aHow many moles of chloride ions are in 0.2550 g of aluminum chloride?bWhat is the mass, in grams, of 7.70 x 10^20 molecules of caffeine, C8H10N4O2?please show work
Mass of an element or molecule is the formula weight in gramsFor example CO2 - carbon is 12g x1 and Oxygen is 16g x2, for a total of 44grams per mole 1 mole of ANYTHING is it's formula weight in grams Avogadro's number is the number of ATOMS in 1 mole of anything (6.022x10^23 atoms1 mole) for aluminum chloride you have to first write the empirical formula, then find the formula weightAl is +3, Cl is -1, so you have AlCl3Formula weight is Al (1)x 27 Cl (3)x 35.427+35.4+35.4+35.4 FW to get moles from grams, divide what you have (0.255g) by FW (X grams per mole) Grams cancels, leaving you with moles for (b), find the FW of caffeine C (8)x12, H (10)x1, N (4)x14, O (2)x16this will give you grams per mole (194 g/mol)Since you have 7.7 x10^20 molecules, you must divide by Avogradro's number, 6.022 x 10^23 (just by looking at the number, you have less than a mole - I got 0.00128 moles)Once you get this number, multiply it by grams/mole - moles cancels leaving you with grams (I got 0.25 g)
