a, Số mol nhôm ocit là 

n_Al2O3=\(\dfrac{m}{M}\)=20,4:(27 x 2 + 16 x 3)= 0,2 mol

PTHH:

                        4 Al    +   3 O₂      -^t0>  2Al₂O₃

theo pt:             4               3                   2           (mol)

theo baif ra:      x               y                   0,2           (mol)

-> n_Al  =   x = 0,2 x4 : 2 =0,4 mol

-> m_Al = 0,4 x 27 = 10,8 gam

b, theo caau a ->n_O2=y = 0,2 x 3 : 2 = 0,3 mol

-> V_O2(ddktc) = 0,3 x 22,4 =6,72 lits

-> V_KK(ddktc) = 6,72  x 5 = 33,6 lits

trên đường đi học về nếu em thấy bà cụ đánh rơi hai trăm triệu em sẽ cố gọi cụ lại và  trả lại cụ. Nếu mà cụ đã đi xa và không biết ai đánh rơi thì em sẽ ko chiếm làm của riêng mà đêm đến đồncảnh sát để liên hệ với người đã đánh mất

# Chúc bạn học tốt #

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A. casual                     B. traditional               C. international           D. social

17. Miss Nga designs clothes for ladies. She is a _______ .

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A. novels                     B. poems                     C. text reading            D. essays

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A. casual                     B. national                   C. special                     D. additional

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A. poets                       B. poems                     C. poetry                     D. poetic

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A. wear                       B. wearing                   C. wore                       D. to wear

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A. said                         B. told                         C. talked                     D. mentioned

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A. prefer                      B. like more                 C. enjoy                       D. avoid

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A. didn’t hear             B. don’t hear               C. haven’t heard         D. couldn’t hear

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A. are used                  B. has used                  C. isn’t used                D. hadn’t been used

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A. is liked                    B. likes                        C. has been liked         D. was liked

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A. were you                B. are you                    C. have you been        D. did you

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A. never                      B. any                          C. not                          D. ever

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A. gives                       B. gave                        C. is giving                  D. has given

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A. works                     B. worked                   C. has worked D. had worked

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A. was included          B. including                C. included                 D. is included

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A. of                            B. by                           C. from                        D. in

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B. just painted             D. has just been painted

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A. in                            B. to                            C. for                           D. at

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A. of                            B. in                            C. by                           D. from

50. He has written four novels ________.

A. recently                  B. one year ago           C. last year                  D .yesterday

c

B