raspunsul corect este A
NA = 6.023 x 10^23 atomi/mol
adica intr-un mol de element = 6.023 x 10^23 atomi
a)
71 g Cl = 2 mol Cl => 2x 6.023 x 10^23 =12,046x10²³ atomi
2 mol Na = 2 x 6.023 x 10^23 = 12,046x10²³ atomi
32 g O = 2 mol O=> 2 * 6.023 x 10^23 = 12,046x10²³ atomi