Question

prin aducere unei cantitati de soda paste 50gde concentratie 20% se obtine o noua solutie de concentratie 23% ce masura de soda a fost folosita

Answer 1

ms1 = 50 g , c%1 = 20%

c%2 = 23% si stim ca c% = mdx100/ms

=> md1 = ms1xc%1/100 = 50x20/100 = 10 g

md2 = md1 + a , a = masa de soda adaugata

=> ms2 = ms1 + a

=> 23 = (10+a)x100/(50+a)

=> 23(50+a) = 1000 + 100a

=> 1150 + 23a = 1000 + 100a

=> a = 1,95 g soda adugata

facem proba:

ms2 = ms1+a = 51,95 g

md2 = md1+a = 11,95 g

=> c%2 = 11,95x100/51,95 = 23%........deci se probeaza