Question

Ringer's lactate, a solution containing several different salts, is often administered intravenously for the initial treatment of trauma patients. One liter of Ringer's lactate continas 0.102 mole of sodium chloride, 4.0 × 10^-3 mole of potassium chloride, 1.5 × 10^-3 mole of calcium chloride, and 2.8 × 10^-2 mole of sodium lactate. Determine the osmotic pressure (in atm) of the solution at normal body temperature (37^oC). Assume no ion pairing. (The formula of the lactate ion is HO-CH(CH₃)-COO^-.)

Answer 1

NaCl moles (n1) = 0.102

i value for NaCl = 2

mole of potassium chloride (n2)= 4.0 × 10^-3

i value for NaCl = 2

mole of calcium chloride (n3)= 1.5 × 10^-3

i value for CaCl2 = 3

mole of sodium lactate.(n4) = 2.8 × 10^-2

i value for sodium lactate = 2

i₁ n₁ + i₂ n₂+ i₃ n₃ +i₄ n₄ = (0.102 x 2 + 4 x 10^-3 x 2 + 1.5 x 10^-3 x 3+ 2.8 x 10^-2 x 2)

                          = 0.2725

S = 0.0821 L- atm / mol .K

T= 37 + 273 = 310 K

V = 1 Litre

osmotic pressure = ( i₁ n₁ + i₂ n₂+ i₃ n₃ +i₄ n₄ ) S T / V

                            = 0.2725 x 0.0821 x 310 / 1

                            = 6.94 atm