2 mol KMnO4 --> 1 Mol Oxi 
0,6 --> 0,3 
2xR + yO2 --> 2RxOy 
Rx(g) 32y (g) 
10,8 g 0,3. 32(g) 
R = 9 . 2y/x 
2y/x = 3 => R = 27 (Al)

$2KMnO_4 \xrightarrow{t^o} K_2MnO_4 + MnO_2 + O_2$

n KMnO4 = 94,8/158 = 0,6(mol)

n O2 = 1/2 n KMnO4 = 0,3(mol)

Gọi n là hóa trị kim loại R

$4R + nO_2 \xrightarrow{t^o} 2R_2O_n$

Theo PTHH :

n R = 4/n  .n O2 = 1,2/n (mol)

=> M R = 10,8 : 1,2/n = 9n

Với n = 3 thì R = 27(Al)

Vậy R là kim loại Al

4Al+3O₂-to>2Al₂O₃

0,04---0,03------0,02 mol

n _Al=\(\dfrac{1,08}{27}\)=0,04 mol

=>V_O2=0,03.22,4=0,672l

b)

2A+O₂-to>2AO

0,06--0,03 mol

=>\(\dfrac{3,84}{A}=0,06\)

=>A=64 :=>Al là Đồng

2.

PTHH:

\(2X+O_2--to->2XO\)

Theo pt:

=>\(n_X=n_{XO}=>\dfrac{3,6}{X}=\dfrac{6}{X+16}=>X=24\left(Mg\right)\)

=>oxit MgO

=> \(n_X=\dfrac{3,6}{24}=0,15\left(mol\right)\)

=> \(n_{O_2}=\dfrac{1}{2}n_X=\dfrac{1}{2}.0,15=0,075\left(mol\right)\)

=> \(2KClO_3--to->2KCl+3O_2\)

Theo pt:

\(n_{KClO_3}=\dfrac{2}{3}n_{O_2}=\dfrac{2}{3}.0,075=0,05\left(mol\right)\)

=>\(m_{KClO_3}=0,075.122,5=9,1875\left(g\right)\)

3.

lam tg tự bài 2

a)\(n_{Fe}=\dfrac{22,4}{56}=0,4mol\)

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

0,4     \(\dfrac{4}{15}\)      \(\dfrac{2}{15}\)

\(V_{O_2}=\dfrac{4}{15}\cdot22,4=5,973l\)

b)\(2KClO_3\underrightarrow{t^o}2KCl+3O_2\)

   \(\dfrac{8}{45}\)                          \(\dfrac{4}{15}\)

  \(m_{KClO_3}=\dfrac{8}{45}\cdot122,5=21,78g\)

nKClO3 = 24,5/122,5 = 0,2 (mol)

PTHH: 2KClO3 -> (t°, MnO2) 2KCl + 3O2

nO2 = 0,2/2 . 3 = 0,3 (mol)

VO2 = 0,3 . 22,4 = 6,72 (l)

\(2KMnO_4-^{t^0}->K_2MnO_4+MnO_2+O_2\\2 R+\dfrac{n}{2}O_2-^{t^0}->R_2O_n\\ n_{O_2}=\dfrac{1}{2}n_{KMnO_4}=\dfrac{94,8}{158.2}0,3mol\\ n_{O_2}=\dfrac{10,8}{R}\cdot\dfrac{n}{4}=0,3\\ n:R=\dfrac{1}{9}\\ n=3;R=27\\ R:Al\left(aluminium:nhôm\right)\)

\(n_{O_2}=\dfrac{2,24}{22,4}=0,1mol\)

\(2X+O_2\underrightarrow{t^o}2XO\)

\(\dfrac{13}{X}\)     0,1

\(\Rightarrow\dfrac{13}{X}=0,1\cdot2\Rightarrow X=65\)

Vậy X là kẽm Zn.

\(m_{ZnO}=0,2\cdot81=1,62g\)

\(n_{O_2}=\dfrac{2,24}{22,4}=0,1\left(mol\right)\)

PTHH: 2R + O₂ --to--> 2RO

          0,2   0,.1

=> \(M_R=\dfrac{13}{0,2}=65\left(\dfrac{g}{mol}\right)\)

=> R: Zn