Open Question
What is the electron-dot structure and geometry of XeO3?
Ch.22 - The Main Group Elements
Chapter 22, Problem 164
Consider phosphorous acid, a polyprotic acid with the formula H3PO3. (a) Draw two plausible structures for H3PO3. For each one, predict the shape of the pH titration curve for the titration of H3PO3 (Ka1 = 1.0 * 10^-2) with aqueous NaOH. (b) For the structure with the H atoms in two different environments, calculate the pH at the first and second equivalence points, assuming that 30.00 mL of 0.1240 M H3PO3 (Ka2 = 2.6 * 10^-7) is titrated with 0.1000 M NaOH.
Verified step by step guidance1
Step 1: Draw two plausible structures for H3PO3. Consider the possible arrangements of hydrogen atoms and the central phosphorus atom, keeping in mind that phosphorous acid is a polyprotic acid, meaning it can donate more than one proton.
Step 2: Analyze the structures to determine the environments of the hydrogen atoms. Identify which hydrogen atoms are acidic and can be donated during the titration process.
Step 3: Predict the shape of the pH titration curve for each structure. Consider the number of acidic protons and their respective dissociation constants (Ka1 and Ka2) to understand how the pH changes as NaOH is added.
Step 4: Calculate the pH at the first equivalence point. Use the initial concentration of H3PO3 and the concentration of NaOH to determine the volume of NaOH needed to reach the first equivalence point, then apply the appropriate equilibrium expression to find the pH.
Step 5: Calculate the pH at the second equivalence point. Consider the remaining acidic hydrogen and its dissociation constant (Ka2) to determine the pH after the second equivalence point is reached.
Related Practice
Open Question
Of ammonia, hydrazine, and hydroxylamine, which reacts to the greatest extent with the weak acid HNO₂? Consult Appendix C for equilibrium constants.
Open Question
Write balanced equations for the reactions of (a) H3PO4 and (b) B1OH23 with water. Classify each acid as a Brønsted–Lowry acid or a Lewis acid.
Open Question
A 5.00 g quantity of white phosphorus was burned in an excess of oxygen, and the product was dissolved in enough water to make 250.0 mL of solution. (b) What is the pH of the solution? (c) When the solution was treated with an excess of aqueous Ca(NO3)2, a white precipitate was obtained. Write a balanced equation for the reaction and calculate the mass of the precipitate in grams. (d) The precipitate in part (c) was removed, and the solution that remained was treated with an excess of zinc, yielding a colorless gas that was collected at 20 °C and 742 mm Hg. Identify the gas, and determine its volume.
Open Question
A 500.0 mL sample of an equilibrium mixture of gaseous N2O4 and NO2 at 25 °C and 753 mm Hg pressure was allowed to react with enough water to make 250.0 mL of solution at 25 °C. You may assume that all the dissolved N2O4 is converted to NO2, which disproportionates in water, yielding a solution of nitrous acid and nitric acid. Assume further that the disproportionation reaction goes to completion and that none of the nitrous acid disproportionates. The equilibrium constant Kp for the reaction N2O4(g) ⇌ 2 NO2(g) is 0.113 at 25 °C. Ka for HNO2 is 4.5 * 10^-4 at 25 °C. (a) Write a balanced equation for the disproportionation reaction. (b) What is the molar concentration of NO2-, and what is the pH of the solution? (c) What is the osmotic pressure of the solution in atmospheres? (d) How many grams of lime (CaO) would be needed to neutralize the solution?