Since molecules of potassium contain only single potassium atoms, molecules of iodine contain two atoms, and moles of potassium iodide contain one atom of each element, 2.5 moles of iodine are needed to react completely with 5 moles of potassium.
The formula for potassium chloride is KCl; one atom of potassium attaches to one atom of chlorine. Chlorine gas is diatomic (Cl2); thus, if there are 100 atoms of potassium to react, 100 atoms of chlorine will be needed. Therefore, 50 molecules of chlorine gas will be used.
One advantage of a lithium battery is that is has a very high energy density and capacity that other batteries do not. Thus, a relatively small amount of lithium is needed to power a relatively large device.
Lithium can never be formed from hydrogen chloride in a chemical reaction, because lithium, hydrogen, and chlorine are all distinct elements, none of which can be converted any others by chemical means.