Áp dụng ĐLBTKL ta có:

m_Zn+m_O=m_ZnO

=>m_O=18,8-11,2=7,6(g)

n_O=0,475(mol)

n_O2=0,475/2=0,2375(mol)

V_O2=0,2375.22,4=5,32(lít)

Vkk=5,32.5=26,6(lít)

pthh

2Zn+O2----> 2 ZnO

câu b sai đề rồi

ví :

áp dụng định luật bảo toàn khối lượng :

m O2=m ZnO-mZn=7,6 g

n O2=0,2375 mol

theo pthh thì n Zn=2.0,2375=0,475 mol

theo đề ra thì n Zn=56/325 mol

=> sai đề

\(Zn+O_2\rightarrow ZnO\)

Theo định luật bảo toàn khối lượng ta có : \(m_{Zn}+m_{O_2}=m_{ZnO}\)

\(=>11,2+m_{O_2}=18,8=>m_{O_2}=18,8-11,2=7,6\left(g\right)\)

Lượng không khí vừa đủ đốt là : \(m_{kk}=m_{O_2}:\frac{1}{5}=7,6:\frac{1}{5}=38\left(g\right)\)

a, \(2Zn+O_2\underrightarrow{t^o}2ZnO\)

b, \(n_{Zn}=\dfrac{13}{65}=0,2\left(mol\right)\)

Theo PT: \(n_{O_2}=\dfrac{1}{2}n_{Zn}=0,1\left(mol\right)\Rightarrow V_{O_2}=0,1.22,4=2,24\left(l\right)\)

\(\Rightarrow V_{kk}=5V_{O_2}=11,2\left(l\right)\)

c, \(2KMnO_4\underrightarrow{t^o}K_2MnO_4+MnO_2+O_2\)

Theo PT: \(n_{KMnO_4}=2n_{O_2}=0,2\left(mol\right)\Rightarrow m_{KMnO_4}=0,2.158=31,6\left(g\right)\)

ta có :

2Mg+O2-to>2MgO

x--------0,5x

2Zn+O2-to>2ZnO

y-------0,5y

=>\(\left\{{}\begin{matrix}24x+65y=14,58\\0,5x+0,5y=0,15\end{matrix}\right.\)

=>x=0,12 mol ,y=0,18 mol

=>%mMg=\(\dfrac{0,12.24}{14,58}100\)=19,753%

=>%mZn=80,247%

\(n_{O_2}=\dfrac{4,8}{32}=0,15mol\)

Gọi \(\left\{{}\begin{matrix}n_{Mg}=x\\n_{Zn}=y\end{matrix}\right.\)

\(2Mg+O_2\rightarrow\left(t^o\right)2MgO\)

  x        1/2 x                       ( mol )

\(2Zn+O_2\rightarrow\left(t^o\right)2ZnO\)

  y       1/2 y                         ( mol )

Ta có:

\(\left\{{}\begin{matrix}24x+65y=14,58\\\dfrac{1}{2}x+\dfrac{1}{2}y=0,15\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}x=0,12\\y=0,18\end{matrix}\right.\)

\(\rightarrow\left\{{}\begin{matrix}m_{Mg}=0,12.24=2,88g\\m_{Zn}=0,18.65=11,7g\end{matrix}\right.\)

\(\rightarrow\left\{{}\begin{matrix}\%m_{Mg}=\dfrac{2,88}{14,58}.100=19,75\%\\\%m_{Zn}=100\%-19,75\%=80,25\%\end{matrix}\right.\)

\(n_{O_2}=\dfrac{4,8}{32}=0,15\left(mol\right)\) 
gọi số mol Mg : a , số mol Zn : b (a,b>0) 
pthh : \(2Mg+O_2\underrightarrow{t^o}2MgO\) 
         a          \(\dfrac{1}{2}a\) 
         \(2Zn+O_2\underrightarrow{t^o}2ZnO\) 
         b         \(\dfrac{1}{2}b\) 
mà 24a + 65b=14,58  
có : \(\dfrac{1}{2}a+\dfrac{1}{2}b=0,15\) 
=> a = 0,12 ( mol ) , b=0,18 (mol) 
=> \(\%m_{Zn}=\dfrac{0,18.65}{14,68}.100\%=79,7\%\\ \%m_{Mg}=100\%-79,7\%=20,3\%\)

\(n_{O_2}=\dfrac{6,72}{5.22,4}=0,06\left(mol\right)\\ PTHH:2Zn+O_2\underrightarrow{t^o}2ZnO\\ Mol:0,03\leftarrow0,06\rightarrow0,03\\ \rightarrow\left\{{}\begin{matrix}a=0,03.65=1,95\left(g\right)\\x=0,03.81=2,43\left(g\right)\end{matrix}\right.\)

\(PTHH:2KMnO_4\underrightarrow{t^o}K_2MnO_4+MnO_2+O_2\uparrow\)

                     0,12                                         0,06

\(\rightarrow m_{KMnO_4}=0,12.158=18,96\left(g\right)\)

PTHH: \(Zn+\dfrac{1}{2}O_2\xrightarrow[]{t^o}ZnO\)

Bảo toàn khối lượng: \(m_{O_2}=m_{ZnO}-m_{Zn}=1,6\left(g\right)\)

a. \(2Zn+O_2\rightarrow2ZnO\)

b.\(m_{Zn}+m_{O_2}\rightarrow m_{ZnO}\)

\(\Rightarrow6,5+m_{O_2}=8,1\)

\(\Rightarrow m_O=8,1-6,5=1,6\)

a) C + O₂ --t^o--> CO₂

b) \(n_C=\dfrac{24}{12}=2\left(mol\right)\)

=> n_CO2 =2 (mol)

=> m_CO2 = 2.44 = 88(g)

c)

n_O2 = 2(mol)

=> V_O2 = 2.22,4 = 44,8 (l)

=> V_kk = 44,8.5=224(l)

a)

$C + O_2 \xrightarrow{t^o} CO_2$
b)

$n_{CO_2} = n_C = \dfrac{24}{12} = 2(mol)$
$m_{CO_2} = 2.44 = 88(gam)$
c)

$n_{O_2} = n_C = 2(mol)$
$V_{O_2} = 2.22,4 = 44,8(lít)$
$V_{không\ khí} =5 V_{O_2} = 44,8.5 = 224(lít)$

a: \(C+O_2\rightarrow CO_2\)

b: \(n_C=\dfrac{24}{12}=2\left(mol\right)\)

\(\Leftrightarrow n_{CO_2}=2\left(mol\right)\)

\(\Leftrightarrow m_{CO_2}=2\cdot44=88\left(g\right)\)