Nhân biết 3 dd sau NaCl, Na2SO4, H2SO4

2 câu trả lời

Đáp án:

 

Giải thích các bước giải:

-Trích mẫu thử cho mỗi lần thí nghiệm

-Dùng quỳ tím cho vào các mẫu thử:

 +Hóa đỏ:$H_{2}$$SO_{4}$.

 +Không đổi màu:NaCl, $Na_{2}SO_{4}$

- Cho dd $BaCl_{2}$ tác dụng với NaCl, $Na_{2}SO_{4}$:

 +Xuất hiện kết tủa trắng:$BaSO_{4}$⇒$Na_{2}SO_{4}$

 PTHH:$BaCl_{2}$+$Na_{2}SO_{4}$→$BaSO_{4}$+2NaCl

 +Không có phản ứng hóa học xảy ra⇒dung dịch ban đầu là NaCl.

Trích dung dịch thành các mẫu thử nhỏ, rồi cho quỳ tím:

+) Mẫu thử làm quỳ tím hóa đỏ: `H_2SO_4`.

+) Mẫu thử không làm đổi màu quỳ tím: `NaCl, Na_2SO_4` (Nhóm I).

Cho dung dịch `AgNO_3` đi qua mẫu thử nhóm I:

+) Mẫu thử xuất hiện kết tủa trắng: `NaCl`.

`->` `AgNO_3 + NaCl -> AgCl\downarrow + NaNO_3`

+) Không hiện tượng: `Na_2SO_4`.

$#BROTHERS$

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I.  MULTIPLE CHOICE (8.0 points)

Mark the letter A, B, C, or D to indicate the word whose underlined part is pronounced differently front that of the rest in each of the following questions.

1. A. oceanic    B. remote    C. occasion    D. metro

2. A. festival    B. cultural    C. sculpture    D. virtual

Mark the letter A, B, C, or D to indicate the word that differs from the other three in the position of primary stress in each of the following questions.

3. A. external    B. determine    C. mysterious    D. customer

4. A. miraculous    B. individual    C. certificate    D. astronomy

Mark the letter A, B, C, or D to indicate the underlined part that needs correction in each of the following questions.

5. Now that the stress of examinations are over, we can go somewhere for our holiday.

                     A                     B                     C                     D

6. The English summer course will start in May 29th and finish in August.

                     A                     B                     C                     D

7. There were so a lot of people trying to leave the burning building that the police

             A                B             C

had a great deal of trouble controlling them.

                   D

Mark the letter A, B, C, or D to indicate the correct answer to each of the following questions.

8. The earthworm is a worm _______in moist, warm soil in many geographical areas.

    A. where is it found       B. is found

    C. and found it               D. which is found

9. Our flight from Amsterdam to London was delayed    the heavy fog.

    A. as a result     B. on account     C. instead of     D. due to

10. It is_______ to translate each lesson into your language. This is not a good way to study English.

    A. productive     B. unproductive     C. producing     D. unproducing

11. A good clock always keeps_______ time.

    A. certain    B. accurate    C. true    D. serious

12. It seems that the world record for this event is almost impossible to_______.

    A. meet    B. compare    C. beat    D. balance

13. The soldier was punished for_______ to obey his commanding officer's order.

    A. refusing    B. regretting    C. objecting    D. resisting

14. It is believed that she'll be a billionaire by the time she_______ forty.

    A. is    B. was    C. will be    D. would be

15. Some of the passengers spoke to reporters about their_______ in the burning bus.

    A. occasion    B. happening    C. event    D. experience

16. _______the rise in unemployment, people still seem to be spending more.

    A. Nevertheless    B. Meanwhile    C. Despite    D. Although

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