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7 tháng 2 2021

Ta có : \(n_{Fe2O3}=\frac{m}{M}=\frac{16}{160}=0,1\)

PTHH phản ứng : Fe2O3 + H2 -----> Fe + H2O

=> Cân bằng PTHH : Fe2O3 + 3H2 -----> 2Fe + 3H2O

Tỉ lệ hệ số chất tham    1      :   3        :    2     :   3

gia và sản phẩm        0,1         0,3          0,2    :  0,3 

                                   mol        mol      mol         mol

=>  VH2 \(=n.22,4=0,3.22,4=6,72\left(l\right)\)                                                                   

=> mFe = n.M = 0,2 . 56 = 11,2 (g)

DD
7 tháng 2 2021

1) Định luật bảo toàn khối lượng: trong phản ứng hóa học, tổng khối lượng các chất đã tham gia phản ứng bằng tổng khối lượng các sản phẩm tạo thành. 

2) a) Ta có: \(SO_4\)có hóa trị là \(2\).

Gọi \(a\)là hóa trị của \(A\)trong \(ASO_4\).

Khi đó, theo quy tắc hóa trị: \(1a=1.2\Leftrightarrow a=2\).

Vậy trong công thức \(ASO_4\)\(A\)thể hiện hóa trị \(2\).

b) \(n_{Cu}=\frac{12,8}{64}=0,2\left(mol\right)\)

\(n_A=n_{Cu}=0,2\left(mol\right)\)

\(M_A=4,8\div0,2=24\left(đvC\right)\)

Suy ra \(A\)là \(Mg\).

7 tháng 2 2021

em nơi chị thương chị giao bài khó vcn

7 tháng 2 2021

\(1,d_{\frac{N_2}{CO_2}}=\frac{28}{44}\approx0,634\)

\(d_{\frac{N_2}{K^2}}=\frac{28}{29}\approx0,966\)

\(2,M_{Na_2SO_4}=142\left(g/mol\right)\)

\(\%Na=\frac{2.23}{142}.100\%\approx32,39\%\)

\(\%S=\frac{32}{142}.100\%\approx22,54\%\)

\(\%O=100\%-\%Na-\%S=45,07\%\)

\(3,n_{Na}=\frac{3.10^{24}}{6.10^{23}}=5\left(mol\right)\)

\(m_{Na}=5.23=115\left(g\right)\)

7 tháng 2 2021

chịu mới học lớp 5 sao biết

6 tháng 2 2021

\(nFe=\frac{m}{M}\)   

\(=\frac{42}{56}\)   

\(=0,75\left(mol\right)\)    

Vậy chọn đáp án D 

lam ho mik vsI. Chia động từ trong ngoặc cho đúng thì (Give correct tenses of the verbs)1. Mary (be) ____________________ seriously ill since last night.2. They sometimes (go) ____________________ school by bus.3. How long __________ you (study) __________ English?- I (study) ____________________ it for 7 years.4. We last (see) _____________ them last Sunday.5. I (not meet) ____________________ him since he moved to Hanoi.6. Now they (play) ____________________ happily in the school...
Đọc tiếp

lam ho mik vs

I. Chia động từ trong ngoặc cho đúng thì (Give correct tenses of the verbs)

1. Mary (be) ____________________ seriously ill since last night.

2. They sometimes (go) ____________________ school by bus.

3. How long __________ you (study) __________ English?

- I (study) ____________________ it for 7 years.

4. We last (see) _____________ them last Sunday.

5. I (not meet) ____________________ him since he moved to Hanoi.

6. Now they (play) ____________________ happily in the school yard.

7. We (not finish) ____________________ our exercises yet.

8. My friend said he (be) __________ working in Hanoi then.

9. Mr. David (just buy) ____________________ a new house.

10. They (build) ____________________ a new hospital in my neighborhood next month.

11. It (not rain) ____________________ since the beginning of this month.

12. Lan asked me if I (like) __________ pop music.

13. We (begin) ____________ to learn English three years ago. Now we (learn) __________________ for 3 years.

14. __________ you ever (be) __________ to Ho Chi Minh City?

15. The telephone (ring) __________ when we (watch) ___________ television last night.

16. Mrs Hoa (teach) _________ English in this school since she (leave) ______ the university.

17. Look! That car (run) _________________ very fast.

18. The Browns (have) ____________________ dinner at the moment.

19. He (live) ____________________ in Hanoi for 20 years.

20. Alexander Graham Bell (invent) _____________ the telephone many years ago.

21. She (be) __________ very ill now. She (not go) ____________ to school since Monday.

22. + __________ you (be) __________ to Phong Nha before?

+ Yes. I (spend) _____________ my holiday there last summer.

23. I must go now. I (phone) ________ you when I (arrive) ______________ there.

24. When I last (see) __________ them, they ( work) ___________ in a factory in Hanoi.

25. Ba's teacher (give) __________ him a lot of homework last week.

26. Tom hopes he (meet) __________ many interesting people when he goes to Hanoi next month.

27. Mai and her friends (walk) ____________________ to school now.

28. They (go) __________ to Sao Mai Movie Theater last night.

29. She (not see) ____________________ that film before.

30. My mother was waiting for me when I (come) ______________ home.

31. Ann and Susan (cook) _____________________ dinner when Martin arrived home.

32. The light (go) ______________ out while we were having dinner.

33. + What __________ you (do) ______________ at this time yesterday?

+ I (play) _____________________ games on the computer.

34. Tom! Turn off the TV. You (always watch) ____________________ TV.

35. Lan often (do) __________ her homework carefully.

36. This is the first time Hoa (meet) ____________________ Tim's family.

37. They said they (go) ____________________ to Hanoi the following day.

38. Yesterday (be) __________ a beautiful day. The Sun (shine) ____________________ brightly when we (leave) ______________ home.

39. The teacher asked me if I (know) __________ where the Statue of Liberty was.

40. Listen! Mai (play) ____________________ the piano in her room.

41. + What kind of music ____________ you (like) __________ ?

+ I like pop music.

42. In summer, the Sun usually (shine) __________________ brightly.

43. I (not finish) _______________________ reading the novel you lent me yet.

44. Julia (write) ________________________ an email to her boy friend now.

45. Jack (not meet) _______________________ Tom the last time he came to America.

2

* một số câu trực tiếp gián tiếp mình chưa học nên không làm được nhé 

18. The Browns (have) ________is having____________ dinner at the moment.

19. He (live) _________has lived___________ in Hanoi for 20 years.

20. Alexander Graham Bell (invent) ______invented_______ the telephone many years ago.

21. She (be) _____is_____ very ill now. She (not go) ______hasn't gone______ to school since Monday.

22. + _____Have_____ you (be) ____been______ to Phong Nha before?

+ Yes. I (spend) ____spent______ my holiday there last summer.

23. I must go now. I (phone) _____phoned___ you when I (arrive) ____was arriving__________ there.

24. When I last (see) ____saw______ them, they ( work) _____were working______ in a factory in Hanoi.

25. Ba's teacher (give) ____gave______ him a lot of homework last week.

26. Tom hopes he (meet) ________will meet__ many interesting people when he goes to Hanoi next month.

27. Mai and her friends (walk) __________are walking__________ to school now.

28. They (go) ______went____ to Sao Mai Movie Theater last night.

29. She (not see) _________hasn't seen___________ that film before.

30. My mother was waiting for me when I (come) ________came______ home.

31. Ann and Susan (cook) ___________were cooking__________ dinner when Martin arrived home.

32. The light (go) ______was going________ out while we were having dinner.

33. + What _____were_____ you (do) ______doing________ at this time yesterday?

+ I (play) ____________was playing_________ games on the computer.

34. Tom! Turn off the TV. You (always watch) _________always watch___________ TV.

35. Lan often (do) ____does______ her homework carefully.

36. This is the first time Hoa (meet) __________has met__________ Tim's family.

38. Yesterday (be) ______was____ a beautiful day. The Sun (shine) _______was shining_____________ brightly when we (leave) _______left_______ home.

40. Listen! Mai (play) ________is playing____________ the piano in her room.

41. + What kind of music __do__________ you (lik e) ___lik e_______ ?

+ I pop music.

42. In summer, the Sun usually (shine) _________shines_________ brightly.

43. I (not finish) ___________haven't finished____________ reading the novel you lent me yet.

44. Julia (write) _____________is writing___________ an email to her boy friend now.

45. Jack (not meet) ______________didn't meet_________ Tom the last time he came to America.

I. Chia động từ trong ngoặc cho đúng thì (Give correct tenses of the verbs)

1. Mary (be) ___________has been_________ seriously ill since last night.

2. They sometimes (go) _________go___________ school by bus.

3. How long _____have_____ you (study) ____studied______ English?

- I (study) _______have studied_____________ it for 7 years.

4. We last (see) ________saw_____ them last Sunday.

5. I (not meet) _______haven't met_____________ him since he moved to Hanoi.

6. Now they (play) _________are playing___________ happily in the school yard.

7. We (not finish) ___________haven't finished_________ our exercises yet.

8. My friend said he (be) _____will be_____ working in Hanoi then.

9. Mr. David (just buy) ________just has bought____________ a new house.

10. They (build) _________will build___________ a new hospital in my neighborhood next month.

11. It (not rain) __________hasn't rained__________ since the beginning of this month.

13. We (begin) _____began_______ to learn English three years ago. Now we (learn) __________________ for 3 years. ( xem lại đề)

14. _____Have_____ you ever (be) ____been______ to Ho Chi Minh City?

15. The telephone (ring) ___rang_______ when we (watch) _____were watching______ television last night.

16. Mrs Hoa (teach) _____taught____ English in this school since she (leave) ___has left___ the university.

17. Look! That car (run) ______is running___________ very fast.

cac ban oi lam ho mik ban nay vs I. Chia động từ trong ngoặc cho đúng thì (Give correct tenses of the verbs)1. Mary (be) ____________________ seriously ill since last night.2. They sometimes (go) ____________________ school by bus.3. How long __________ you (study) __________ English?- I (study) ____________________ it for 7 years.4. We last (see) _____________ them last Sunday.5. I (not meet) ____________________ him since he moved to Hanoi.6. Now they (play) ____________________...
Đọc tiếp

cac ban oi lam ho mik ban nay vs 

I. Chia động từ trong ngoặc cho đúng thì (Give correct tenses of the verbs)

1. Mary (be) ____________________ seriously ill since last night.

2. They sometimes (go) ____________________ school by bus.

3. How long __________ you (study) __________ English?

- I (study) ____________________ it for 7 years.

4. We last (see) _____________ them last Sunday.

5. I (not meet) ____________________ him since he moved to Hanoi.

6. Now they (play) ____________________ happily in the school yard.

7. We (not finish) ____________________ our exercises yet.

8. My friend said he (be) __________ working in Hanoi then.

9. Mr. David (just buy) ____________________ a new house.

10. They (build) ____________________ a new hospital in my neighborhood next month.

11. It (not rain) ____________________ since the beginning of this month.

12. Lan asked me if I (like) __________ pop music.

13. We (begin) ____________ to learn English three years ago. Now we (learn) __________________ for 3 years.

14. __________ you ever (be) __________ to Ho Chi Minh City?

15. The telephone (ring) __________ when we (watch) ___________ television last night.

16. Mrs Hoa (teach) _________ English in this school since she (leave) ______ the university.

17. Look! That car (run) _________________ very fast.

18. The Browns (have) ____________________ dinner at the moment.

19. He (live) ____________________ in Hanoi for 20 years.

20. Alexander Graham Bell (invent) _____________ the telephone many years ago.

21. She (be) __________ very ill now. She (not go) ____________ to school since Monday.

22. + __________ you (be) __________ to Phong Nha before?

+ Yes. I (spend) _____________ my holiday there last summer.

23. I must go now. I (phone) ________ you when I (arrive) ______________ there.

24. When I last (see) __________ them, they ( work) ___________ in a factory in Hanoi.

25. Ba's teacher (give) __________ him a lot of homework last week.

26. Tom hopes he (meet) __________ many interesting people when he goes to Hanoi next month.

27. Mai and her friends (walk) ____________________ to school now.

28. They (go) __________ to Sao Mai Movie Theater last night.

29. She (not see) ____________________ that film before.

30. My mother was waiting for me when I (come) ______________ home.

31. Ann and Susan (cook) _____________________ dinner when Martin arrived home.

32. The light (go) ______________ out while we were having dinner.

33. + What __________ you (do) ______________ at this time yesterday?

+ I (play) _____________________ games on the computer.

34. Tom! Turn off the TV. You (always watch) ____________________ TV.

35. Lan often (do) __________ her homework carefully.

36. This is the first time Hoa (meet) ____________________ Tim's family.

37. They said they (go) ____________________ to Hanoi the following day.

38. Yesterday (be) __________ a beautiful day. The Sun (shine) ____________________ brightly when we (leave) ______________ home.

39. The teacher asked me if I (know) __________ where the Statue of Liberty was.

40. Listen! Mai (play) ____________________ the piano in her room.

41. + What kind of music ____________ you (like) __________ ?

+ I like pop music.

42. In summer, the Sun usually (shine) __________________ brightly.

43. I (not finish) _______________________ reading the novel you lent me yet.

44. Julia (write) ________________________ an email to her boy friend now.

45. Jack (not meet) _______________________ Tom the last time he came to America.

1

* Một số câu trực tiếp gián tiếp mình chưa học nên không làm được, cậu tự làm nhé :

1. Mary (be) _________has been__________ seriously ill since last night.

2. They sometimes (go) _________go___________ school by bus.

3. How long ____have______ you (study) _____studied_____ English?

- I (study) ___________have studied_________ it for 7 years.

4. We last (see) _______saw______ them last Sunday.

5. I (not meet) _________haven't met___________ him since he moved to Hanoi.

6. Now they (play) __________are playing__________ happily in the school yard.

7. We (not finish) _________haven't finished___________ our exercises yet.

9. Mr. David (just buy) __________just has bought__________ a new house.

10. They (build) __________will buid__________ a new hospital in my neighborhood next month.

11. It (not rain) ________hasn't rained____________ since the beginning of this month.

14. ________Have__ you ever (be) _____been_____ to Ho Chi Minh City?

15. The telephone (ring) ____rang______ when we (watch) ______were watching_____ television last night.

16. Mrs Hoa (teach) ____taught_____ English in this school since she (leave) ___has left___ the university.

17. Look! That car (run) ______is running___________ very fast.

18. The Browns (have) ________is having____________ dinner at the moment.

19. He (live) _________has lived___________ in Hanoi for 20 years.

20. Alexander Graham Bell (invent) ______invented_______ the telephone many years ago.

21. She (be) _____is_____ very ill now. She (not go) ______hasn't gone______ to school since Monday.

22. + _____Have_____ you (be) ____been______ to Phong Nha before?

+ Yes. I (spend) ____spent______ my holiday there last summer.

23. I must go now. I (phone) _____phoned___ you when I (arrive) ____was arriving__________ there.

24. When I last (see) ____saw______ them, they ( work) _____were working______ in a factory in Hanoi.

25. Ba's teacher (give) ____gave______ him a lot of homework last week.

26. Tom hopes he (meet) ________will meet__ many interesting people when he goes to Hanoi next month.

27. Mai and her friends (walk) __________are walking__________ to school now.

28. They (go) ______went____ to Sao Mai Movie Theater last night.

29. She (not see) _________hasn't seen___________ that film before.

30. My mother was waiting for me when I (come) ________came______ home.

31. Ann and Susan (cook) ___________were cooking__________ dinner when Martin arrived home.

32. The light (go) ______was going________ out while we were having dinner.

33. + What _____were_____ you (do) ______doing________ at this time yesterday?

+ I (play) ____________was playing_________ games on the computer.

34. Tom! Turn off the TV. You (always watch) _________always watch___________ TV.

35. Lan often (do) ____does______ her homework carefully.

36. This is the first time Hoa (meet) __________has met__________ Tim's family.

38. Yesterday (be) ______was____ a beautiful day. The Sun (shine) _______was shining_____________ brightly when we (leave) _______left_______ home.

40. Listen! Mai (play) ________is playing____________ the piano in her room.

41. + What kind of music __do__________ you (lik e) ___lik e_______ ?

+ I pop music.

42. In summer, the Sun usually (shine) _________shines_________ brightly.

43. I (not finish) ___________haven't finished____________ reading the novel you lent me yet.

44. Julia (write) _____________is writing___________ an email to her boy friend now.

45. Jack (not meet) ______________didn't meet_________ Tom the last time he came to America.

6 tháng 2 2021

+) Oxit chứa 50% khối lượng oxi :

Gọi công thức hóa học của oxit là \(M_xO_y\) (x,y nguyên dương tối giản)

Ta có : \(\frac{16y}{M_M\cdot x+16y}\cdot100\%=50\%\)

=> \(32y=M_M\cdot x+16y\)

=> \(M_M=8\cdot\frac{2y}{x}\)

Ta có bảng sau : 

\(\frac{2y}{x}\)IIIIIIIVVVIVII
\(M_M\)8162432404856
KLLoạiLoạiLoạiLưu huỳnh (S)LoạiLoạiLoại

=> oxit cần tìm là SO2

=> \(M_{SO_2}=32+16\cdot2=64\) (g/mol)

+) Oxit chứa 60% khối lượng oxi :

Gọi công thức của oxit chứa 60% khối lượng oxi là \(M_aO_b\) (a,b nguyên dương tối giản)

Ta có : \(\frac{16b}{M_M\cdot a+16b}\cdot100\%=60\%\)

=> \(16b=0,6M_M\cdot a+9,6b\)

=> \(M_M=\frac{16}{3}\cdot\frac{2y}{x}\) 

Ta có bảng sau : 

\(\frac{2y}{x}\)IIIIIIIVVVIVII
\(M_M\)\(\frac{16}{3}\)\(\frac{32}{3}\)\(16\)\(\frac{64}{3}\)\(\frac{80}{3}\)32\(\frac{112}{3}\)
KLLoạiLoạiLoạiLoạiLoạiLưu huỳnh (S)Loại

=> oxit cần tìm là SO3

=> \(M_{SO_3}=32+16\cdot3=80\)(g/mol)

 Postscript : khi tìm đc ngto là lưu huỳnh, có thể lắp xuống dưới để tìm cthh của oxit còn lại, có vẻ như thế sẽ dễ hơn 

6 tháng 2 2021

bán kính hình tròn đó là

7,536 : 2 : 3,14 = 1,2 [m]

diện tích hình tròn đó là

1,2 nhân 1,2 nhân 3,14 =4,5216 [m 2]

đáp số : 4,5216m2

chúc bạn học tốt

5 tháng 2 2021

ồ vậy hả .

6 tháng 2 2021

id  miniworld của mình này:133652328/KindFabian

5 tháng 2 2021

Các đồng phân

+ C2H4O2: CH3COOH , HCOOCH3 , CH2(OH) CHO. 

+ C3H8O: CH3CH2CH2OH , CH3CH(OH) CH3 , CH3-O-CH2CH3. 

+ C5H10: CH2= CHCH2CH2CH3 , CH2= CH-CH(CH3)CH3 ,CH2= C(CH3) -CH2CH3 ,CH3-CH=CH-CH2CH3 , CH3CH=C(CH3)2.

. Các đồng phân

+ C2H4O2: CH3COOH , HCOOCH3 , CH2(OH) CHO. 

+ C3H8O: CH3CH2CH2OH , CH3CH(OH) CH3 , CH3-O-CH2CH3

+ C5H10: CH2= CHCH2CH2CH3 , CH2= CH-CH(CH3)CH3 ,CH2= C(CH3) -CH2CH,CH3-CH=CH-CH2CH3 , CH3CH=C(CH3)2.