Express 0.937 M in g L^-1.

1 Answer

enotechris's profile pic

enotechris | College Teacher | (Level 2) Senior Educator

Posted on

Molarity (M) is given as the number of moles of a solute in a liter (L) of solution.  To calculate the number of grams of a solute per liter of solution, you need to supply the molar mass of the solute, or at least specify what the compound is so that the molar mass can be calculated.  Without that, all you've got is 0.937 moles of something (we don't know what) in a liter of solution.

For argument's sake, let's assume the solute is common table salt, sodium chloride (NaCl).  The molar mass is calculated by taking the atomic mass units of each element found on the Periodic Table.  In this case,

Na = 22.99 amu, and CL = 35.45 amu, so a molecule of sodium chloride has an amu of:

NaCl = 22.99 + 35.45 = 58.44 amu.

The amu is also a count of the number of grams in a mole of a substance, so 58.44 amu is the same as 58.44 grams per mole of sodium chloride. Knowing that, the number of grams in the one liter solution can be calculated:

g = (0.937 moles) (58.44 g/mole) = 54.76 grams.