Question

Potassium chloride (KCl) is sometimes used to treat low blood potassium levels. Calculate the concentration of a saturated solution of potassium chloride at 20°C. Question continued-?

Hint: The formula for molarity, a common concentration unit, is M = moles/volume of solution expressed in units of mol/L. You will need to convert from grams of KCl to moles. Assume the volume of solution is 100 mL. Show your work!
Info: 36g of KCl is the max 100mL of water could hold at 20°C.

Answer 1

Molarity is the most convenient way to express concentration.

Mathematically, molarity is expressed as
`\frac{\text{mass of solute(g)}}{\text{gram molecular weight X Volume of solution (l)}}`

In present case,
mass of solute (KCl) = 36 g
molecular weight of KCl = 74.55 g/mol
volume of solution = 100 ml = 0.1 l

∴ Molarity =
`(36)/(74.55X0.1)`
= 4.829 M
Thus, conc. of saturated KCl at 20 oC is 4.829 M