Trung hòa 250 ml dung dịch H2SO4 1M bằng V ml dung dịch Ca(OH)2 2M. Giá trị của V là

A. 175

B. 150

C. 125

D. 200

1. It's a pity I can't play the guitar well.

I wish I could play the guitar well

2. My mother spent three hours making a dress.

It took my mother three hours to make a dress

3. We haven't been to the concert for over a year.

The last time we went to the concert was over a year ago

4. We last saw our grandfather two years ago.

We haven't seen our grandfather for two years

5. I have never read such a romantic story

6.It’s nearly twenty years since my father saw my uncle.

My father  hasn't seen my uncle for nearly twenty years.

7. It’s pity I don’t have a computer .

I wish  I had a computer.

8. They are going to build a supermarket in my neighborhood.

A supermarket is going to be built in my neighborhood.

9. The last time we went to a cinema was two years ago .

We haven’t gone to a cinema for 2 years

10. he hasn’t been back to his village for over 20 years .

It’s over 20 years since he last went back to his village.

11. I’m sorry I’m not able to go with you .

I wish I were able to go with you

12. Spending the weekend in the countryside is very exciting.

It’s very exciting to spend the weekend in the countryside.

13. Why don’t we go to the countryside?

I suggested going to the countryside. 

14. Practice speaking English every day or you can’t improve your English .

If you practice speaking English everyday, you will improve your English

15. The boy is sorry he doesn’t have his teacher’s address .

The boy wishes he had his teacher's address

16. “ where do you live?” The interviewer said to me .

The interviewer asked me where I lived.

17. “ I’m very busy . I’ll ring you tomorrow ,” Susan said to me .

Susan told me that she was very busy and she would ring me the next day.

18. “ Can you speak any foreign languages ?” Henry said to me .

Henry asked me if i could speak any foreign languages.

19. “ Don’t shout ,” I said to Jim.

I ordered Jim not to shout.
20. The last time we saw him was on Monday .
Wehaven't seen him since Monday.

https://tuhoc365.vn/qa/tron-100-ml-dung-dich-a-gom-khco3-1m-va-k2co3-1m-vao-100-ml-dung-dich-b-gom-nahco3-1m-va-na2co3-1m-t/

Gọi số lần nguyên phân là k ta có:

(2^k - 1) x 10 x 2n = 2480 (1)

Số NST môi trường cung cấp cho giảm phân là: 2^k x 10 x 2n = 2560 (2) 

Lấy (2) - (1) ta có:

2^k x 10 x 2n - (2^k - 1) x 10 x 2n = 2560 - 2480 = 80

→ 10 x 2n = 80 → 2n = 8

Thay 2n = 8 vào (1) ta có: (2^k - 1) x 10 x 8 = 2480 suy ra k = 5. Số lần nguyên phân của mỗi tế bào là 5 lần.

Vậy số tế bào sinh giao tử tạo thành là: 10 x 2^5 = 320

b, Số giao tử đực tạo thành là: 320 x 4 = 1280

Số hợp tử tạo thành là: 1280 x 10% = 128

Số tế bào sinh trứng cần cho thụ tinh là: 128 : 25% = 512

 a) m rắn=4,08 gam

b) CM Cu(NO3)2 dư=0,35M; CM Fe(NO3)2=0,2M

c) V NO2=1,792 lít

Giải thích các bước giải:

Ta có: nAgNO3=0,2.0,1=0,02 mol; nCu(NO3)2=0,5.0,2=0,1 mol; nFe=2,24/56=0,04 mol

Fe + 2AgNO3 -> Fe(NO3)2 + 2Ag

Vì nAgNO3=0,02 mol; nFe =0,04 -> Fe dư -> tạo ra 0,02 mol Ag và Fe phản ứng 0,01 mol -> dư 0,03 mol

Fe + Cu(NO3)2 -> Fe(NO3)2 + Cu

Vì Cu(NO3)2=0,1 mol; nFe =0,03 mol -> Cu(NO3)2 dư =0,07 mol ; nCu=0,03 mol

Rắn thu được gồm Ag 0,02 mol và Cu 0,03 mol -> m rắn=4,08 gam

Dung dịch sau phản ứng chứa Cu(NO3)2 dư 0,07 mol và Fe(NO3)2 0,04 mol (Bảo toàn Fe)

-> CM Cu(NO3)2=0,07/0,2=0,35M; CM Fe(NO3)2=0,04/0,2=0,2M

Hòa tan rắn bằng HNO3 đặc

Ag + 2HNO3 -> AgNO3 + NO2 + H2O

Cu + 4HNO3 -> Cu(NO3)2 +2NO2 + 2H2O

-> nNO2=nAg + 2nCu=0,02+0,03.2=0,08 mol -> V NO2=0,08.22,4=1,792 lít

II. Choose the correct answer

1.  ……….. he was sick, he still turned up for his guitar lesson.

A. Although           B. Because             C. Despite             D. Since

2. The old man was very fond ………….. telling stories.

A. to                     B. about                C. of                        D. for

3. They ………. haven't replied to the letter we sent two months ago

A. still                            B. yet                       C. already                  D. ever

4. His face looks …………., but I can’t remember his name.

A. similar                   B. alike                    C. memorial               D. familiar

5. The fire officer is coming to …………the building tomorrow.

A. look                  B. inspect                   C. witness                  D. watch

6. The boys hurt ……….. when they injured down  from the tree.

A. one another        B. each other           C. himself           D.themselves

7. I’m sure they were …………lies

A. making                  B. telling                  C. doing                   D. saying

8. She’d rather die than ………..Peter.

A. she married          B. to marry                C. marrying               D. marry.

9. My sisiter will have a ........... Course of English next month.

A.  two month        B. two– onths     C.  two–month       D. second-month

10. To  prepare his .............. works , he spent his while days in his library.

A. science             B. scientific            C. scientist                 D. sciences

11. The less we study , the ................. we are

A. worse                   B. bad                       C. well                      D. good

12. After the summer holiday, the children all looked................

A. health               B. healthy               C. healthful               D. healthily.

13. The person................ he works with like him very much.

A. who                  B. whom                  C. whose                  D.  which.

14. Football........................... all over the world.

A. plays                   B. is playing              C. is played               D. played

15. I know .................... she has gone for holiday.

A. when                  B. where                   C. why                      D. which.