Phần trăm khối lượng của oxi trong oxit cao nhất của R là 73%. Phần trăm khối lượng của nguyên tố R trong hợp chất khí với hiđro là 75% (trong đó R có số oxi hóa thấp nhất).

a) Xác đinh nguyên tố R.

b) Viết công thức phân tử, công thức electron, công thức cấu tạo của hai hợp chất trên.

: Cho m (g) Mg, Al vào 250 ml dd X chứa hỗn hợp HCl 1M và H₂SO₄ 0,5M thu được 5,32 lít khí H₂ ( ở đktc) và dd Y ( Coi thể tích dd không thay đổi).

a. Trong dd Y axit dư hay hết?

b. Tính giá trị m?

c. Cô cạn dd Y thu được a(g) muối. Tính a?

Hòa tan 2,74 (g) Kim loại R thuộc nhóm A vào 200ml ddHCl 0,1M thu được 0,448 lít khí H2 ( ở đktc). Xác định R?

b. Article

1. She's __ __ good musician. She plays ___ __ piano beautifully.

2. I don't see him often, only once or twice ___ ___ month.

3. I’m studying ___  ____ French and___  ____  Italian.

4. Shall we sit outside? ___ ____ sun is really warm.

5. I don’t use____   ___ sugar when I’m cooking.

6. I think___ ___ piano is one of ____ ___ easiest instruments to play.

7. It's___ ____ fast car. Its top speed is 150 miles___ ____ hour.

8. Nam's father bought him    __ __ bike that he wanted for his birthday.

9. __ __ Statue of Liberty was __  gift of friendship from __  __ France to__ ___ United States.

10.You should help __________poor.

11._________Football is a popular sport in Vietnam.

12. ___________ man that we met has just come.

b. Article

1. She's __ __ good musician. She plays ___ __ piano beautifully.

2. I don't see him often, only once or twice ___ ___ month.

3. I’m studying ___  ____ French and___  ____  Italian.

4. Shall we sit outside? ___ ____ sun is really warm.

5. I don’t use____   ___ sugar when I’m cooking.

6. I think___ ___ piano is one of ____ ___ easiest instruments to play.

7. It's___ ____ fast car. Its top speed is 150 miles___ ____ hour.

8. Nam's father bought him    __ __ bike that he wanted for his birthday.

9. __ __ Statue of Liberty was __  gift of friendship from __  __ France to__ ___ United States.

10.You should help __________poor.

11._________Football is a popular sport in Vietnam.

12. ___________ man that we met has just come.

1. Mr. Nam doesn’t speak English as fluently as I do.  

-> I ………………………………………………………………………

2. Joe is not as hard-working as his brother.

→ Joe’s brother .............................................................................................

3. He drives more carefully than his friend.

-> His friend…………………………………………..

4. This exercise is less difficult than that one.

-> That exercise ………………………………

5. Playing tennis is not as interesting as playing football.

-> Playing football ………………………..

c. superlative

1. No students studies better than Tom.  

-> Tom ……………………………………………………………………..

2. Russia is bigger than any other country in the world.

→ Russia.............................................................................................

3. Nothing is more precious than happiness and health.

-> Happiness…………………………………………………..

4. The Nile is longer than any other river in the world.  

    The Nile is ……………………………………

5. No exercise is more difficult than this exercise.

-> This exercise ……………………………….

6.I’ve never seen such a nice bouquet of wedding flowers.

-> This is the……………………………..