One of the most urgent environmental problems in the world today is the shortage of clean water. Having clean drinking water is a basic human right. However, acid rain, industrial pollution and garbage have made many sources of water undrinkable. Lakes, reservoirs and even entire seas have become vast pools of poison. Lake Baikal in Russia is one of the largest lakes in the world. It contains a rich variety of animals and plants, including 1,300 rare species that do not exist anywhere else in the world. Yet, they are being destroyed by the massive volumes of industrial effluent which pour into the lake every day. Even though laws have been made, the government does not have the power to enforce them. Most industries simply ignore the regulations. The Mediterranean Sea occupies 1% of the world’s water surface, but it is the dumping ground for 50% of all marine pollution. Almost 16 countries regularly throw industrial wastes a few miles off shore.
Water is free to everyone. A few years ago, people thought that the supply of clean water in the world was limitless. Today, many water supplies have been ruined by pollution and sewage. Clean water is now scarce, and we are at last beginning to respect this precious source. We should do something now.
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\(n_A=\dfrac{8,96}{22,4}=0,4\left(mol\right)\Rightarrow\left\{{}\begin{matrix}n_{H_2}=0,3\left(mol\right)\\n_{Cl_2}=0,1\left(mol\right)\end{matrix}\right.\)
PT: \(H_2+Cl_2\underrightarrow{^{t^o}}2HCl\)
Xét tỉ lệ: \(\dfrac{0,3}{1}>\dfrac{0,1}{1}\), ta được H2 luôn dư nếu pư hoàn toàn.
Gọi: nCl2 (pư) = a (mol) ⇒ nCl2 (dư) = 0,1 - a (mol)
Theo PT: nHCl = 2nCl2 (pư) = 2a (mol)
PT: \(Cl_2+2NaOH\rightarrow NaCl+NaClO+H_2O\)
__0,1-a____________0,1-a_____0,1-a (mol)
\(HCl+NaOH\rightarrow NaCl+H_2O\)
2a________________2a (mol)
⇒ 12,34 = mNaCl + mNaClO = 58,5.(0,1 - a + 2a) + 74,5.(0,1 - a)
⇒ a = 0,06 (mol)
\(\Rightarrow H\%=\dfrac{0,06}{0,1}.100\%=60\%\)
Bài 1:
a: \(y=x^2-4x+3\)
Vì a=1>0 nên hàm số đồng biến khi \(x>-\dfrac{b}{2a}=\dfrac{4}{2}=2\) và nghịch biến khi x<2
Khi x=2 thì \(y=2^2-4\cdot2+3=4-8+3=-1\)
Bảng biến thiên:
Vẽ đồ thị:
b: \(y=-x^2+2x-3\)
Vì a=-1<0 nên hàm số đồng biến khi \(x< -\dfrac{b}{2a}=\dfrac{-2}{2\cdot\left(-1\right)}=1\) và nghịch biến khi x>1
Khi x=1 thì \(y=-1^2+2\cdot1-3=-1+2-3=-2\)
Bảng biến thiên:
Vẽ đồ thị:
c: \(y=x^2+2x\)
Vì a=1>0 nên hàm số đồng biến khi \(x>-\dfrac{b}{2a}=\dfrac{-2}{2}=-1\); hàm số nghịch biến khi x<-1
Khi x=-1 thì \(y=\left(-1\right)^2+2\cdot\left(-1\right)=1-2=-1\)
Bảng biến thiên:
vẽ đồ thị:
d: \(y=-2x^2-2\)
Vì a=-2<0
nên hàm số đồng biến khi \(x< -\dfrac{b}{2a}=0\) và nghịch biến khi x>0
Khi x=0 thì \(y=-2\cdot0^2-2=-2\)
Bảng biến thiên:
Vẽ đồ thị:
Mọi người cho mình hỏi câu nào đúng được không ạ
Chọn D. have left → left
+, It's + time + since + S + V2/ed (sau since dùng thì qkđ)
Câu 1:
\(B=\frac{2x-3}{x-3\sqrt x}-\frac{1}{\sqrt x}=\frac{2x-3}{\sqrt x(\sqrt x-3)}-\frac{\sqrt x-3}{\sqrt x(\sqrt x-3)}\\=\frac{2x-3-\sqrt x+3}{\sqrt x(\sqrt x-3)} =\frac{2x-\sqrt x}{\sqrt x(\sqrt x-3)}=\frac{\sqrt x(2\sqrt x-1)}{\sqrt x(\sqrt x-3)}\\=\frac{2\sqrt x-1}{\sqrt x-3}(đpcm)\)
Câu 2:
Ta có:
\(A-B<0\Leftrightarrow \frac{x}{\sqrt x-3}-\frac{2\sqrt x-1}{\sqrt x-3}<0\\\Leftrightarrow \frac{x-2\sqrt x+1}{\sqrt x-3}<0\\\Leftrightarrow \frac{ (\sqrt x-1)^2}{\sqrt x-3}<0\\ \Leftrightarrow \begin{cases} \sqrt x-1\ne0\\ \sqrt x-3<0 \end{cases} (\text{vì }(\sqrt x-1)^2\ge 0)\\ \Leftrightarrow \begin{cases} \sqrt x\ne 1\\ \sqrt x<3 \end{cases}\Leftrightarrow \begin{cases} x\ne 1\\ 0\le x<9 \end{cases} \)
Kết hợp với ĐKXĐ của x, ta được: \(0< x<9;x\ne 1\)
$Toru$
Read the following passage and mark the letter A, B, C or D to indicate the correct answer to each of the questions.
One of the most urgent environmental problems in the world today is the shortage of clean water. Having clean drinking water is a basic human right. However, acid rain, industrial pollution and garbage have made many sources of water undrinkable. Lakes, reservoirs and even entire seas have become vast pools of poison. Lake Baikal in Russia is one of the largest lakes in the world. It contains a rich variety of animals and plants, including 1,300 rare species that do not exist anywhere else in the world. Yet, they are being destroyed by the massive volumes of industrial effluent which pour into the lake every day. Even though laws have been made, the government does not have the power to enforce them. Most industries simply ignore the regulations. The Mediterranean Sea occupies 1% of the world’s water surface, but it is the dumping ground for 50% of all marine pollution. Almost 16 countries regularly throw industrial wastes a few miles off shore.
Water is free to everyone. A few years ago, people thought that the supply of clean water in the world was limitless. Today, many water supplies have been ruined by pollution and sewage. Clean water is now scarce, and we are at last beginning to respect this precious source. We should do something now.
Question 36. According to the writer, one environmental problem in the world today is __________.
A. pools of poison B. safe water shortage C. population explosion D. industrial pollution
Question 37. What is the serious problem of Lake Baikal in Russia?
A. It is the only lake in Russia whose source of water is not drinkable.
B. It is polluted by massive volumes of industrial wastes discharged into it.
C. It is one of the largest lakes that contain a variety of animals and plants.
D. It has 1,300 rare species that do not exist anywhere else in the world.
Question 38. What does the word "them” in the passage refer to?
A. plants B. animals C. laws D. the government
Question 39. What is the message to the readers?
A. We should take action to protect our water sources.
B. We should limit the use of water sources.
C. We should encourage people to use safe water.
D. We should take all water sources into account.
Question 40. The word "sewage” is CLOSEST in meaning to __________.
A. plastic B. poison C. treatment D. waste
36 B
37 B
39 A
40 D