help with 1-3 please

SHOW ALL WORK USING UNITS Round the answers to the appropriate number of sig 1 mol = 22.4 L for a gas at STP ( 1 atmosphe figures. 1. How many atoms are in 4.5 moles of Na? 4.9 molestie molesta 2. How many moles are present if you have 4.67 x 10** molecules of carbon dioxide? 3. 24 atoms of sodium = moles of sodium atoms 4. 2.89 x 10 molecules of ammonia = 23 moles of ammonia molecules 5. 15 moles of arsenic atoms - atoms of arsenic 10 moles of barium atoms = atoms of barium 6. 4.00 x Why did Prof. Avogadro choose 6.022 x 1023? 12.01 grams of carbon atoms contain 6.022 x 1023 atoms of carbon 1.008 grams of hydrogen atoms contain 6.022 x 1023 atoms of hydrogen 16.00 grams of oxygen atoms 6.022 x 1023 atoms of oxygen How many grams of carbon are in a mole of carbon atoms? Where have you seen this number