How many molecules are contained in 0.254 mol of diarsenic trioxide

Which statement describes both homogeneous mixtures and heterogeneous mixtures?

Achemist 16 drop copper metal from copper chloride solution. the chemist place is 0.50 g of aluminum foil in a solution containing 0.75 g of copper (ii) chloride. a single replacement reaction takes place. which statement explains the maximum amount of copper that the chemist can extract using this reaction?

What is the percentage of hydrogen in nitrogen trihydride