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6 tháng 10 2021

Gọi kim loại là R, hóa trị n, do R là kim loại nên n có thể bằng 1, 2 hoặc 3

\(2R + 2nHCl \rightarrow 2RCl_n + nH_2\)

\(n_{H_2}=\dfrac{3,36}{22,4}= 0,15 mol\)

Theo PTHH:

\(n_{R}= \dfrac{2}{n} . n_{H_2}= \dfrac{2}{n} . 0,15 = \dfrac{0,3}{n} mol\)

\(\Rightarrow M_R= \dfrac{3,6}{\dfrac{0,3}{n}}=\dfrac{3,6n}{0,3}=12n\)

Do n bằng 1, 2 hoặc 3

Ta thấy n= 2 và MR= 24 g/mol thỏa mãn

R là Mg

6 tháng 10 2021

Gọi CTHH của kim loại là M, x là hóa trị của M

PTHH: M + xHCl ---> MClx + \(\dfrac{x}{2}\)H2.

Ta có: \(n_{H_2}=\dfrac{3,36}{22,4}=0,15\left(mol\right)\)

Theo PT: \(n_M=\dfrac{1}{\dfrac{x}{2}}.n_{H_2}=\dfrac{1}{\dfrac{x}{2}}.0,15=\dfrac{2}{x}.0,15=\dfrac{0,3}{x}\left(mol\right)\)

=> \(M_M=\dfrac{3,6}{\dfrac{0,3}{x}}=\dfrac{3,6x}{0,3}=12x\left(g\right)\)

Biện luận:

x1234
M1224

36

48
 Loại(TM)loạiLoại

 

Vậy MM = 24(g)

Dự vào bảng hóa trị, suy ra:

M là magie (Mg)

 

15 tháng 11 2021

\(d,=\dfrac{3y}{5x\left(x-y\right)}\\ e,=\dfrac{5x\left(x+2\right)\left(2-x\right)}{4\left(x-2\right)\left(x+2\right)}=\dfrac{-5x}{4}\\ f,=\dfrac{3\left(x-6\right)\left(x+6\right)}{2\left(x+5\right)\left(6-x\right)}=\dfrac{-3\left(x+6\right)}{2\left(x+5\right)}\\ g,=\dfrac{3xy\left(x-3y\right)\left(x+3y\right)}{2x^2y^2\left(x-3y\right)}=\dfrac{3\left(x+3y\right)}{2xy}\\ h,=\dfrac{45x^2y\left(x-y\right)\left(x+y\right)}{10xy\left(y-x\right)}=\dfrac{-9x\left(x+y\right)}{2}\\ i,=\dfrac{12\left(a-b\right)\left(a+b\right)\left(a^2+ab+b^2\right)}{3\left(a+b\right)\left(a-b\right)^2}=\dfrac{4\left(a^2+ab+b^2\right)}{a-b}\)

15 tháng 11 2021

e: \(=\dfrac{5\left(x+2\right)}{4\left(x-2\right)}\cdot\dfrac{-2\left(x-2\right)}{x+2}=\dfrac{-10}{4}=-\dfrac{5}{2}\)

6 tháng 10 2021

\(n_{H_2}=\dfrac{3,36}{22,4}=0,15\left(mol\right)\)

PTHH: 2R + 2nHCl → 2RCln + nH2

Mol:     \(\dfrac{0,3}{n}\)                                      0,15

\(M_R=\dfrac{3,6}{\dfrac{0,3}{n}}=12n\left(g/mol\right)\)

Vì R là kim loại nên có hóa trị l,ll,lll

        n         l          ll         lll
   MR      12        24         36
 Kêt luận  loại   thỏa mãn      loại

  ⇒ R là magie (Mg)

 

15 tháng 11 2021

3. I think collecting stamps is interesting

15 tháng 11 2021

Giúp e 2 câu còn lại với ạ

15 tháng 11 2021

\(a,=x^2+x+4x+4=\left(x+1\right)\left(x+4\right)\\ b,=x^2+2x-3x-6=\left(x-3\right)\left(x+2\right)\\ c,=x^2-2x-3x+6=\left(x-2\right)\left(x-3\right)\\ d,=3\left(x^2-2x+5x-10\right)=3\left(x-2\right)\left(x+5\right)\\ e,=-3x^2+6x-x+2=\left(x-2\right)\left(1-3x\right)\\ f,=x^2-x-6x+6=\left(x-1\right)\left(x-6\right)\\ h,=4\left(x^2-3x-6x+18\right)=4\left(x-3\right)\left(x-6\right)\\ i,=3\left(3x^2-3x-8x+5\right)=3\left(x-1\right)\left(3x-8\right)\\ k,=-\left(2x^2+x+4x+2\right)=-\left(2x+1\right)\left(x+2\right)\\ l,=x^2-2xy-5xy+10y^2=\left(x-2y\right)\left(x-5y\right)\\ m,=x^2-xy-2xy+2y^2=\left(x-y\right)\left(x-2y\right)\\ n,=x^2+xy-3xy-3y^2=\left(x+y\right)\left(x-3y\right)\)

15 tháng 11 2021

Bào quan riboxom trong chất tế bào có chức năng gì? 

Dạ Anh/Chị trong group giải giúp em câu này với ạ. Em cám ơn nhiều.      I.          Use the correct form of the word given in each sentence:1.     Like beverage cans and bottles, this _______________ can be recycled. (produce)2.     The next stage in the _______________ of television is interactive TV. (develop)3.     You’d better put an _______________ in the local paper to sell your house. (advertise)4.     I enjoy the constant _______________ with students from other classes....
Đọc tiếp

Dạ Anh/Chị trong group giải giúp em câu này với ạ. Em cám ơn nhiều.

      I.          Use the correct form of the word given in each sentence:

1.     Like beverage cans and bottles, this _______________ can be recycled. (produce)

2.     The next stage in the _______________ of television is interactive TV. (develop)

3.     You’d better put an _______________ in the local paper to sell your house. (advertise)

4.     I enjoy the constant _______________ with students from other classes. (interact)

5.     The Internet is a very useful means of _______________. (communicate)

6.     There’s a lot of crime and _______________ on TV today. (violent)

7.     Her novel is known to everyone. It is _______________ read. (wide)

8.     Because Hoa lives in a remote area, the Internet isn’t _______________ for her. (availability)

9.     My brother would like to be a _______________. (journal)

10.  He was a town_______________ who had to stand in markets and public spaces, shouting the news to the residents of the town. (cry)

11.  I find this newspaper _______________. I can get much useful knowledge from it. (inform)

12.  Computers are becoming _______________ popular. They make everything faster and more reliable. (increase)

13.  Watching TV has become one of the most popular forms of _______________. (entertain)

14.  Nowadays, the Internet is _______________ used. We can see many products. (commerce)

15.  _______________ is a film or radio or television program giving facts about something.(document)

16.  The show brought _______________ to millions of viewers. (enjoy)

17.  Although this laptop was a bit _______________, I still bought it yesterday. (cost)

18.  There is a _______________ of local and international programs on TV. (vary)

19.  I’m looking forward to seeing your _______________. (respond)

20.  By learning English, we can understand more about the _______________ countries in the world. (develop)

21.  It’s _______________to try to talk to her because she never listens. (use)

22.  They walked _______________ to the room. (purpose)

23.  Alexander G. Bell was one of the greatest _______________. (invent)

24.  These mountain villages are completely _______________ in winter. (access)

25.  I found the talk both informative and _______________. (entertain)

26.  The Internet is becoming a _______________ tool for teachers. (use)

27.  For most people a good _______________ helps them get a better job. (educate)

28.  He was good at making up funny stories. He has an­­­­­­­­­­­­­_______________ mind. (invent)

    II.          Rearrange the groups of words in a correct order to make complete sentences:

1.     part of our everyday life / has increasingly / The internet / developed and become /. /

_______________________________________________________________

2.     of using the computer, / can they? / can deny the advantages / No one/

_______________________________________________________________

3.     uses the Internet / every day, / Your father / doesn’t he?

_______________________________________________________________

4.     are used / with TV / Remote controls / to interact/./

_______________________________________________________________

5.     news as / Town criers / they were walking / shouted the latest/./

__________________________________________________________________

6.     is a very fast / The Internet / for me to get information/ and convenient way/./

__________________________________________________________________

7.     most of the time / which website is useful / wandering because / I don’t know / I spend/. /

_______________________________________________________________

8.     TV viewers / can watch a variety / on different channels / of local and international programs /./

_______________________________________________________________

9.     My father / sports but / likes watching / my mother doesn’t/./

_______________________________________________________________

10.  Most people / and magazines / love reading / newspapers/./

_______________________________________________________________

0
NV
28 tháng 12 2021

23.

\(\dfrac{a-\sqrt{a}}{1-\sqrt{a}}=\dfrac{-\sqrt{a}\left(1-\sqrt{a}\right)}{1-\sqrt{a}}=-\sqrt{a}\)

Đáp án C

28 tháng 12 2021

14.\(\dfrac{\sqrt{a^3}}{\sqrt{a}}=\dfrac{a\sqrt{a}}{\sqrt{a}}=a\)

4.\(-\dfrac{1}{3}ab^3\sqrt{\dfrac{9a^2}{b^2}}=-\dfrac{1}{3}ab^3.\dfrac{-3a}{b}=a^2b^2\)

29 tháng 12 2021

Chọn D

29 tháng 12 2021

ngu toán lắm bạn

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

b