\(n_K=\dfrac{7,8}{39}=0,2\left(mol\right)\\ a,2K+2H_2O\rightarrow2KOH+H_2\uparrow\\ n_{H_2}=\dfrac{0,2}{2}=0,1\left(mol\right)\\ V_{H_2\left(\text{đ}ktc\right)}=0,1.22,4=2,24\left(l\right)\\ b,n_{KOH}=n_K=0,2\left(mol\right)\\ m_{KOH}=0,2.56=11,2\left(g\right)\\ c,m_{\text{dd}sau}=m_K+m_{H_2O}-m_{H_2}\)

Nhưng chưa có KL nước?

Bài 1 : 

a. \(n_{Al}=\dfrac{10,8}{27}=0,4\left(mol\right)\)

\(n_{O_2}=\dfrac{16}{32}=0,5\left(mol\right)\)

b. PTHH : 4Al + 3O₂ -t^o> 2Al₂O₃

                 0,4       0,3       0,2

Xét tỉ lệ : \(\dfrac{0,4}{4}< \dfrac{0,5}{3}\) => Al đủ , O₂ dư

\(m_{O_2\left(dư\right)}=\left(0,5-0,3\right).32=6,4\left(g\right)\)

c. \(m_{Al_2O_3}=0,2.102=20,4\left(g\right)\)

Bài 2:

nFe = 11,2/56 = 0,2 (mol)

nHCl = 18,25/36,5 = 0,5 (mol)

PTHH: Fe + 2HCl -> FeCl2 + H2

LTL: 0,2 < 0,5/2 => HCl dư

nH2 (lt) = nFe = 0,2 (mol)

VH2 (lt) = 0,2 . 22,4 = 4,48 (l)

VH2 (tt) = 4,48 . 60% = 2,688 (l)

\(n_K=\dfrac{7,8}{39}=0,2\left(mol\right)\)

a) Pt : \(2K+2H_2O\rightarrow2KOH+H_2\)

           0,2                      0,2       0,1

b) \(V_{H2\left(dktc\right)}=0,1.22,4=2,24\left(l\right)\)

c) \(m_{KOH}=0,2.56=11,2\left(g\right)\)

d) 

\(C\%_{KOH}=\dfrac{11,2}{100}.100\%=11,2\%\)

 Chúc bạn học tốt

2Zn + O₂ --> 2ZnO

0,06 <-- 0,03 <----0,06 (mol)

n_ZnO = \(\dfrac{4,86}{81}\)= 0,06 (mol)

m_Zn = 0,06 . 65 = 3,9 (g)

VO2 = 0,03 . 22,4 = 0,672 (l)

2KClO₃ ----> 2KCl + 3O₂

0,02 <------------------- 0,03 (mol)

m_KClO3 = 0,02 . (39 + 35,5 + 16.3)

                = 2,45 (g)

Kiểm tra lại dùm, thank you

a,PTHH: 2Zn+O2−to−>2ZnO2Zn+O2−to−>2ZnO

Bảo toàn khối lượng

⇒mZn=mZnO−mO2=32,4−6,4=26(g)

b,

 Ta có: n_Zn = 6,565=0,1(mol)6,565=0,1(mol)

Theo phương trình, n_O2 = 0,12=0,05(mol)0,12=0,05(mol)

=> Thể tích khí Oxi: V_O2(đktc) = 0,05 x 22,4 = 1,12 (l)

c,

PTHH:2KClO3to→2KCl+3O2PTHH:2KClO3to→2KCl+3O2

nO2=VO222,4=5,0422,4=0,225(mol)nO2=VO222,4=5,0422,4=0,225(mol)

TheoTheo PTHH,PTHH, tacó:tacó:

nKClO3=23nO2=23.0,225=0,15(mol)nKClO3=23nO2=23.0,225=0,15(mol)

mKClO3=nKClO3.MKClO3=0,15.122,5=18,375(g)mKClO3=nKClO3.MKClO3=0,15.122,5=18,375(g)

Vậy ...

Ko b đúng ko nữa.

2K+2H2O->2KOH+H2

0,1-----0,1-----0,1---0,05

n K=0,1 mol

=>m KOH=0,1.56=5,6g

=>VH2=0,05.22,4=1,12l

2H2+O2-to>2H2O

0,05--------------0,05

n O2=0,2 mol

=>O2 dư

=>mH2O=0,05.18=0,9g

a)

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

b) $n_{KMnO_4} = \dfrac{79}{158} = 0,5(mol)$

Theo PTHH : $n_{O_2} = \dfrac{1}{2}n_{KMnO_4} = 0,25(mol)$
$\Rightarrow V_{O_2} = 0,25.22,4 = 5,6(lít)$

c) $n_P = \dfrac{3,1}{31} = 0,1(mol)$

$4P + 5O_2 \xrightarrow{t^o} 2P_2O_5$
Ta thấy : $n_P : 4 < n_{O_2} :5$ nên $O_2$ dư

$n_{P_2O_5} = \dfrac{1}{2}n_P = 0,05(mol)$
$m_{P_2O_5} = 0,05.142 = 7,1(gam)$

\(a) Zn +2 CH_3COOH \to (CH_3COO)_2Zn + H_2\\ b) n_{H_2} = n_{Zn} = \dfrac{13}{65} = 0,2(mol)\\ V_{H_2} = 0,2.22,4 = 4,48(lít)\\ n_{CH_3COOH} = 2n_{Zn} = 0,4(mol) \Rightarrow V_{dd\ CH_3COOH} = \dfrac{0,4}{1} = 0,4(lít)\\ c) C_2H_5OH + O_2 \xrightarrow{men\ giấm} CH_3COOH + H_2O\\ n_{C_2H_5OH\ pư} = n_{CH_3COOH} = 0,4(mol)\\ m_{C_2H_5OH\ cần dùng} = \dfrac{0,4.46}{90\%} = 20,44(gam)\)

nAl=8,1/27=0,3mol           ;nH2SO4=53,9/98=0,55mol

ta có pt    :   2Al+3H2SO4---->Al2(SO4)3+3H2

Trước p/u:  0,3mol    0,55mol

p/u       :       0,3mol    0,45mol

Saup/u:       0mol       0,1mol      0,15mol     0,45mol

=>H2SO4 dư

mH2SO4 dư =0,1.98=9,8g

b,mAl2SO43 =0,15.294=44,1g

c, mH2=0,45.2=0,9g

   V H2=0,45.22,4=10,08l