Question: how many moles of electrons will weigh 1 kg?
Answer: Mass of an electron= 9.1 x 10^-31 Kg. Avagadro Number=6.022 x^10^23. So 1Kg of electrons contain 1.825 x10^6 moles of electrons. 1.8x10^6 moles of electrons weigh 1 kg.