how important is tv to you?
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1. I used to stay up late to watch football matches last year, but now I don't.
2. There used to be some trees in the fields, but now there aren't any.
3. Anna used to live with her parents.
4. He used to be a poor man, but he becomes a rich businessman.
5. They didn't use to go to the cinema every Sunday last year.
6. In the past my hair used to be much shorter than now.
7. I used to have time to collect stamps when I was in primary school.
8. Did you use to go to the beach when you lived in Nha Trang?
9. Mr Hung used to go to work by motorbike, but now he goes to work by bus.
10. There used to be traffic jams in this street during rush hours, but now the street becomes wider.
vừa đủ thì dễ rồi
PTHH : \(CaS+2HBr-->CaBr_2+H_2S\uparrow\)
\(n_{H_2S}=\frac{0,672}{22,4}=0,03\left(mol\right)\)
Theo pthh : \(n_{CaS}=n_{H_2S}=0,03\left(mol\right)\)
\(n_{HBr}=2n_{H_2S}=0,06\left(mol\right)\)
\(n_{CaBr_2}=n_{H_2S}=0,03\left(mol\right)\)
\(\Rightarrow\hept{\begin{cases}m_{CaS}=0,03\cdot72=2,16\left(g\right)=m\\m_{ddHBr}=\frac{0,06\cdot81}{9,72}\cdot100=50\left(g\right)=m_1\end{cases}}\)
Theo ĐLBTKL :
\(m_{CaS}+m_{ddHBr}=m_{ddCaBr_2}+m_{H_2S}\)
=> \(2,16+50=m_{ddCaBr_2}+0,03\cdot34\)
=> \(m_{ddCaBr_2}=51,14\left(g\right)=m_2\)
=> \(C\%_{ddCaBr_2}=\frac{0,03\cdot200}{51,14}\cdot100\%\approx11,73\%\)
=> \(x\approx11,73\)
dễ nhưng vẫn nên check lại ...
PTHH
2KMnO4 ---> K2MnO4 + MnO2 + O2
a---------------0,5a----------0,5a---0,5a
KClO3 ---> KCl + 3/2 O2
b-------------b---------1,5b
Theo pt ta có hpt
0,5a + 1,5b = 0,2
142a + 74,5b = 21,65
=> a = 0,1 => m KMnO4 = 15,8 ( g
b = 0,1 => m KClO3 = 12,25 ( g )
dịch tiếng anh ra -tv quan trọn như thế nào đối với bạn
TV is very important. They are what entertain us and be human. There are many people who love television. But TV is also bad for the body: It makes you obese, increases your risk of diabetes, makes you tired, ...