A 0.040 M HCl solution is measured in the laboratory and has an osmotic pressure of 1.9 atm. What is the estimated osmotic pressure of gastric acid (approximated as 0.10 M HCl) under the same conditions?

Question

A 0.040 M HCl solution is measured in the laboratory and has an osmotic pressure of 1.9 atm.  What is the estimated osmotic pressure of gastric acid (approximated as 0.10 M HCl) under the same conditions?

Quizplus · Accepted Answer

11ecba2d_11f3_d5d1_a3bf_cb5b06f05dd7_MD0008_00 The diffusion of solvent across a semipermeable membrane from a solution of lower concentration into a solution of higher concentration during osmosis produces an osmotic pressure Π against the membrane, which is calculated by the relationship: 11ecba2d_11f3_d5d2_a3bf_1f5afd3394c1_MD0008_00 Although the osmotic pressure of the gastric acid relative to the laboratory HCl can be calculated by this relationship, it is not necessary to do so here. As shown by the equation, osmotic pressure is proportional to the concentration of the osmotically active solute. Accordingly, because iRT is the same for both samples, the calculation can be performed as a proportion relating the gastric acid to the laboratory acid as follows: 11ecba2d_11f3_d5d3_a3bf_b5fc91c65a7a_MD0008_00 11ecba2d_11f3_d5d4_a3bf_492e0edd82a0_MD0008_00 11ecba2d_11f3_fce5_a3bf_4f6079f7c21f_MD0008_00 Because the gastric acid concentration is 2.5 times greater than that of the laboratory acid, the osmotic pressure of the gastric acid is also 2.5 times greater than that of the laboratory acid, giving the gastric acid an osmotic pressure of 4.8 atm. (Choice A) Multiplying the concentration of the gastric acid by the osmotic pressure of the laboratory acid yields a value of 0.19 with incorrect units of atm·M. This value must also be divided by the laboratory acid concentration. (Choice B) If the temperature of 24 °C is not converted to the Kelvin scale (24 °C + 273 = 297 K), a calculated value of 0.40 atm·°C/K (with incorrect units) is obtained. (Choice C) Using a value of i = 1 does not account for the dissociation of HCl into two ions (H⁺ and Cl⁻). This yields a calculated result of 2.4 atm, which is only half of the correct value. Educational objective: The diffusion of solvent across a semipermeable membrane during osmosis produces an osmotic pressure against the membrane, which is directly proportional to the concentration of the osmotically active solute in solution.

A 0040 M HCl Solution Is Measured in the Laboratory and and Has