Một sợi dây phơi quần áo bằng đồng được mắc nối tiếp với một dây nhôm. Có hiện tượng gì xảy ra ở chỗ nối hai kim loại khi để lâu ngày?

Nguyên tắc chung được dùng để điều chế kim loại là:

Để điều chế các kim loại Na, Mg, Ca trong công nghiệp, người ta dùng cách nào sau đây?

Có 4 ion Ca²⁺, Al³⁺, Fe²⁺, Fe³⁺. Ion có số electron ở lớp ngoài cùng nhiều nhất là:

Một sợi dây phơi quần áo bằng đồng được mắc nối tiếp với một dây nhôm. Có hiện tượng gì xảy ra ở chỗ nối hai kim loại khi để lâu ngày?

Dãy gồm các kim loại đều tác dụng được với dung dịch HCl nhưng không tác dụng với dung dịch HNO₃ đặc, nguội là:

Các chất: Cl₂, O₂, dung dịch HCl, khí hiđro clorua, dung dịch CuSO₄, dung dịch HNO₃ đặc nguội, dung dịch FeCl₃. Số chất có thể tác dụng được với Fe là:

Trong các trường hợp sau, trường hợp nào kim loại bị ăn mòn điện hóa?

Cho hỗn hợp gồm 1,2 (mol) Mg và x (mol) Zn vào dung dịch chứa 2 mol Cu²⁺ và 1 (mol) Ag⁺ đến khi các phản ứng xảy ra hoàn toàn, thu được một dung dịch chứa ba ion kim loại. Trong các giá trị sau đây, giá trị nào của x thỏa mãn trường hợp trên?

Cho hỗn hợp Al, Fe tác dụng với hỗn hợp dung dịch AgNO₃, Cu(NO₃)₂ thu được chất rắn X gồm 3 kim loại. Cho X tác dụng với HCl dư, thấy có khí bay lên. Thành phần của chất rắn X là:

Trong quá trình điện phân dung dịch CuSO₄ (các điện cực trơ), ở anot xảy ra phản ứng:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 24 to 28:

Few people now realize the reality of global warming and its effects on the world’s climate. Many scientists (24) _______ the blame for recent natural disasters on the increase in the world’s temperatures and are convinced that, more than ever before, the Earth is at (25) _______ from the forces of the wind, rain and sun. According to them, global warming is making extreme weather events, such as hurricanes and droughts, even more severe and causing sea levels all around the world to rise. Environmental groups are putting pressure on governments to take action to reduce the amount of carbon dioxide which is given (26) _______ by factories and power plants, thus attacking the problem at its source. They are in (27) _______ of more money being spent on research into solar, wind, and wave energy devices, which could then replace existing power (28) _______. Some scientists, however, believe that even if we stopped releasing carbon dioxide and other gases into the atmosphere tomorrow, we would have to wait several hundred years to notice the results. Global warming, it seems, is to stay.

Question 24:       

Cho m gam Mg vào dung dịch X gồm 0,03 mol Zn(NO3)2 và 0,05 mol Cu(NO3)2, sau một thời gian thu được 5,25 gam kim loại và dung dịch YCho dung dịch NaOH vào dd Y khối lượng kết tủa thu được là 6,67 gam. Giá trị của m là         

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 24 to 28:

Few people now realize the reality of global warming and its effects on the world’s climate. Many scientists (24) _______ the blame for recent natural disasters on the increase in the world’s temperatures and are convinced that, more than ever before, the Earth is at (25) _______ from the forces of the wind, rain and sun. According to them, global warming is making extreme weather events, such as hurricanes and droughts, even more severe and causing sea levels all around the world to rise. Environmental groups are putting pressure on governments to take action to reduce the amount of carbon dioxide which is given (26) _______ by factories and power plants, thus attacking the problem at its source. They are in (27) _______ of more money being spent on research into solar, wind, and wave energy devices, which could then replace existing power (28) _______. Some scientists, however, believe that even if we stopped releasing carbon dioxide and other gases into the atmosphere tomorrow, we would have to wait several hundred years to notice the results. Global warming, it seems, is to stay.

Question 25:       

Hòa tan hoàn toàn 6,5 gam Zn bằng dung dịch H2SO4 loãng thu được V lít H2 (đktc). Giá trị của V là:         

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 31 to 35:

The Internet has truly transformed how students do their homework. (31) ____homework today still means spending time in the library, it’s for a different reason. Rather than using books for research, students today are (32) ______to the Internet to download enormous amounts of data available online. In the past, students were limited to their school’s (33) _________ of books. In many cases, they got to the school library and found out that someone had already taken the books they needed. Nowadays, such inconvenience can be avoided since the Internet never runs out of information. Students, however, do have to (34)_____sure that the information they find online is true. Teachers have also benefited from the homework which is done on the Internet. They do not need to carry student's papers around with them any more. This is because online (35)______allow students to electronically upload their homework for their teachers to read and mark. Of course, this also means that students can no longer use the excuse that the dog ate their homework!

Question 33:

Hòa tan hoàn toàn l,18g hỗn hợp X gồm Al và Cu trong dung dịch HCl thu được 0,672 l khí (đktc). Phần trăm về khối lượng Cu trong X là?         

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 31 to 35:

The Internet has truly transformed how students do their homework. (31) ____homework today still means spending time in the library, it’s for a different reason. Rather than using books for research, students today are (32) ______to the Internet to download enormous amounts of data available online. In the past, students were limited to their school’s (33) _________ of books. In many cases, they got to the school library and found out that someone had already taken the books they needed. Nowadays, such inconvenience can be avoided since the Internet never runs out of information. Students, however, do have to (34)_____sure that the information they find online is true. Teachers have also benefited from the homework which is done on the Internet. They do not need to carry student's papers around with them any more. This is because online (35)______allow students to electronically upload their homework for their teachers to read and mark. Of course, this also means that students can no longer use the excuse that the dog ate their homework!

Question 32:  

Cho luồng khí H2 có dư đi qua ống sứ có chứa 20 gam hỗn hợp X gồm MgO và CuO nung nóng. Sau khi phản ứng hoàn toàn, sấy khô đem cân lại thấy khối lượng chất rắn giảm 3,2g. Khối lương MgO và CuO trong hỗn hợp X là?    

Dung dịch X chứa 14,6 gam HCl và 22,56 gam Cu(NO3)2. Thêm m (gam) bột sắt vào dung dịch X, sau khi phản ứng xảy ra hoàn toàn thu được hỗn hợp kim loại có khối lượng là 0,5m (gam) và chỉ tạo khí NO (sản phẩm khử duy nhất). Giá trị của m là  

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 31 to 35:

The Internet has truly transformed how students do their homework. (31) ____homework today still means spending time in the library, it’s for a different reason. Rather than using books for research, students today are (32) ______to the Internet to download enormous amounts of data available online. In the past, students were limited to their school’s (33) _________ of books. In many cases, they got to the school library and found out that someone had already taken the books they needed. Nowadays, such inconvenience can be avoided since the Internet never runs out of information. Students, however, do have to (34)_____sure that the information they find online is true. Teachers have also benefited from the homework which is done on the Internet. They do not need to carry student's papers around with them any more. This is because online (35)______allow students to electronically upload their homework for their teachers to read and mark. Of course, this also means that students can no longer use the excuse that the dog ate their homework!

Question 31: