\(a/n_{Fe}=\dfrac{2,52}{56}=0,045mol\\ 3Fe+2O_2\xrightarrow[]{t^0}Fe_3O_4\\ n_{O_2}=\dfrac{0,045.2}{3}=0,03mol\\ V_{O_2}=0,03.22,4=0,672l\\ b/2KClO_3\xrightarrow[]{t^0}2KCl+3O_2\\ n_{KClO_3}=\dfrac{0,03.2}{3}=0,02mol\\ m_{KClO_3}=0,02.122,5=2,45g\)

\(n_{Fe}=\dfrac{1,68}{56}=0,03\left(mol\right)\)

\(3Fe+2O_2\rightarrow\left(t^o\right)Fe_3O_4\)

 0,03   0,02               0,01  ( mol )

\(m_{Fe_3O_4}=0,01.232=2,32\left(g\right)\)

\(V_{kk}=0,02.22,4.5=2,24\left(l\right)\)

\(2KClO_3\rightarrow\left(t^o\right)2KCl+3O_2\)

   \(\dfrac{1}{75}\)                               0,02   ( mol )

\(m_{KClO_3}=\dfrac{1}{75}.122,5=1,63\left(g\right)\)

a,nFe=1,68/56=0,03 mol

Ta có PTHH : 3Fe + 2O2 --> Fe3O4 (1) ( ở trên dấu --> có to nha )

Theo PTHH ta có :

nFe3O4=1/3nFe=1/3.0,03=0,01 mol

nO2=2/3nFe=2/3.0,03=0,02 mol

=>mFe3O4= 0,01.232=2,32g

=>Vkk=5.(0,02.22,4)=2,24 l

b, Ta có PTHH: 2KClO3 --> 2KCl + 3O2 (2) ( trên dấu --> vẫn có to )

Gọi x là số mol KClO3 cần dùng ( x > 0 )

Theo PTHH (3) và theo bài ra ta có PTHH sau:

2/3x=0,02 

=> x=0,03 mol

=> mKClO3= 0,03.122,5= 3,675g

a) nFe = 16,8/56 = 0,3 (mol)

PTHH: 3Fe + 2O2 -> (t°) Fe3O4

Mol: 0,3 ---> 0,2 ---> 0,1

mFe3O4 = 0,1 . 232 = 23,2 (g)

b) VO2 = 0,2 . 22,4 = 4,48 (l)

Vkk = 4,48 . 5 = 22,4 (l)

c) H = 100% - 20% = 80%

nO2 (LT) = 0,2 : 80% = 0,25 (mol)

PTHH: 2KMnO4 -> (t°) K2MnO4 + MnO2 + O2

nKMnO4 = 0,25 . 2 = 0,5 (mol)

mKMnO4 = 0,5 . 158 = 79 (g)

\(n_{Fe_3O_4}=\dfrac{m_{Fe_3O_4}}{M_{Fe_3O_4}}=\dfrac{23,2}{232}=0,1mol\)

\(3Fe+2O_2\rightarrow\left(t^o\right)Fe_3O_4\)

0,3       0,2              0,1          ( mol )

\(m_{Fe}=n_{Fe}.M_{Fe}=0,3.56=16,8g\)

\(V_{O_2}=n_{O_2}.22,4=0,2.22,4=4,48l\)

\(V_{kk}=\dfrac{4,48.100}{20}=22,4l\)

\(2KMnO_4\rightarrow\left(t^o\right)K_2MnO_4+MnO_2+O_2\)

    0,4                                         0,2               ( mol )

\(n_{KMnO_4}=\dfrac{0,4}{85\%}=\dfrac{8}{17}mol\)

\(m_{KMnO_4}=n_{KMnO_4}.M_{KMnO_4}=\dfrac{8}{17}.158=74,3529g\)

3Fe+2O₂-to>Fe₃O₄

0,3------0,2-------0,1mol

n Fe3O4=\(\dfrac{23,2}{232}\)=0,1 mol

->m Fe=0,3.56=16,8g

b)

VO2=0,2.22,4=4,48l

=>Vkk=4,48.5=22,4l

c)2KMnO₄-to>K₂MnO₄+MnO₂+O₂

   0,4-------------------------------------0,2

=>m KMnO4=0,4.158.\(\dfrac{100}{85}\)=74,35g

CH4+2O2-to>CO2+2H2O

0,075---0,15

n O2=\(\dfrac{3,36}{22,4}\)=0,15 mol

=>VCH4=0,075.22,4=1,68l

\(n_{O_2}=\dfrac{3,36}{22,4}=0,15mol\)

\(CH_4+2O_2\rightarrow\left(t^o\right)CO_2+2H_2O\)

 0,075  0,15                                    ( mol )

\(V_{CH_4}=0,075.22,4=1,68l\)

\(n_{O_2}=\dfrac{3,36}{22,4}=0,15mol\)

   CH₄ + 2O₂ \(\underrightarrow{t^o}\) CO₂ + 2H₂O

  0,075    0,15                               ( mol )

\(V_{CH_4}=0,075.22,4=1,68l\)

PTHH: \(3Fe+2O_2\underrightarrow{t^o}Fe_3O_4\)

Ta có: \(n_{Fe}=\dfrac{4,2}{56}=0,075\left(mol\right)\) \(\Rightarrow n_{O_2}=0,05\left(mol\right)\)

\(\Rightarrow V_{O_2}=0,05\cdot22,4=1,12\left(l\right)\) \(\Rightarrow V_{kk}=\dfrac{1,12}{21\%}\approx5,33\left(l\right)\)

Đáp án D

số mol của 11,2 lít khi Oxi là:

\(n_{O_2}=\dfrac{V}{22,4}=0,5\left(mol\right)\)

Vậy S có khối lượng là:

\(m_S=n.M=0,5.32=16\left(g\right)\)

\(n_{Fe}=a\left(mol\right),n_S=b\left(mol\right)\)

\(n_{O_2}=\dfrac{6.72}{22.4}=0.3\left(mol\right)\)

\(m_{hh}=56a+32b=20\left(g\right)\left(1\right)\)

\(3Fe+2O_2\underrightarrow{t^0}Fe_3O_4\)

\(S+O_2\underrightarrow{t^0}SO_2\)

\(n_{O_2}=\dfrac{2}{3}a+b=0.3\left(mol\right)\left(2\right)\)

\(\left(1\right),\left(2\right):a=0.3,b=0.1\)

\(\%Fe=\dfrac{0.3\cdot56}{20}\cdot100\%=84\%\)

\(\%S=16\%\)