

反应物转化率

α1

α2

α3

下列说法正确的是____ (填字母序号).

A、2c1>c3    B、a+b<90.8     C、2P2<P3      D、α13<1.


同类题5

任务型阅读

    The rules about how to talk, eat and sit, which are highly limited, are observed in most Western restaurants and homes. ____ Many Westerners have no idea how to act at the Chinese dinner table. No forks or knives for them to use! The Chinese host makes great, sweeping arm movements that go over large sections of the table, passing over both food and friends alike. ____ However, it leaves many foreigners at a loss for what to do.

    In my childhood home, dinner was enjoyed with low voices, and the topics that we could discuss were very limited. ____ If I had to leave the table to use the toilet, I had to excuse myself without mentioning what it was that I was going to do. “May I be excused, please? I need to wash my hands.” I would say. My mother would say, “Sure.” My father would often play a joke on me by saying, “____

    As for eating, we did it quietly. No eating noises were allowed. Everything must be done as quietly as possible. If any sound was created by eating food or drinking, it would be considered as bad manners!

    ____He is to sit up straight with the recessive hand (usually the left) in one's lap holding a napkin while the dominant hand (usually the right) holds the fork or spoon. The only time one is allowed to have both hands on the table is when he is using a knife to cut something.

A. The scene is fantastic.

B. Your hands don't look dirty!

C. How one sits at the table is also prescribed.

D. Can't you think up a better excuse than that?

E. In general they were all strictly forbidden topics.

F. They're completely different from what we find here in China.

G. We were not allowed to talk about anything that made listeners uncomfortable.