D

My sister usually meets her friends at the coffee in the evening

Take off

D

B

2Al+6HCl->2AlCl3+ 3H2

n(H2)=0,025mol

n(al)= 1/60 mol

m(Al)= 0,45g

m(Cu)= 25-0,45=24,55g

%m(Cu)=98,2%

%m(Al)=1,8%

Cu+2H2SO4(đ)-> CuSO4+SO2+H2O

2Al +6H2SO4(đ)-> Al2(SO4)3 + 3SO2+6H2O

n(so2)=n(Cu)+1,5n(al)= 24,55/64 +1,5*1/60 =523/1280 mol

V(so2)=9,1525lit

C

B

sửa f, (x-y/3)(x² +xy/3 +y² /9)

a, (6x-y)(6x+y)

b, (5x+y)²

C, (3x+4y)² 

d,(2x-3y² )(2x+3y²)

E, (x-2)(x²  +4x+4)

f, (x-y/3)(x²  + 2xy/3 + y²/9)