Question

Intr-un pahar Berzelius cu 225g apa se adauga 25g CuSO4 5H2O. In alt pahar Erlenmeyer cu 50g solutie NaOH de concentratie 10% se adauga 2,3g sodiu .                              Calculati:a)concentratia procentuala a solutiei obtinute in paharul Berzelius                                              b)concentratia procentuala a solutiei obtinute in paharul Erlenmeyer                                         c)cantitatea de precipitat obtinuta la amestecarea solutiilor din cele doua pahare.    Se dau:ZAr=18 , ZS=16 , ZNa=11 , ZK=19 , ZCl=17 , AK=39 , ACl=35,5 , ACu=64 , As=32 , AO=16 , AH=1 , ANa=23 , NA=6,0225 ·10²³

Answer 1

a) Masa molara CuSO₄*5H₂O=64+32+64+90=250g/mol
250g CuSO₄*5H₂O................................160gCuSO₄
25g CuSO₄*5H₂O........................................x
x=25*160/250=16g CuSO₄⇒9g H₂O
masa de substanta=9+225+16=250g
c=md*10/ms
c=16*100/250
c=6.4%

b) c₁=md₁*100/ms₁
md₁=c₁*ms₁/100
md₁=10*50/100
md₁=5g

md final=5+2.3=7.3g
ms final=50+2.3=52.3g

c final=7.3*100/52.3
c final=13.95%

c) CuSO₄+2NaOH=Cu(OH)₂+Na₂SO₄
precipitatul=Cu(OH)₂
Masa molara CuSO₄=160g/mol
Masa molara Cu(OH)₂=64+2*16+2*1=98g/mol
y=masa de Cu(OH)₂ obtinuta
y=16*98/160=9.8g Cu(OH)₂