Вопрос школьника по предмету Химия
II. При змішуванні 250г води з 25г цукру утворився розчин Обчисліть масову
частку розчиненої речовин в утвореному розчині.
Ответ учителя по предмету Химия
Ответ:
Дано : Розв’язок
m(H2O)=250г W=m(розчин.реч)/m(розчину)*100%
m(цукру)=25г m(розчину)=250г+25г=275г
Знайти : m(розчин.реч)=25г
W(розчин.реч)=? W=25г/275г=0,09*100%=9%
Відповідь:9%
Объяснение:
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a) look c) was looking
b) am looking d) have been looking
2. Last summer we wanted a relaxing holiday, so we … to stay on a small island.
a) choose c) had chosen
I
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3. Mathematics … hard. I don’t understand it.
a) are c) was
b) is d) were
4. While we … for the train, it started to rain.
a) waited c) was waiting
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5. The police officer said that every house in that street … already by the police.
a) search c) had been searched
b) were searched d) searched
6. There is going to be a big art exhibition. It… a lot of visitors.
a) attracts c) has attracted
b) will attract d) attracted
7. The result of his investigation … in the newspaper soon.
a) publish c) will be published
b) be published d) is published
8. When they arrived home, their children … outside the door waiting for them.
a) sit c) was sitting
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9. We … a new computer not long ago. Now the job will be done much more quickly.
a) had bought c) bought
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10. He was sorry that he … to me for so long.
a) didn’t write c) hadn’t been writing
b) haven’t been writing d) hasn’t been writing
11. The ring you found … be returned to an old lady who had lost it.
a) can c) have to
b) must d) are to
12. Everybody in our team played … except the captain.
a) bad c) worst
b) badly d) the worst
13. You know much, but you know … than your teacher.
a) little c) least
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14. Small shops are not as … as supermarkets.
a) more convenient c) most convenient
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15. Sarah is a very good pianist. She plays … piano very well.
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Срочно!!!!!!!!!
1. Молекула ДНК состоит из 250 нуклеотидов,из них 20% приходится на тиминовый нуклеотид.Найдите количество всех типов нуклеотидов.
2. В молекуле белка 61 аминокислотный остаток.Сколько нуклеотидов находится в ДНК,кодирующей этот белок?Какова длина этой молекулы?
Прошу коротко обьяснить решение,а то совсем туго.Заранее огромное СПАСИБО!