câu a$\underset{2x}{2AgNO_3} + \underset{x}{Fe} \longrightarrow \underset{x}{Fe(NO_3)_2} + \underset{2x}{2Ag}$
$\underset{2y}{2AgNO_3} + \underset{y}{Cu} \longrightarrow \underset{y}{Cu(NO_3)_2} + \underset{2y}{2Ag}$
$\Rightarrow m$chất rắn tăng$= m_{Ag}-m_{ Fe} + m_{Ag}-m_{Cu} $
$\Leftrightarrow 37,2-13,8 = 216x-56x+216y-64y$
$\Leftrightarrow 160x + 152y = 23,4 (1) $
2Fe(NO3)2 2Fe(OH)2 Fe2O3
x x 0,5x
=> =>
Cu(NO3)2 Cu(OH)2 CuO
y y y
=> 160.0,5x + 80y = 12 (2)
(1) và (2) => x= 0,075 y=0,075
=> %Fe = 46,67% %Cu=53,33%
câu b
nAgNO3 pư= 2x+2y = 0,3 mol
=> a= 0,3/ 0,75= 0,4M