Potassium bromide `KBr` contains `32.9%` potassium by mass. If `6.40 g` of bromine reacts with `3.60 g` of potassium, calculate the number of moles of potassium which combine with bromide to form `KBr`.

Explanation

Suppose mass of KBr = 100 g
Mass of potassium = 32.9 g
Mass of bromine = 67.1 g 67.1 g
67.1 g of bromine combine with potassium = 32.9 g .
`therefore 6.4` g of bromine will combine with potassium = `(32.9)/(67.1) xx 6.4 = 3.14 g`
Atomic mass of potassium = 39 u .
Moles of potassium which combine with bromine to form `=3.14/39 = 0.0805` mol