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17 tháng 1 2022
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) \(m_{MgCl_2}=0,1.95=9,5\left(g\right)\)
\(m_{Mg\left(dư\right)}=\left(0,2-0,1\right).24=2,4\left(g\right)\)
DT
Đỗ Thanh Hải
CTVVIP
13 tháng 9 2021
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
6 tháng 6 2021
`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}`
4 ấy
DT
Đỗ Thanh Hải
CTVVIP
19 tháng 7 2021
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
DT
Đỗ Thanh Hải
CTVVIP
19 tháng 7 2021
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
DT
Đỗ Thanh Hải
CTVVIP
19 tháng 7 2021
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
DT
Đỗ Thanh Hải
CTVVIP
21 tháng 7 2021
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
DT
Đỗ Thanh Hải
CTVVIP
21 tháng 7 2021
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
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