Question

Prin dizolvarea a 0,39 g aliaj de magneziu si aluminiu in 50 g solutie HCl 5%, se degaja 448 ml de gaz, masurat in conditii normale. Sa se calculeze:
a) Compozitia procentuala a aliajului;
b) Compozitia procentuala a solutiei rezultate.

Va rog repede! Dau coroana!!

Answer 1

Al + 3 HCl => AlCl3 + 3/2 H2
Mg + 2 HCl => MgCl2 + H2
27 g Al..............3/2*22,4 l H2
x g Al.....................x' l H2
=>33.6x = 27x' => x' = 33.6x/27
24 g Mg..............22,4 l H2
y g Mg.....................y' l H2
=>22,4y = 24y' => y' = 22,4y/24
x+y = 0.39
x'+y' = 0,448
x = 0,39 - y
=> 33,6*(0,39-y)/27 + 22,4y/24 = 0.448 (*24, *27)
=> 24*33,6*0,39 - 24*33,6*y + 22,4y*27 = 0,448*24*27
=> 314.496 - 806.4y + 604.8y = 290.304
=> 201.6y = 24,192 => y = 0.12 g Mg
m Al = 0,39 - 0,12 = 0,27 g Al
% Al = m Al/m aliaj * 100 = 0,27/0.39 * 100 = 69.23%
% Mg = m Mg/m aliaj * 100 = 0,12/0.39 * 100 = 30.76%
24 g Mg.........2*36.5 g HCl
0,12 g Mg...........x g HCl
x = 0,365 g HCl
227 g Al.........3*36.5 g HCl
0,27 g Al...........x g HCl
x = 1.095 g HCl
m HCl consumat = 1,095+0,365 = 1,46 g HCl
c = md/ms * 100 => md = ms*c/100 = 50*5/100 = 2.5 g HCl
m exces = 2,5 - 1,46 = 1.04 g HCl
c = md/ms * 100 = 1,04/50 * 100 = 2.08%