Cho 2g hỗn hợp Fe và kim loại hóa trị II vào dd HCl dư thu đc 1,12 lít H2 đktc. Mặt khác nếu hòa tan 4,8g kim loại hóa trị II đó thì cần dùng chưa tới 500 ml dd HCl 1M. Xác định kim loại hóa trị II

2 câu trả lời

Đáp án:

$Mg$

Giải thích các bước giải:

Đặt KL là M

$PTHH:$

$Fe+2HCl\to FeCl_2+H_2\uparrow$

$M+2HCl\to MCl_2+H_2\uparrow$

Đặt KL trung bình là R

$PTHH:R+2HCl\to RCl_2+H_2\uparrow$

$\Rightarrow n_R=n_{H_2}=\dfrac{1,12}{22,4}=0,05(mol)$

$\Rightarrow M_R=\dfrac{2}{0,05}=40$

$\Rightarrow M_M<M_R<M_{Fe}=56$(do $M_{Fe}>M_R)$

$\Rightarrow M_M<40(1)$

Mặt khác: $2n_M=n_{HCl}<0,5.1=0,5$

$\Rightarrow n_M<0,25$

$\Rightarrow M_M<\dfrac{4,8}{0,25}=19,2(2)$

$(1)(2)\Rightarrow 19,2<M_M<40$

Mà $M(II)\Rightarrow M:Mg$

Vậy KL là magie

Đáp án:

 

Giải thích các bước giải:

 ảnh

bổ sung câu cuối quên ghi 

=>M là  magie

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I.  MULTIPLE CHOICE (8.0 points)

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                     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

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                   D

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

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    A. where is it found       B. is found

    C. and found it               D. which is found

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

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    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

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

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

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

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