Phân tử khối của hợp chất Al₂(SO₄)₃ là:

27.2+( 32+16.4).3= 54+96.3=54+288=342

1. The classrooms are cleaned by the students every day.

2. The letters are delivered at 7 o'clock every morning

3. English is spoken in many countries around the world

4. Volleyball is played every afternoon

5. A lot of flowers are planted in our garden

a) HC có dạng XO₃

PTK của h/c là: X+3.O=2.40=80

b) X+3.O=2.40=80

=> X+48=80

=> X=32

Tên: lưu huỳnh, kí hiệu: S

PTK của hợp chất A là

2X+S+4O=142

=> 2X+32+64=142

=> 2X=142-64-32=46

=> 2X=46

=> X=23

Vậy X là nguyên tố Natri

Xét tam giác EBC có

BEC+ECI+ACF=180

=> 90+55+ACF=180

=> ACF=35

Xét tam giác FCA có

A + AFC +ACF =180

A=180-90-35=55

xa+ya-5(x+y)=a(x+y)-5(x+y)=(x+y)(a-5)

1. cooks

2. unsafe

3. destruction

4. danger

5. locked

6. electricity

7. injured

8. safety

9. suitable

10. fortunately

11. safety

12. dangerous

13. destruction

14. cooker

15. unfortunately

16. unsuccessful

17, interesting

18. dangerous

19. suitable

20. safe

1. participate

2. easily

3. proud

4. pronounciation

5. nervousness

6. excellently

7. improvement

8. excellent

9. important

10. revision

18.b

19c

20a

21b

22a

23c

24a