U-world: Gen-Chem: Solution Chemistry #1

Based on the biological system described in the passage, how many millimoles of hydrogen ions are present in 10.0 mL of gastric acid(PH1)?

1.0 mmol **The molar concentration can be expressed as either moles/liter or scaled to millimoles/milliliter (mmol/mL).

What is the molar concentration of hydroxide in the duodenum (pH 6.0), where neutralization of the gastric acid leaving the stomach begins to take place?

1.0 × 10^−8 M **pH + pOH = 14.

By what factor is the hydronium ion concentration increased in the stomach lumen(PH1_) compared to the parietal cell(PH7)?

10^6 **The magnitude of [H3O+] changes by a power of 10 for each pH unit and is given by the expression Factor Δ[H3O+] = 10−ΔpH.

What is the estimated free energy change to transport H+ ions across the cell membrane from the parietal cell cytosol to the stomach lumen at a physiological temperature?

6.0kRT J/mol

Based on the passage, which of the following procedures would assist in separating an aqueous mixture of CuCl2 and CuSO4 salts at 90 °C?

Add Na2SO4 to the solution mixture(common ion effect) Cool the solution mixture to 5°C(temp. dependent) The wrong answers are: -Adding Cu(NO3)2 to the mixture would not be ideal for the separation, because this would increase the Cu2+ ion concentration, and both CuCl2 and CuSO4 contain a Cu2+ ion. Although CuSO4 would precipitate to a greater extent (because it is less soluble), some CuCl2 would still precipitate and result in a precipitate mixture. - Lowering the pH of the mixture by adding acid would be unhelpful in the separation because Cl− is not basic enough to react with the acid and shift the solubility equilibrium of CuCl2, and any SO42− reacting with H+ to form HSO4− would interfere with the precipitation of CuSO4 by shifting the equilibrium to the right and causing more CuSO4 to dissolve.

For the separation of a saturated aqueous mixture of CuF2 (Ksp = 1.6 × 10^−6) and BaF2 (Ksp = 3.0 × 10^−6), a lab technician chose to use the common ion effect to precipitate CuF2 from the solution rather than BaF2. Which of the following statements does NOT explain why precipitating CuF2 is the better choice for the separation procedure?

Adding F− as the common ion would cause CuF2 to precipitate The incorrect choices were: -CuF2 is less soluble and more responsive to small changes in common ion concentrations. -There are fewer moles of CuF2 to remove from the solution than moles of BaF2 -Precipitating BaF2 would require a greater number of common ions to be added to the solution

Which of the following will increase the amount of CuF2(s) that dissolves in water and raise the Cu2+(aq) concentration in the solution? (Note: Cu(OH)2 has a Ksp = 2.2 × 10^−20.)

Adding dilute nitric acid ** the fluoride ion is mildly basic, and this property can be exploited to disrupt the equilibrium because bases react with acids

Suppose that a research technician wants to separate an aqueous mixture of CuF2 and BaF2 (Ksp = 3.0 × 10−6) by precipitating CuF2 from the solution. What should be added to the solution to perform the separation?

Cu(NO3)2 **To separate a solution mixture of CuF2 and BaF2 by precipitating CuF2, Cu2+ ions can be introduced into the solution. The increased Cu2+ concentration disturbs the product side of the solubility equilibrium and causes it to shift toward the reactants (undissolved salt)

What happens to the pOH of the gastric acid entering the duodenum (pH 6.0) as a result of the introduction of bicarbonate ions from incoming pancreatic secretions?

The pOH decreases as [OH−] increases.

common ion effect and solubility

The presence of a common ion decreases the solubility of the salt.

Ksp

solubility product constant Ksp=[A+]^m[B-]^n do not include concentration of pure solid/liquids

If excess methylamine (CH3NH2) is added to a saturated aqueous CuF2 solution, the amount of CuF2 that dissolves will: (passage showed the reaction of amine adding to Cu2+)

increase **Adding ligands that can form soluble coordination complexes with metal ions in a solution can enhance the solubility of ionic salts

The most acidic

largest Ka, smallest pKa