Starting with the first one
color(blue)((1)) One mole of any substance contains exactly 6.022 * 10^(23) molecules or atoms of that substance - this is known as Avogadro's number. Since you have less than 1 mole of ethanol, CH_3OH, you'll get less that 6.022 * 10^(23) molecules of ethanol.
3.10 * 10^(-2)cancel("moles") * (6.022 * 10^(23)"molec.")/(1cancel("mole")) = color(green)(1.87 * 10^(22)"molec.")
color(blue)((2)) To get the number of carbon atoms present in that much butane, you must first determine how many molecules of butane you're dealing with. Since the molecular formula of butane is C_4H_10, you'll get 4 carbon atoms for every 1 molecule of butane.
0.570cancel("moles") * (6.022 * 10^(23)"molec.")/(1cancel("mole")) = 3.43 * 10^(23)"molec."
Therefore, you get
3.43 * 10^(23)cancel("molecules") * ("4 C atoms")/(1cancel("molecule")) = color(green)(1.37 * 10^(24)"atoms"
Questions color(blue)((3)) and color(blue)((4)) are identical to the first two, the only difference being the actual values you have to work with.
For question color(blue)((4)), the number of atoms of oxygen in aluminium nitrate will be 9. You get 3 oxygen atoms from each of the 3 nitrate anions that make up the compound.
