<span>1)FeCo3+Zn=ZnCo3+Fe</span>
<span>2)2NaCl=2Na+Cl2</span>
<span>2Na+S=Na2S</span>
<span>Na2S+O2=Na2SO4</span>
<span>Na2SO4+2AgNO3=NaNO3+2Ag2SO4</span>
<span>3. 2Al+3O2= 2Al2O3</span>
<span>Al+S=Al2S3</span>
<span>Al+Cl2= AlCl3</span>
<span>2Al+3H2O-Al(OH)3+H2</span>
<span>2Al+3H2SO4=Al2(SO4)3+3H2</span>
Al+HgCl= Hg+AlCl3
2Al+NaOH=2NaAlO2
Решение:
w(э) = Ar (э) · n(э)\Mr(в-ва)
Mr(Fe₂(SO₄)₃ = 56·2+32·3+16·12= 400
w(O) = 16·12\400 = 0,48 или 48,0%
Ответ: 48,0% (3)