Question

A biochemist carefully measures the molarity of sucrose in 30.3 mL of cell growth medium to be 56.8 mM. Unfortunately, a careless graduate student forgets to cover the container of growth medium and a substantial amount of the solvent evaporates. The volume of the cell growth medium falls to 4.59 mL. Calculate the new molarity of sucrose in the cell growth medium. Round each of your answers to 3 significant digits. mM

Answer 1

Given,

The initial volume of cell growth medium = 30.3 mL x ( 1L /1000 mL) = 0.0303 L

The initial molarity of sucrose solution = 56.8 mM x ( 1 M / 1000 mM) = 0.0568 M

The new volume of cell growth medium = 4.59 mL x ( 1 L/1000 mL) = 0.00459 L

Calculating the number of moles of sucrose from the initial volume and initial molarity,

= 0.0303 L x 0.0568 M

= 0.001721 mol sucrose

Now, the new molarity is,

= 0.001721 mol / 0.00459 L

= 0.37495 M

Converting M to mM,

= 0.37495 M x ( 1000 mM/ 1 M)

= 374.95 mM

= 375 mM [ 3 S.F]