Problem 74 - Chemistry: An Atoms-Focused Approach

Question

If \(0.100 M\) aqueous solutions of each of these compounds were prepared, which one would have the lowest pH? (a) \(\mathrm{BaCl}_{2} ;\) (b) \(\mathrm{LiCl} ;\) (c) \(\mathrm{KCl} ;\) (d) \(\mathrm{TiCl}_{4}\)

Step-by-Step Solution

Answer

(a) BaCl₂ (b) LiCl (c) KCl (d) TiCl₄ Answer: (d) TiCl₄

Step 1: Identify acidic/basic behavior of compounds

We first need to identify the acidic or basic behavior of each compound. For this, we look at their chemical formulas and the ions they dissociate into when in solution. (a) BaCl₂ -> Ba²⁺ + 2Cl⁻ This compound dissociates into a barium ion (Ba²⁺) and two chloride ions (Cl⁻). Neither of these ions are acidic or basic, so BaCl₂ is a neutral salt. (b) LiCl -> Li⁺ + Cl⁻ This compound dissociates into a lithium ion (Li⁺) and a chloride ion (Cl⁻). Neither of these ions are acidic or basic, so LiCl is a neutral salt. (c) KCl -> K⁺ + Cl⁻ This compound dissociates into a potassium ion (K⁺) and a chloride ion (Cl⁻). Neither of these ions are acidic or basic, so KCl is a neutral salt. (d) TiCl₄ -> Ti⁴⁺ + 4Cl⁻ This compound dissociates into a titanium ion (Ti⁴⁺) and four chloride ions (Cl⁻). The titanium ion has a strong charge of +4 and can undergo hydrolysis to produce H⁺ ions in solution, making this compound acidic. Ti⁴⁺ + 4H₂O -> Ti(OH)₄ + 4H⁺

Step 2: Comparing the pH of the solutions

Now that we have identified the acidic or basic behavior of each compound, we can compare their pH values. The neutral salts (BaCl₂, LiCl, and KCl) will have a pH of 7, as they do not produce H⁺ or OH⁻ ions in the solution. However, the TiCl₄ compound is acidic and will have a pH lower than 7, as it produces H⁺ ions in the solution through the hydrolysis reaction of Ti⁴⁺ ions.

Step 3: Determining the compound with the lowest pH

Since TiCl₄ is the only compound that produces H⁺ ions in the solution and has a pH lower than 7, it is the compound with the lowest pH among the given options. So the answer is (d) TiCl₄.