Question

How did Avogadro know that a mole is exactly equals to 6.022×10²³ Particles?​

Answer 1

Avogadro's number is an absolute number: there are 6.022×1023 elementary entities in 1 mole. This can also be written as 6.022×1023 mol-1. The mass of one mole of a substance is equal to that substance's molecular weight.