Choose the best answer in each sentence below by circling it.
1. You are late. If you …… a few minutes earlier, you …… him.
A. came / would meet B. had come / would have met
C. come / will meet D. had come / would meet
2. “Can I borrow your car for this evening?”
“Sure, but Nora’s using it right now. If she …… it back in time, you’re welcome to borrow it.”
A. brings B. would bring C. will bring D. brought
3. We’re going to lose this game …… the team doesn’t start playing better soon.
A. if B. unless C. although D. whereas
4. If I …… somebody else, I’d like to be a film star.
A. could be B. would be C. become D. must be
5. If he had told me the truth, I …… him.
A. would have not punished B. would not have punished
C. would not punish D. will not punish
6. If they had not given me advice, I …… again.
A. would have failed B. would fail C. would have been failed D. wouldn’t fail
7. …… immediately, I will call a policeman.
A. Unless you leave B. If you leave C. If you didn’t leave D. Unless you left
8. Bill …… more photographs if he …… more film.
A. would have taken / had had B. would have taken / had
C. would take / has had D. would take / had had
9. If there …… no floods last year, the crop …… better.
A. had been / would have been B. were / would be
C. had / would have been D. was / would have been
10. Had you told me that this was going to happen, I …… it.
A. would never have believed B. don’t believe
C. hadn’t believed D. can’t believe
11. If someone …… into the store, smile and say, “May I help you?”
A. comes B. came C. come D. could come
12. If I had a chance to do creative work, I …… happy working in an office.
A. would be B. will be C. would have D. will feel
13. If they …… soon, I’m not going to wait.
A. don’t come B. won’t come C. hadn’t come D. didn’t come
14. If I …… hungry, I …… something. But I am not hungry now.
A were / would eat B. had been / would have eaten
C. had been / would eat D. were / would have eaten
15. You won’t pass the examination …… you study more.
A. unless B. as C. if D. whether
16. I’m playing tennis tomorrow …… it’s raining.
A. unless B. if C. as long as D. provided
17. Tell him to ring me if you …… him.
A. see B. saw C. have seen D. had seen
18. Unless she ……, she’ll be late.
A. hurries B. didn’t hurry C. hurried D. doesn’t hurry
19. Would George be angry if I …… his bicycle without asking?
A. took B. take C. had taken D. would take
20. I …… you a postcard while I was on holiday if I …… your address.
A. would have sent / had had B. would have sent / had
C. would send / had D. would send / had had
21. …… still my friend if I were put in prison?
A. Would you be B. Will you be C. Would you D. Would you are
22. If anybody …… any question, please ask me after class.
A. has B. have C. don’t have D. doesn’t have
23. If I weren’t working for an accounting firm, I …… in a bank.
A. would be working B. will work C. have worked D. work
24. He said, “…… watch TV all the evening if you wish.”
A. You may B. You have to C. You need to D. You should
25. If he ……, please tell me.
A. comes B. won’t come C. will come D. come
A, C3H7COOH + C2H5OH → C3H2CÔC2H5 + H2O
B, 1,88
CH3[CH2]2COOH+C2H5OHCH3[CH2]2COOC2H5+H2O𝐶𝐻3[𝐶𝐻2]2𝐶𝑂𝑂𝐻+𝐶2𝐻5𝑂𝐻𝐻2𝑆𝑂4đc,𝑡∘𝐶𝐻3[𝐶𝐻2]2𝐶𝑂𝑂𝐶2𝐻5+𝐻2𝑂(Sản phẩm thu được là ethyl butyrate) b. Tính giá trị của m𝑚 Để tính khối lượng ester, chúng ta thực hiện các bước sau: 1. Tính số mol các chất tham gia:
- Phân tử khối butyric acid ( C4H8O2𝐶4𝐻8𝑂2): 𝑀 =88 g/mol
- Phân tử khối ethanol ( C2H6O𝐶2𝐻6𝑂): 𝑀 =46 g/mol
2. Xác định chất hết - chất dư:⇒𝑛butyricacid =1,7688 =0 , 02 mol
⇒𝑛ethanol =1,2846 ≈0 , 0278 mol
Theo phương trình, tỉ lệ mol là 1:1. Ta thấy 0 , 02 <0 , 0278, do đó butyric acid hết, ethanol dư. Tính toán lượng ester theo butyric acid.
⇒𝑛ester(lýthuyt) =𝑛butyricacid =0 , 02 mol 3. Tính khối lượng ester thực tế ( m𝑚):
m=nester (lý thuyt)×Mester×H100𝑚=𝑛ester(lýthuyt)×𝑀ester×𝐻100
C3H7COOH+C2H5OHH2SO4đcC3H7COOC2H5+H2O𝐶3𝐻7𝐶𝑂𝑂𝐻+𝐶2𝐻5𝑂𝐻𝐻2𝑆𝑂4đc𝑡∘𝐶3𝐻7𝐶𝑂𝑂𝐶2𝐻5+𝐻2𝑂(Butyric acid + Ethanol ⇌⇌ Ethyl butyrate + Nước) b. Tính giá trị của m 1. Tính số mol các chất tham gia:
- Phân tử khối của butyric acid ( C3H7COOH𝐶3𝐻7𝐶𝑂𝑂𝐻): 𝑀 =88 g/mol.
- Phân tử khối của ethanol ( C2H5OH𝐶2𝐻5𝑂𝐻): 𝑀 =46 g/mol.
2. Xác định chất hết - chất dư:nbutyric acid=1,7688=0,02mol𝑛butyricacid=1,7688=0,02mol
nethanol=1,2846≈0,0278mol𝑛ethanol=1,2846≈0,0278mol
Theo phương trình, tỉ lệ mol là 1 ∶ 1. Ta thấy 0 , 02 <0 , 0278, do đó ethanol dư và tính toán lượng ester theo butyric acid (chất thiếu). 3. Tính khối lượng ester (m) theo lý thuyết:
- Theo phương trình: 𝑛esterlýthuyt =𝑛butyricacid =0 , 02 mol.
- Phân tử khối của ethyl butyrate ( C3H7COOC2H5𝐶3𝐻7𝐶𝑂𝑂𝐶2𝐻5): 𝑀 =116 g/mol.
4. Tính khối lượng ester thực tế thu được (với hiệu suất 81%):mlý thuyt=0,02×116=2,32gam𝑚lýthuyt=0,02×116=2,32gam
m=mlý thuyt×H100=2,32×81100=1,8792gam𝑚=𝑚lýthuyt×𝐻100=2,32×81100=1,8792gam Đáp số:
a) CH3CH2CH2COOH + C2H5OH ⇌ CH3CH2CH2COOC2H5 + H2O (H2SO4 đặc, t°) b) n(axit) = 1,76 / 88 = 0,02 mol n(ancol) = 1,28 / 46 ≈ 0,0278 mol → axit hết (chất giới hạn) n(este) lt = 0,02 mol m(este) lt = 0,02 × 116 = 2,32 g m(thực tế) = 2,32 × 81% = 1,8792 g ≈ 1,88 g
a,C3H7COOH+C2H5OH---------C3H7COOC2H5+H2
b,m=mlythuyet×H÷100=2,32×81÷100=1,8792gam
- 𝑀𝐶3𝐻7𝐶𝑂𝑂𝐻 =88 g/mol ⇒𝑛acid =1,7688 =0 , 02 mol
- 𝑀𝐶2𝐻5𝑂𝐻 =46 g/mol ⇒𝑛alcohol =1,2846 ≈0 , 0278 mol
2. Xác định chất giới hạn:So sánh tỉ lệ mol: 0 , 02 <0 , 0278. Do đó, hiệu suất phản ứng tính theo butyric acid. 3. Tính khối lượng ester ( m𝑚):
- Theo phương trình: 𝑛esterlýthuyt =𝑛acid =0 , 02 mol
- Khối lượng ester theo lý thuyết: 0 , 02 ×116 =2 , 32 gam (với 𝑀ethylbutyrate =116)
- Khối lượng ester thực tế với hiệu suất 81 %:
Kết luận: Giá trị của m𝑚 là 1,8792 gam.m=2,32×81100=1,8792gam𝑚=2,32×81100=1,8792gam
m=nester×Mester×H100=0,02×116×81100=1,8792gam𝑚=𝑛ester×𝑀ester×𝐻100=0,02×116×81100=1,8