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Câu 27: B
Câu 28: B
Câu 29: A
Câu 30: D
Câu 31: A
Câu 32: B
\(\Leftrightarrow\left(x-100\right)\left(\dfrac{1}{10}+\dfrac{1}{12}+\dfrac{1}{14}+\dfrac{1}{16}+\dfrac{1}{17}\right)=0\)
\(\Leftrightarrow x=100\) vì \(\left(\dfrac{1}{10}+\dfrac{1}{12}+\dfrac{1}{14}+\dfrac{1}{16}+\dfrac{1}{17}\right)\ne0\)
\(\Leftrightarrow S=\left\{100\right\}\)
1 B
2 C
3 C
4 A
5 C
6 B
7 D
8 C
9 B
10 B
11 D
12 C
13 D
14 D
15 A
16 emigrated
17 invited
18 patient
19 deaf
20 distance
21 assistant
22 collections
23 noon
24 are going to meet
25 on
Ta có: \(\left\{{}\begin{matrix}n_{H_2}=\dfrac{3,36}{22,4}=0,15\left(mol\right)\\n_{SO_2}=\dfrac{6,72}{22,4}=0,3\left(mol\right)\end{matrix}\right.\)
PTHH: \(2Al+6HCl\rightarrow2AlCl_3+3H_2\uparrow\)
0,1____0,3_____0,1_____0,15 (mol)
\(2Al+6H_2SO_{4\left(đ\right)}\xrightarrow[]{t^o}Al_2\left(SO_4\right)_3+3SO_2\uparrow+6H_2O\)
0,1______0,3__________0,05____0,15_____0,3 (mol)
\(Cu+2H_2SO_{4\left(đ\right)}\xrightarrow[]{t^o}CuSO_4+SO_2\uparrow+2H_2O\)
0,15_____0,3________0,15___0,15_____0,3 (mol)
Ta có: \(m_{Al}+m_{Cu}=0,1\cdot27+0,15\cdot64=12,3\left(g\right)\)
Bài 7:
PTHH: \(Mg+H_2SO_4\rightarrow MgSO_4+H_2\uparrow\)
Ta có: \(n_{H_2SO_4}=0,2\cdot1=0,2\left(mol\right)=n_{Mg}=n_{H_2}=n_{MgSO_4}\)
\(\Rightarrow\left\{{}\begin{matrix}m_{Ag}=15,6-0,2\cdot24=10,8\left(g\right)\\V_{H_2}=0,2\cdot22,4=2,24\left(l\right)\\C_{M_{MgSO_4}}=\dfrac{0,2}{0,2}=1\left(M\right)\end{matrix}\right.\)
\(\dfrac{5x-15}{5x^2}\) = \(\dfrac{5\left(x-3\right)}{5x^2}\) = \(\dfrac{x-3}{x^2}\)
=> B
Câu 2:
\(a,\Rightarrow x=-23+15=-8\\ b,\Rightarrow5\left(x+4\right)=85\\ \Rightarrow x+4=17\Rightarrow x=13\\ c,\Rightarrow5^{x+2}=24+1=25=5^2\\ \Rightarrow x+2=2\Rightarrow x=0\\ d,\Rightarrow x+4+x+5⋮9\\ \Rightarrow2x+9⋮9\\ \Rightarrow2x⋮9\Rightarrow x\in\left\{0;9\right\}\left(0< x< 10\right)\)
C
1 cooking
2 listening
3 reading
4 playing
5 cycling
1 People collect a lot of things such as stamps, milk bottle labels, comic books as well as car toys
2 She is 20 years old
3 She is a hairdresser
4 It is collecting candy shells
5 Her friends and relatives
B
1 F
2 F
3 F
4 F
5 T
7: \(=\dfrac{x+7+x+x-7}{x\left(x+7\right)}=\dfrac{3x}{x\left(x+7\right)}=\dfrac{3}{x+7}\)