1 A

2 C

3 A

4 D

5 C

6 B

7 B

8 A

9 B

10 D

Bài 5

\(n_{Al_2O_3}=\dfrac{10,2}{102}=0,1\left(mol\right)\)

\(n_{HCl}=\dfrac{18,25}{36,5}=0,5\left(mol\right)\)

PTHH: Al₂O₃ + 6HCl --> 2AlCl₃ + 3H₂O

Xét tỉ lệ: \(\dfrac{0,1}{1}>\dfrac{0,5}{6}\) => Al dư, HCl hết

PTHH: Al₂O₃ + 6HCl --> 2AlCl₃ + 3H₂O

            \(\dfrac{1}{12}\)<----0,5------->\(\dfrac{1}{6}\)----->0,25

=> \(\left\{{}\begin{matrix}m_{Al\left(dư\right)}=10,2-\dfrac{1}{12}.102=1,7\left(g\right)\\m_{AlCl_3}=\dfrac{1}{6}.133,5=22,25\left(g\right)\\m_{H_2}=0,25.18=4,5\left(g\right)\end{matrix}\right.\)

Bài 6

a) \(n_{H_2}=\dfrac{2,24}{22,4}=0,1\left(mol\right)\)

\(n_{Mg}=\dfrac{4,8}{24}=0,2\left(mol\right)\)

PTHH: Mg + 2HCl --> MgCl₂ + H₂

           0,1<-------------0,1<----0,1

=> \(n_{Mg\left(pư\right)}=0,1\left(mol\right)< 0,2\)

=> Mg dư => HCl hết

b) \(m_{MgCl_2}=0,1.95=9,5\left(g\right)\)

\(m_{Mg\left(dư\right)}=\left(0,2-0,1\right).24=2,4\left(g\right)\)

h tới mai mà k cs ng lm thì t lm hết h đi ngủ :>

1 stilt houses

2 speciality

3 diverse

4 unique

5 folk dances

6 costume

7 heritage site 

8 ornaments 

9 terraced fields 

10 ethnic minorities

`3)(x+4)/(x-3)-(x-3)/(x+4)=(x^2+18x+7)/(x^2+x-12)`

`đk:x ne 3,x ne -4`

Nhân 2 vế với `(x-3)(x+4) ne 0` ta có:

`(x+4)^2-(x-3)^2=x^2+18x+7`

`<=>x^2+8x+16-x^2+6x-9=x^2+18x+7`

`<=>14x+7=x^2+18x+7`

`<=>x^2+4x=0`

`<=>x(x+4)=0`

Vì `x ne -4=>x+4 ne 0`

`<=>x=0`

Vậy `S={0}`

23 D

24 C

25 A

26 C

27 D

28 C

29 B

30 B

31 C

32 C

33 B

34 C

35 C

36 C

37 D

38 C

39 C hoặc A (mk nghĩ là  A)

40 D

1 C

2 A

3 B

4 B

5 D

6 D

7 B

8 B

9 D

10 C

11 C

12 A

13 A

14 B

15 A

16 B

17 D

18 C

19 D

20 B

21 B

1 There was an interesting documentary on television last night

2 Environmentally friendly vehicles are encouraged to develop

3 The festival starts with an opening parade through the streets where people walk

4 Solar energy is the cleanest and the most abudant source of energy

5  Overpopulation is one of the main reasons of air pollution

18 She hasn't seen her elder sister since 1999

19 It's years since she last wrote to me

20 It's ten years since Robert and Catherine were married

19. It's years since she last wrote to me.

20. It's ten years since Robert and Catherine were married .

9 The last time I saw him was 8 days ago

10 It is Monday when I last took a bath

11 Samuel has kept a diary since 1997

12 We have learned English for 5 years

13 I have lived in HCM City since I was 8

14 She started teaching the children in this remote village for 5 months

15 The last time he wrote to me was in April