Question

Compute \(\left[\mathrm{H}^{+}\right]\) for a solution for which \(\mathrm{pH}=5.8\)

Short answer

The concentration of hydrogen ions \(\left[\mathrm{H}^{+}\right]\) in the solution, when the pH is 5.8, is approximately \(1.58 \times 10^{-6}\) M.

Step-by-step solution

Understand the given information and requirements

The task is to compute the hydrogen ion concentration (\(\left[\mathrm{H}^{+}\right]\)) for a solution where the pH is 5.8. We need to employ the mathematical relationship between the concentration of hydrogen ions and pH, which is given by the formula \(\left[\mathrm{H}^{+}\right] = 10^{-\text{pH}}\). This formula is derived from the definition of pH, which is the negative base-10 logarithm of the molar concentration of hydrogen ions in the solution.

Substitute the given pH value into the formula

To calculate the concentration of hydrogen ions, substitute the given pH value of 5.8 into the formula to obtain \(\left[\mathrm{H}^{+}\right] = 10^{-5.8}\).

Compute the hydrogen ion concentration

Finally, calculate the hydrogen ion concentration \(\left[\mathrm{H}^{+}\right]\) by raising 10 to the power of -5.8. This gives us \(\left[\mathrm{H}^{+}\right] \approx 1.58 \times 10^{-6}\) M, where 'M' indicates molar concentration.

Key concepts

Hydrogen Ion Concentration

When scientists and educators talk about hydrogen ion concentration, they are focusing on the amount of hydrogen ions, represented by \( [\mathrm{H}^+] \), in a solution. This concentration is crucial because it determines a solution's acidity or basicity. Acidic solutions have higher concentrations of hydrogen ions, while basic solutions have fewer.

The scale used to measure this is the pH scale, which runs from 0 to 14. A pH of 7 is considered neutral, a pH less than 7 is acidic, and a pH greater than 7 is basic. The concentration of hydrogen ions can be very small, hence it's convenient to use the scale where a small change in pH represents a large change in \( [\mathrm{H}^+] \). Understanding the connection between pH value and \( [\mathrm{H}^+] \) not only helps in solving chemistry problems but also provides vital information regarding the chemical characteristics of a solution.

Logarithmic Functions

In mathematics, logarithmic functions are the inverses of exponential functions. They can be a bit tricky to comprehend at first, but they're very useful in various scientific fields, including chemistry. The pH calculation is a perfect example of the application of logarithms.

The pH scale itself is logarithmic, meaning each whole number increase or decrease on the pH scale represents a tenfold increase or decrease in hydrogen ion concentration. Therefore, a solution with a pH of 5 has ten times more \( [\mathrm{H}^+] \) than a solution with a pH of 6. This is due to the base-10 logarithm used in the pH formula \(\text{pH} = -\log_{10} [\mathrm{H}^+]\). Logarithmic functions are instrumental in converting between the pH scale and the actual concentration of hydrogen ions, allowing for easier calculation and understanding of the solutions' properties.

Molar Concentration

Molar concentration, often denoted by the symbol 'M' for molarity, measures the amount of a substance in a liter of solution. It is expressed in moles per liter (mol/L), where one mole corresponds to Avogadro's number of particles, approximately \(6.022 \times 10^{23}\) molecules or ions.

In the context of our pH problem, molar concentration tells us how many moles of hydrogen ions are present in one liter of solution. It is a fundamental concept in chemistry that quantifies the strength of an acidic or basic solution. For a clear understanding, if a solution has a high molar concentration of hydrogen ions, it is strong and acidic. Conversely, if the concentration is low, the solution is weakly acidic or may even be basic. This concept is crucial when calculating pH, as seen in the exercise, where we determine the concentration of hydrogen ions to understand the solution's nature.