Question

Cine ma poate ajuta la aceasta tema? (Fara primele doua exercitii.) Multumesc!

Answer 1

5.
se porneste de o sol. H3PO4 cu masa ms1 si c1=40% si prin diluare se ajunge la ms2=400g sol si c2=10%
md2=ms2*c2/100=40g
md1=md2
m1=md1*100/c1=40*100/40=100g

6.
Mg(OH)2+2HCl----->MgCl2+ 2H2O

Cm=niu/Vs ==>nr.moli (niu)=0,001moli Mg(OH)2
din ec. reactiei:
58g mg(OH)2......2moliHCl
x g .......................0,001moli HCl
x=0,029 g Mg(OH)2 (md)
ms=md*100/c=......

7.
la 60 gr.c
139g sol......39g CuSO4
400g sol.........x  x=112,23 g CuSO4
deci 400g sol contine 112,23g CuSO4 si 287,77 g H2O din care prin racire se depun x g cristalohidrat
250 g ch.....160g CuSO4..................90g H2O
xg ch..........160x/250 g CuSO4..........90x/250g H2O
la 20gr.C masa de sare anhidra este
112,23-160x/250
si masa de apa este 287,77-90x/250

100g H2O.................21g sare
(287,77-90x/250)......(112,23-60x/250)
de aici se calculeaza x=...........