- Gồm 3 nguyên tố Na, C và O tạo nên.

- Gồm có 2 nguyên tử Na, 1 nguyên tử C và 3 nguyên tử O liên kết với nhau trong 1 phân tử

- \(PTK_{Na_2CO_3}=23.2+12+16.3=106đvC\)

1 -e

2- g

3 - f

4-a

5-h

6-d

7-b

8-c

We still use _______ to transport rice home.

(0.5 Points)

buffalo- drawn cart

paddy field

well

blackberries

2.Choose the best answer:
Max says life in the countryside is _________ than he expected.

(0.5 Points)

more interesting

interesting

interestinger

the interesting

3.Choose the word which has different sound in the part underlined.

(0.5 Points)

missed

wanted

divided

needed

4.Choose the words that have the different stress from the others.

(0.5 Points)

generous

convenient

blackberry

interesting

5.Choose the best answer:
Looking at the ______ scenery in the countryside always brings me peace.

(0.5 Points)

convenient

friendly

colorful

expensive

6.Choose the word which has different sound in the part underlined.

(0.5 Points)

sports

plays

chores

minds

7.Choose the best answer:
I find _______ tents with my brother so much fun.

(0.5 Points)

herding

picking

putting up

going

8.Choose the best answer:
He is awarded the title of the most skillful worker of the year because he works ___ than the others.

(0.5 Points)

more skillful

less skillful

more skillfully

less skillfully

9.Choose the word which has different sound in the part underlined.

(0.5 Points)

pictures

agrees

washes

phones

10.Choose the best answer:
I like the fresh ______ in the countryside.

(0.5 Points)

kites

houses

air

mik nghĩ vậy kkk

nationnal

1. What subjects do you have today?

2. What subjects do you have today?

3. What's your favourite subjects?

4. Where will you be this weekend?

5. What will you do there?

6. Who is your Vietnamese teacher?

a

a

Phân tử khối của khí hidro là : 1.2= 2 đvC

Phân tử khối của hợp chất là: 2.22 = 44 đvC

Nguyên tử khối của nguyên tố X là:

     44 - 16 . 2 = 12 đvC

 Vậy X là nguyên tố Cacbon. Kí hiệu là C

Na₂CO₃ và 106 đvC

(x + 3)² - 6x = x² + 6x + 9 - 6x = x² + 9