Đáp án:
\[m_{Mg}=19,2\times 12,5\%=2,4(g)\]
\[\to m_{Fe}=19,2-2,4=16,8(g)\]
\[n_{Mg}=\dfrac{2,4}{24}=0,1(mol)\]
\[n_{Fe}=\dfrac{16,8}{56}=0,3(mol)\]
Phản ứng xảy ra:
\[2Mg+O_2\to 2MgO\]
\[3Fe+2O_2\to Fe_3O_4\]
Theo PTHH:
$∑n_{O_2}=\dfrac{1}{2}.n_{Mg}+\dfrac{2}{3}.n_{Fe}=\dfrac{1}{2}.0,1+\dfrac{2}{3}.0,3=0,25(mol)$
$\to m_{O_2}=0,25.32=8(g)$
CHÚC BẠN HỌC TỐT!
Giải thích các bước giải:
$mMg=12,5%.19,2:100%=2,4g$
$=>mFe=19,2-2,4=17,5g$
Ta có: $2Mg+O2->2MgO$
$3Fe+2O2->Fe3O4$
Theo pt, ta có: $nO2(1)=1/2nMg=1/2.2,4/24=0,05mol=>mO2(1)=0,05.32=1,6g$
$nO2(1)=2/3nFe=2/3.17,5/56=0,2g=>mO2=0,2.32=6,4g$
$=>mO2=6,4+1,6=8(g)$
3.3-Dimetylhexan xác định công thức cấu tạo hợp chất này
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