\(n_K=\dfrac{5,85}{39}=0,15\left(mol\right)\)

PTHH: 2K + 2H₂O --> 2KOH + H₂

_____0,15------------->0,15-->0,075

=> V_H2 = 0,075.22,4  =1,68(l)

mdd = 5,85 + 100 - 0,075.2 = 105,7(g)

=> \(C\%=\dfrac{0,15.56}{105,7}.100\%=7,95\%\)

\(a.Ba+H_2O\rightarrow Ba\left(OH\right)_2+H_2\\ b.n_{Ba}=\dfrac{1,37}{137}=0,01\left(mol\right)\\ n_{H_2}=n_{Ba}=0,01\left(mol\right)\\ \Rightarrow m_{H_2}=0,01.2=0,02\left(g\right)\\ c.n_{Ba\left(OH\right)_2}=n_{Ba}=0,01\left(mol\right)\\ \Rightarrow m_{Ba\left(OH\right)_2}=0,01.171=1,71\left(g\right)\\ d.m_{ddsaupu}=1,37+72-0,02=73,35\left(g\right)\\ C\%_{Ba\left(OH\right)_2}=\dfrac{1,71}{73,35}.100=2,33\%\)

a) PTHH: \(Fe+2HCl\rightarrow FeCl_2+H_2\uparrow\)  (1)

                \(Mg+2HCl\rightarrow MgCl_2+H_2\uparrow\)  (2)

b) Dựa vào đề, ta thấy chắc chắn HCl dư

Ta có: \(\Sigma n_{H_2}=\dfrac{4,48}{22,4}=0,2\left(mol\right)\)

Gọi số mol của Fe là \(a\) \(\Rightarrow n_{H_2\left(1\right)}=a\)

Gọi số mol của Mg là \(b\) \(\Rightarrow n_{H_2\left(2\right)}=b\)

Ta lập được hệ phương trình:

\(\left\{{}\begin{matrix}56a+24b=8\\a+b=0,2\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}a=0,1\\b=0,1\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}m_{Fe}=56\cdot0,1=5,6\left(g\right)\\m_{Mg}=24\cdot0,1=2,4\left(g\right)\end{matrix}\right.\)

\(\Rightarrow\left\{{}\begin{matrix}\%m_{Fe}=\dfrac{5,6}{8}\cdot100\%=70\%\\\%m_{Mg}=30\%\end{matrix}\right.\)

c) Theo các PTHH: \(n_{FeCl_2}=n_{MgCl_2}=n_{Fe}=n_{Mg}=0,1mol\)

\(\Rightarrow\left\{{}\begin{matrix}m_{FeCl_2}=0,1\cdot127=12,7\left(g\right)\\m_{MgCl_2}=0,1\cdot95=9,5\left(g\right)\end{matrix}\right.\) \(\Rightarrow m_{muối}=22,2\left(g\right)\)

d) Ta có: \(\Sigma n_{HCl}=\dfrac{500\cdot16\%}{36,5}=\dfrac{160}{73}\left(mol\right)\)

\(\Rightarrow n_{HCl\left(dư\right)}=\dfrac{654}{365}\left(mol\right)\) \(\Rightarrow m_{HCl\left(dư\right)}=\dfrac{654}{365}\cdot36,5=65,4\left(g\right)\)

Mặt khác: \(m_{dd}=m_{hh}+m_{ddHCl}-m_{H_2}=507,6\left(g\right)\)

\(\Rightarrow\left\{{}\begin{matrix}C\%_{FeCl_2}=\dfrac{12,7}{507,6}\cdot100\%\approx2,5\%\\C\%_{MgCl_2}=\dfrac{9,5}{507,6}\cdot100\%\approx1,87\%\\C\%_{HCl\left(dư\right)}=\dfrac{65,4}{507,6}\cdot100\%\approx12,88\%\end{matrix}\right.\)

\(a,n_{K_2O}=\dfrac{18,8}{94}=0,2\left(mol\right)\)

PTHH: K₂O + H₂O ---> 2KOH

           0,2--------------->0,4

b, \(V_{ddKOH}=\dfrac{0,4}{2}=0,2\left(l\right)\)

c, dd sau phản ứng là QT chuyển sang màu xanh vì KOH là dd bazơ

nHCl=0,3.2=0,6(mol)

a) PTHH: CuO +2 HCl -> CuCl2 + H2O

0,3_______________0,6___0,3(mol)

b) mCuO=0,3.80=24(g)

c) VddCuCl2=VddHCl=0,3(l)

=>CMddCuCl2=0,3/0,3=1(M)

d) m(muối)=0,3.135=40,5(g)

a, \(n_{Na}=\dfrac{3,45}{23}=0,15\left(mol\right)\)

PT: \(2Na+2H_2O\rightarrow2NaOH+H_2\)

Theo PT: \(n_{NaOH}=n_{Na}=0,15\left(mol\right)\Rightarrow C_{M_{NaOH}}=\dfrac{0,15}{0,2}=0,75\left(M\right)\)

b, \(n_{H_2}=\dfrac{1}{2}n_{Na}=0,075\left(mol\right)\)

\(n_{O_2}=\dfrac{0,96}{32}=0,03\left(mol\right)\)

PT: \(2H_2+O_2\underrightarrow{t^o}2H_2O\)

Xét tỉ lệ: \(\dfrac{0,075}{2}>\dfrac{0,03}{1}\), ta được H₂ dư.

Theo PT: \(n_{H_2O}=2n_{O_2}=0,06\left(mol\right)\Rightarrow m_{H_2O}=0,06.18=1,08\left(g\right)\)

a) \(n_{Fe_2O_3}=\dfrac{16}{160}=0,1\left(mol\right)\)

PTHH: Fe₂O₃ + 6HCl → 2AlCl₃ + 3H₂O

Mol:       0,1         0,6         0,2

\(m_{ddHCl}=\dfrac{0,6.36,5.100}{14,6}=150\left(g\right)\)

b) m_{dd sau pứ} = 16 + 150 = 166 (g)

\(C\%_{ddFeCl_3}=\dfrac{0,2.162,5.100\%}{166}=19,58\%\)