Cho 3 mẫu phân bón sau kcl phân đạm NH4 NO3 và phân lân kh2 po4 2 dùng chất thử nào dưới đây để nhận biết các mẫu phân trên?

A)Dung dịch ba(Oh)2

B) dung dịch AgNO3

C) quỳ tím

D)phenolphtalein

2 câu trả lời

$\text{Đáp án:}$

$\text{Chọn A vì}$

- Trích 3 phân bón để làm mẫu thử

- Cho phân `KCl`, `NH_4``NO_3` và `Ca(`$H_2$`PO_4``)_2` vào dd $\text{Ba$(OH)_2$}$  ta thấy:
+ `KCl` ko có hiện tượng

+ `NH_4``NO_3` có mùi khai bay ra

$\text{PTHH: 2$NH_4$$NO_3$ + Ba$(OH)_2$ → Ba($NO_3$$)_2$ + 2$H_2$O + 2$NH_3$ ↑}$

+ `Ca(`$H_2$`PO_4``)_2` có kết tủa trắng

$\text{PTHH: Ca($H_2$$PO_4$$)_2$ + 3Ba$(OH)_2$ → Ca$(OH)_2$ +  $Ba_3$$(PO_4$$)_2$ ↓ + 4$H_2$O}$

$\text{#blackwolf4869}$

Giải thích các bước giải:

 Chọn A: Dung dịch $Ba(OH)_2$

Cho mẫu thử 3 phân bón $KCl$, $NH_4NO_3$ và $Ca(H_2PO_4)_2$ vào dung dịch $Ba(OH)_2$:

+ Nếu mẫu nào có khí mùi khai bay ra thì đó là $NH_4NO_3$

PTHH:

$2NH_4NO_3+Ba(OH)_2→Ba(NO_3)_2+2NH_3↑+H_2O$$

+ Nếu mẫu nào tạo kết tủa trắng thì đó là $Ca(H_2PO_4)_2$

PTHH:

$Ca(H_2PO_4)_2+3Ba(OH)_2→Ca(OH)2+Ba_3(PO_4)_2↓+4H_2O$

+ Nếu không có hiện tượng gì xảy ra thì đó là $KCl$ 

Câu hỏi trong lớp Xem thêm

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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