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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) \(m_{MgCl_2}=0,1.95=9,5\left(g\right)\)
\(m_{Mg\left(dư\right)}=\left(0,2-0,1\right).24=2,4\left(g\right)\)
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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
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`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}`
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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
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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
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1 What does Micheal usually cycle in the central park for?
2 When did Hydro power became an electricity source?
3 How many free education prohrams have they organized?
4 Who won the Best Actor at the 88th Academy Awards?
5 Where are many people from the countryside moving to find work
Ex3
1 being young, she knows how to use water efficiently
2 Mary's sickness, she couldn't go to school
3 the bad weather, she went to school on time
4 studying hard, I passed the exam
5 the heavy rain, I couldn't go to school
Ex4
1 will be built for poor children next month
2 will be sold anywhere in my hometown
3 will be invented
4 to our village will be widened next year
5 will be used to go to school by students
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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
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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
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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
46 A
47 A
48 B
49 B
50B
II
1 A
2 C
3 C
4 C
5 D
46 A
47 A
48 B
49 B
50B
II
1 A
2 C
3 C
4 C
5 D