Giúp câu 32
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32 D
I
1 looked for a job for some months
2 was checked by Mr Brown yesterday
3 the weather was bad, we couldn't go out
4 If it weren't raining heavily, we wouldn't cancel
III
1 It was such a boring film that we left before the end
2 I haven't seen her since 2 years ago
3 They will be punished by the teacher for being so lazy
4 They got up early so that they wouldn't be late for the meeting
\(=\lim\limits_{x\rightarrow0}\dfrac{\sqrt{4x+1}-\left(2x+1\right)+2x+1-\sqrt[3]{6x+1}}{x^2}\)
\(=\lim\limits_{x\rightarrow0}\dfrac{-\dfrac{4x^2}{\sqrt{4x+1}+2x+1}+\dfrac{x^2\left(8x+12\right)}{\left(2x+1\right)^2+\left(2x+1\right)\sqrt[3]{6x+1}+\sqrt[3]{\left(6x+1\right)^2}}}{x^2}\)
\(=\lim\limits_{x\rightarrow0}\left(-\dfrac{4}{\sqrt{4x+1}+2x+1}+\dfrac{8x+12}{\left(2x+1\right)^2+\left(2x+1\right)\sqrt[3]{6x+1}+\sqrt[3]{\left(6x+1\right)^2}}\right)\)
\(=\dfrac{-4}{1+1}+\dfrac{12}{1+1+1}=2\)
\(M_X=17.2=34\left(g/mol\right)\)
Quy đổi hh \(X\left\{{}\begin{matrix}CH_4\\C_2H_4\\C_3H_4\\C_4H_4\end{matrix}\right.\rightarrow C_xH_4\left(1< x< 4\right)\)
\(m_X=34.0,075=2,55\left(g\right)\)
Mà \(n_H=4n_X=0,3\left(mol\right)\Rightarrow n_C=\dfrac{2,55-0,3}{12}=0,1875\left(mol\right)\)
BTNT: \(\left\{{}\begin{matrix}n_{CO_2}=n_C=0,1875\left(mol\right)\\n_{H_2O}=\dfrac{1}{2}n_H=0,15\left(mol\right)\end{matrix}\right.\)
\(\Rightarrow m=m_{CO_2}+m_{H_2O}=0,1875.44+0,15.18=10,95\left(g\right)\)
Chọn D
Câu 32:
F1: 599 cao tròn: 213 cao dài: 210 thấp tròn: 65 thấp dài
<=> Tỉ lệ 9A-B- : 3A-bb : 3aaB- : 1aabb
Cây cao dài ở F1: 1/3AAbb : 2/3Aabb, tự thụ phấn:
=> (1/3AAbb : 2/3Aabb) x (1/3AAbb : 2/3Aabb)
Aabb x Aabb => (3/4A-bb:1/4aabb)
AAbb x AAbb => 1AAbb
=> Xác suất cần tìm là: 2/3*3/4 + 1/3 = 5/6
Câu 31:
PT: \(CH_2=CH_2+H_2O\underrightarrow{t^o,xt}CH_3CH_2OH\)
→ Đáp án: A
Câu 32:
Ta có: \(n_{CO_2}=\dfrac{5,6}{22,4}=0,25\left(mol\right)\)
\(n_X=\dfrac{1,12}{22,4}=0,05\left(mol\right)\)
Gọi CTPT của X là CnH2n.
\(\Rightarrow n=\dfrac{n_{CO_2}}{n_X}=5\)
Vậy: X là C5H10.
→ Đáp án: D