Acid-Base Chemistry Quiz

Show how is the Henderson-Hasselbalch equation derived.

Answer explanation

The Henderson-Hasselbalch equation is derived from the acid dissociation constant (Ka) expression. It relates pH, pKa, and the ratio of the concentrations of the conjugate base and acid, showing how buffer solutions maintain pH.

What is the pH of the solution after mixing 60 ml of 0.2 M KOH with 40 ml of 0.1 M HNO3?

Answer explanation

First, calculate moles of KOH: 0.2 M * 0.060 L = 0.012 moles. For HNO3: 0.1 M * 0.040 L = 0.004 moles. KOH is in excess (0.012 - 0.004 = 0.008 moles). Total volume = 100 ml. pOH = -log(0.08) = 1.1, so pH = 14 - 1.1 = 12.9.

Define acids using the Brønsted-Lowry theory.

Answer explanation

According to the Brønsted-Lowry theory, acids are defined as substances that donate protons (H+) to other substances in a chemical reaction.

Write an equation for the reaction between nitric acid and water. State the role of water in this reaction, using the Brønsted-Lowry definition.

Answer explanation

The equation for the reaction is HNO3 + H2O ⇌ H3O+ + NO3-. In this reaction, water acts as a Brønsted-Lowry base, accepting a proton (H+) from nitric acid, which is a Brønsted-Lowry acid.

Determine the pH of a 0.002M nitric acid solution. (note: HNO3 is a strong acid and completely ionizes in solution)

Answer explanation

To find the pH of a 0.002M nitric acid solution, use the formula pH = -log[H+]. Since HNO3 is a strong acid, it fully dissociates, so [H+] = 0.002M. Thus, pH = -log(0.002) = 2.70.

Calculate the number of moles for each solution: i.Solution A ii.Solution B

Answer explanation

To calculate moles, use the formula: moles = mass (g) / molar mass (g/mol). For Solution A and B, divide their respective masses by their molar masses to find the number of moles.

If solution A and B is mixed, write the remaining number of moles after the reaction. i.Solution A ii.Solution B iii.Write the chemical reaction of the following reaction. CH3COOH + KOH

Answer explanation

The reaction CH3COOH + KOH produces CH3COOK + H2O. If both solutions are mixed in equal moles, the remaining moles of CH3COOH and KOH will be zero, as they completely react to form the products.

Determine the molarities of solution A and the salt formed.

Answer explanation

To find the molarities of solution A and the salt, use the formula M = moles/volume. Calculate moles from the mass of solute and divide by the solution's volume in liters. The salt's molarity is derived from the stoichiometry of the reaction.

Determine the pH of a solution made by mixing 0.05 moles of acetic acid, CH3COOH, with 0.03 moles of potassium hydroxide, KOH, and diluting to a total volume of 1L. Given that pKa = 4.76.

Answer explanation

Mixing 0.05 moles of acetic acid with 0.03 moles of KOH results in 0.02 moles of acetic acid remaining. Using the Henderson-Hasselbalch equation, pH = pKa + log([A-]/[HA]), we find pH = 4.76 + log(0.03/0.02) = 4.85.

Write an expression for the dissociation constant Ka of propanoic acid, CH3CH2COOH.

Answer explanation

The dissociation constant Ka for propanoic acid (CH3CH2COOH) is expressed as Ka = [H+][CH3CH2COO-] / [CH3CH2COOH], where [H+] is the concentration of hydrogen ions, [CH3CH2COO-] is the concentration of the conjugate base, and [CH3CH2COOH] is the concentration of the acid.