Question

DAU COROANA IMI TREBE URGENT!
1)Sa se afle c. solutiei obtinuta prin: adaugarea de apa in 600g solutie c=30% pana se obtin o mie de g solutie aflati si cantitatea de apa adaugata
2)Aflati c. obtinuta prin adaugarea de 20g subst. la 120g solutie c=45%

Answer 1

1)

ms1 = 600 g , c%1 = 30% , ms2 = 1000 g

c% = mdx100/ms

=> m.apa adugata = ms2 - ms1 = 1000 - 600 = 400 g

md = c1xms1/100 = 30x600/100 = 180 g

=> c%2 = mdx100/ms2 = 180x100/1000 = 18%

2)

ms1 = 120 g , c%1 = 45% , md2 = 20 g

stim ca c% = mdx100/ms

=> md1 = ms1xc1/100 = 120x45/100 = 54 g

md.tot = md1 + md2 = 54 + 20 = 74 g

ms.tot = ms1 + md2 = 120 + 20 = 140 g

=> c%2 = md.totx100/ms.tot

=> c2% = 74x100/140 = 52,86%