A current of 11.3 A is applied to 1.25 L of a solution of 0.552 M HBr converting some of the H⁺ to H₂(g), which bubles out of solution. What is the pH of the solution after 73 minutes?

Name: Chemistry: A Molecular Approach
Author: Tro
ISBN: 9780134112831

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Determine the initial moles of HBr in the solution using the formula: \( \text{moles} = \text{molarity} \times \text{volume} \).

Calculate the total charge passed through the solution using the formula: \( Q = I \times t \), where \( I \) is the current in amperes and \( t \) is the time in seconds.

Use Faraday's laws of electrolysis to find the moles of \( H^+ \) converted to \( H_2 \) gas. The number of moles of electrons is equal to \( \frac{Q}{F} \), where \( F \) is Faraday's constant (96485 C/mol).

Subtract the moles of \( H^+ \) converted to \( H_2 \) from the initial moles of \( H^+ \) to find the remaining moles of \( H^+ \) in the solution.

Calculate the new concentration of \( H^+ \) ions and use the formula \( \text{pH} = -\log[H^+] \) to find the pH of the solution.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Electrolysis

Electrolysis is a chemical process that uses an electric current to drive a non-spontaneous reaction. In this context, the current applied to the HBr solution causes the reduction of H+ ions to form hydrogen gas (H2), which escapes as bubbles. Understanding electrolysis is crucial for determining how much H+ is converted and how it affects the solution's pH.

Molarity and Stoichiometry

Molarity (M) is a measure of concentration defined as moles of solute per liter of solution. In this problem, the initial concentration of HBr is 0.552 M, which helps calculate the number of moles of H+ present. Stoichiometry allows us to relate the amount of H+ converted to H2 gas during electrolysis, which is essential for determining the change in pH.

pH Calculation

pH is a logarithmic scale used to specify the acidity or basicity of a solution, calculated as pH = -log[H+]. As H+ ions are converted to H2 gas, the concentration of H+ decreases, leading to an increase in pH. Understanding how to calculate pH based on changes in H+ concentration is vital for solving the problem.

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A metal forms the fluoride MF₃. Electrolysis of the molten fluo- ride by a current of 3.86 A for 16.2 minutes deposits 1.25 g of the metal. Calculate the molar mass of the metal.

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Textbook Question

A sample of impure tin of mass 0.535 g is dissolved in strong acid to give a solution of Sn²⁺. The solution is then titrated with a 0.0448 M solution of NO₃^–, which is reduced to NO(g). The equivalence point is reached upon the addition of 0.0344 L of the NO₃^– solution. Find the percent by mass of tin in the original sample, assuming that it contains no other reducing agents.

To what pH should you adjust a standard hydrogen electrode to get an electrode potential of -0.122 V? (Assume that the partial pressure of hydrogen gas remains at 1 atm.)

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A current of 11.3 A is applied to 1.25 L of a solution of 0.552 M HBr converting some of the H+ to H2(g), which bubles out of solution. What is the pH of the solution after 73 minutes?

Key Concepts

Electrolysis

Molarity and Stoichiometry

pH Calculation

A current of 11.3 A is applied to 1.25 L of a solution of 0.552 M HBr converting some of the H⁺ to H₂(g), which bubles out of solution. What is the pH of the solution after 73 minutes?