Ban đầu, $m_{NaOH}=100.5\%=5g$
$n_{Na}=\dfrac{4,6}{23}=0,2 mol$
$\Rightarrow n_{NaOH}=0,2 mol; n_{H_2}=0,1 mol$
$m_{NaOH(dd)}=5+0,2.40=13g$
$m_{dd\text{spứ}}=m_{Na}+100-m_{H_2}=4,6+100-0,1.2=104,4g$
$\Rightarrow C\%_{NaOH}=\dfrac{13.100}{104,4}=12,45\%$
PTHH
`2Na + 2H_2O -> 2NaOH + H_2`
`n_(Na)=\frac{4,6}{23} =0,2(mol)`
Theo pthh `n_(NaOH)=n_(Na)=0,2(mol)`
`=> m_(NaOH)=0,2.40=8(g)`
`n_(H_2)=1/2.n_(Na)=0,1(mol)`
`=> m_(H_2)=0,1.2=0,2(g)`
`m_(NaOH)(trong dd )= 100.5/100=5(g)`
`=> m_(NaOH) sau = 5+8=13(g)`
`m_(dd)=4,6+100-0,2=104,4(g)`
`=>C%=\frac{13}{104,4} .100=12,45%`
giúp mình bài 10 ạ !! thankk kiu
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Exercise 3: Rewrite the following sentences that keep the same meaning. 1. I don’t play tennis as well as you do. => You …………………………………………………….…………………………… 2. I haven’t been to the dentist’s for two years. => It’s …………………………………………………….…………………………….. 3. Whenever she went to Paris she bought a new dress. => She never …………………………………………………….……………………... 4. I spent seven years at secondary school and then I went to university. => After …………………………………………………….…………………………... 5. It’s not worth living to make her change her mind. => There’s …………………………………………………….………………………... 6. He said he was not guilty of stealing the car. => He denied …………………………………………………….……………………... 7. Is this the only way to reach the city centre? => Isn’t there …………………………………………………….…………………….? 8. He never suspected that the money had been stolen. => At no time …………………………………………………….…………………….. 9. It’s my opinion that you should take more exersise. => If I…………………………………………………….……………………………... 10. I was going to leave, but because of what he said, I didn’t. => She persuaded …………………………………………………….………………… Exercise 4: Rewrite the following sentences that keep the same meaning. 1. He was very sorry that he didn’t see Andrey on her trip to London. => He greatly regretted…………………………………………………………............. 2. It’s thought that the accident was caused by human error. => The accident is…………………………………………..…………………............... 3. “Will you be visiting the Taj Mahal when you go to India?” he asked Elizabeth. => He asked ……………………………………………………………………............. 4. “I think you should try the chicken Marengo,” said the waiter. => The waiter recommended ………………………………………………….. ............ 5. This is the most delicious cake I have ever tasted. => I have …………………………………………………………………………...…... Exercise 5: Rewrite the following sentences that keep the same meaning. 1. The questions are so easy that everyone can answer them. => They’re such ………………………………………………………………………... 2. The boy will receive some money to continue his study. His parents died in a traffic accident => The boy whose ………………………………....................................................…… 3. They are producing motorbikes in Vietnam. => Motorbikes are ……………………………………………………………………… 4. I wasn’t there yesterday, so I didn’t know who he was. => If I …………………………………………………………………………………... 5. If you do not try hard, you can’t pass the examination. => Unless ………………………………………………………………………………. 6. They spent more money, they had to work harder. => The more …………………………………………………………………………… 7. People thought that the cover was made of iron. => The cover …………………………………………………………………………… 8. He went to London. He had lived there when he was a boy. => He went to London where ………………………………………………………….. 9. Jane was absent from class because of her sickness. => Because Jane was …………………………………………………………………… 10. The package was too heavy for Peter to carry. => He package was so …………………………………………………………………..
Điền từ thích hợp vào chỗ trống Albert Eistein was a German-born American (1)____ He finished his secondary (2)_____ in Switzerland, (3) ____ entered the Swiss National Polytechnic in Zurich. After his (4) _____ in 1900, he got a (5) _____ in the Swiss patent office in Bern in 1902. In 1903 he (6)____ Milaca Marci, a classmate of him at the polytechnic. In 1905 Eistein received his (7)______ from the University of Zurich for a (8)____ on the dimensions of the molecules. That same year, he published three (9)_____ of central importance to the (10)______of 20th century physics. In his papers, Eistein made significant (11)______ about the motion of particles randomly distributed in a fluid, and a revolutionary hypothesis that light can be (12) _____ as consisting (13)____ particles with individual energies. In 1905 he (14)_____ a remarkable paper known as the special theory of relativity.
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