tính khối lượng CuSO4 cần lấy để có tổng số nguyên tử đúng bằng số nguyên tử trong 9 g H2O

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\(\dfrac{1}{2}x+\dfrac{1}{3}.\left(x-2\right)=\dfrac{1}{4}\)

\(\dfrac{1}{2}x+\dfrac{1}{3}x-\dfrac{1}{3}.2=\dfrac{1}{4}\)

\(\dfrac{1}{2}x+\dfrac{1}{3}x-\dfrac{2}{3}=\dfrac{1}{4}\)

\(\left(\dfrac{1}{2}+\dfrac{1}{3}\right)x=\dfrac{1}{4}+\dfrac{2}{3}\)

\(\left(\dfrac{3}{6}+\dfrac{2}{6}\right)x=\dfrac{3}{12}+\dfrac{8}{12}\)

\(\dfrac{5}{6}x=\dfrac{11}{12}\)

\(x=\dfrac{11}{12}:\dfrac{5}{6}\)

\(x=\dfrac{11}{12}.\dfrac{6}{5}\)

\(x=\dfrac{11}{10}\)

1 + 2 - 3 - 4 + 5 + 6 - 7 - 8 + ... + 37 + 38 - 39 - 40

= ( 1+2-3-4 ) + ( 5+6-7-8 ) + ... + ( 37+38-39-40)

= (-4) + (-4) +... + (-4)

= (-4) . 10 (DO CÓ 10 NHÓM)

= -40

Cân bằng các PTHH sau :

a) \(\left(NH_4\right)_2CO_3+NaOH\rightarrow Na_2CO_3+NH_3+H_2O\)

b) \(Cu+H_2SO_4\rightarrow CuSo_4+SO_2+H_2O\)

c) \(KMnO_4+HCl\rightarrow KCl+MnCl_2+Cl_2+H_2O\)

d) \(FeSO_4+KMnO_4+H_2SO_4\rightarrow Fe_2\left(SO_4\right)_3+K_2SO_4+MnSO_4+H_2O\)

e) \(Al+HNO_3\rightarrow Al\left(NO_3\right)_3+NH_4NO_3+H_2O\)

đảo ngữ câu đk loại 1

Chuyển các câu sau sang đảo ngữ:

1. If it is warm tomorrow, we will have a picnic.

Should ...............................................................................................

2. If your cold becomes worse, you must see the doctor.

Should ...............................................................................................

3. Take part in the English club and your speaking skill will be improved.

Should ...............................................................................................

4. Keep your feet dry or you will have a cold.

Should ...............................................................................................

5. If you want to go out tonight, make up your room.

Should ...............................................................................................

6. I'll be very angry if he makes more mistakes.

Should ...............................................................................................

7. If you leave your house unlocked, It will be broken into.

Should ...............................................................................................

8. If she forget her book, she can share with me.

Should ...............................................................................................

9. Turn down the radio or you will wake the baby up.

Should ...............................................................................................

10. If you are asked to sing an english song, what will you do?

Should ...............................................................................................

11. Will you phone the police first if someone breaks into your house?

Should ...............................................................................................

12. If he asks to bring hot water, tell him to wait for five munites.

Should ...............................................................................................