Duy Ank dạ vâng, em viết nhầm thành Fe₂O₃ ạ.

Se, As, P, N, O, Br, Cl, F.

PTHH: 3Fe +2O₂ →Fe₃O₄

\(+n_{Fe}=\dfrac{11,2}{56}=0,2\left(mol\right)\)

Theo PTHH ta có: 

\(+n_{O_2}=\dfrac{2}{3}n_{Fe}=\dfrac{2}{15}\left(mol\right)\)

\(+n_{Fe3O4}=\dfrac{1}{2}n_{Fe}=0,1\left(mol\right)\)

\(+V_{O2}=\dfrac{2}{15}.22,4=2,98\left(lit\right)\)

\(+m_{Fe2O3}=0,1.160=16\left(gam\right)\)

PTHH: C₂H₄ +Br₂ →C₂H₄Br₂

+n_C2H4=\(\dfrac{1,1,2}{28}=0,04\left(mol\right)\)

+\(V_{C2H4}=0,04.22,4=0,896\left(lit\right)\)

+THEO PTHH TA CÓ: 

\(+n_{C2H4Br2}=n_{C2H4}=0,04\left(mol\right)\)

\(+m_{C2H4Br2}=0,04.188=7,52\left(gam\right)\)

Theo mình thì mùa xuân ấm hơn mùa đông, là thời gian thích hợp để thay lông.

d) 

⇔(2-3x)(2x+1)=(3x+2)(-2x-3)

⇔4x+2-6x²-3x=6x²-9x-4x-6

⇔4x-6x²-3x-6x²+9x+4x=-6-2

⇔14x=-8

⇔x=\(-\dfrac{4}{7}\)

Vậy S= {\(-\dfrac{4}{7}\)}

c)

⇔x(x+1) = (x+4)(x-1)

⇔x²+x=x²-x+4x-4

⇔x²+x-x²+x-4x=-4

⇔-2x=-4

⇔x=2

Vậy S={2}

a)

⇔\(\dfrac{2x-5}{x+5}-\dfrac{3x+15}{x+5}=0\)

⇔\(\dfrac{3x-5-3x-15}{x+5}=0\)

⇔\(-x-20=0\)

⇔\(x=-20\)