Part 1: Rewrite each sentence beginning as shown, so that the meaning remains the same.
Example: He wrote the letter in two hours.
It took him two hours to write the letter.
1. The keepers feed the lions at 3 pm every day.
The lions ................................................................................................................................
2. We got lost because we didn't have a map.
If we ........................................................................................................................................
3. I would prefer you to deliver the sofa on Friday.
I would rather.........................................................................................................................
4. The bridge was so low that the bus couldn't go under it.
It was .......................................................................................................................................
5. That was a silly thing to say.
What ........................................................................................................................................
6. We've run out of tea.
There........................................................................................................................................
7. I last saw him when I was a student.
I haven't ..................................................................................................................................
8. Susan was too excited to sleep.
Susan was ...............................................................................................................................
9. Robert has not had a job for two years.
Robert has been .....................................................................................................................
10. She will complete the work only she is paid extra.
She will not ........................................................................................................................
Part 2 Use the words in the brackets to combine the following sentences.
1. All the students love the principal. He is very kind. (because of)
.................................................................................................................................
2. I have forgotten the tickets. I’m sorry for it. (having)
................................................................................................................................
3. I saw it with my own eyes. I believed it. (if)
................................................................................................................................
4. The house at the end of the street has been sold. It has been empty for years. (which)
.............................................................................................................................
5. It's a pity he doesn't take the doctor's advice. (wish)
............................................................................................................................
Part 3 : A friend of yours has written to you, asking for some advice. He wants to visit
your country for three weeks this summer and would like to know which places to visit,
where to stay, what sights to see, and what clothes to bring. Write to him, giving as many
suggestions as you can and mentioning any national customs that may seem strange to
him. (about 200 words)
Quặng malachit có thành phần chính là hai hợp chất của đồng được ghi bằng công thức chung là Cu2(OH)2CO3. Khi nung nóng thì hai hợp chất này bị phân huỷ, sản phẩm của phản ứng phân huỷ gồm có CuO, H2O và CO2.
a)Viết phương trình hoá học của phản ứng phân huỷ mỗi hợp chất của đồng.
b)Biết rằng khi nung nóng 4,8 kg quặng thì thu được 3,2 kg CuO cùng với 0,36 kg nước và 0,88 kg CO2. Tính tỉ lệ phần trăm về khối lượng hai hợp chất của đồng có chứa trong quặng.
Giải
a) Công thức hóa học hai hợp chất của đồng:
(C{u_2}{(OH)_2}C{O_3} o Cu{(OH)_2}vàCuC{O_3})
Các phương trình hóa học của phản ứng phân hủy:
(Cu{(OH)_2} o CuO + {H_2}O)
(CuC{O_3} o CuO + C{O_2})
b) Theo định luật bảo toàn khối lượng, khới lượng hai hợp chất của đồng đã phân hủy bằng:
({m_{Cu}}_{_2{{(OH)}_2}C{O_3}} = {m_{CuO}} + {m_{{H_2}O}} + {m_{C{O_2}}} = 3,2 + 0,36 + 0,88 = 4,44(kg))
Tỷ lệ phần trăm về khối lượng hai hợp chất của đồng có chứa trong quặng bằng:
({m_{Cu}}_{_2{{(OH)}_2}C{O_3}} = {{4,44} over {4,8}} imes 100\% = 92,5\% ) .