Question

a) Ce masa de zahar este dizolvata in 400g de sirop de concentratie 60%?

b) Ce masa de solutie de concentratie de 25% se obtine prin dizolvarea a 40g de soda caustica in apa?

c) Ce masa de var stins se gaseste in 250g de solutie apa de var cu concentratia 4%

d) Determina concentratia solutiei obtinute prin dizolvarea a 120g sare de bucatarie cu puritatea 90% in 392g de apa daca impuritatile nu sunt solubile.

Answer 1

a)

ms = 400g

c= 60%

-----------------------/--

md = ? g

---------------------//--

c = mdx100/ms

=> md = msxc%/100 = 400x60/100 = 240 g zahar

b)

md = 40 g

c = 25%

---------------------/--

ms = ? g

--------------------//--

c = mdx100/ms

=> ms = mdx100/c% = 40x100/25 = 160 g sol

c)

idem a)

d)

m.impura = 120 g

p% = 90%

m.apa = 392 g

----------------------------/---

c = ?%

--------------------------//--

120 g sare impura ...................... 100%

md sare pura ............................. 90%

= 108 g

c = mdx100/ms

ms = md + m.apa = 108 + 392 = 500 g

=> c = 108x100/500 = 21,6%