Question

The \(\mathrm{H}^{+}\) ion concentration of a solution is \(1 \mathrm{~mol} \mathrm{~L}^{-1}\). Its \(\mathrm{pH}\) is: (a) \(0.1\) (b) \(1.5\) (c) \(1.0\) (d) 0

Short answer

The pH of the solution is 0.

Step-by-step solution

Understanding the Concept of pH

The pH of a solution is related to the concentration of hydrogen ions (\( \mathrm{H}^{+} \)) in the solution. The pH is calculated using the formula: \[ \mathrm{pH} = -\log_{10}[\mathrm{H}^{+}] \]. This formula helps us find out how acidic or basic a solution is.

Apply the pH Formula

Given the hydrogen ion concentration \( [\mathrm{H}^{+}] \) is \( 1 \mathrm{~mol} \mathrm{~L}^{-1} \), apply the pH formula: \[ \mathrm{pH} = -\log_{10}(1) \].

Calculate the Logarithm

Calculate the logarithm: \( \log_{10}(1) \) is equal to 0, because 10 raised to the power of 0 is 1.

Determine the pH Value

Substitute the value from the logarithm calculation into the formula: \( \mathrm{pH} = -0 \), which equals 0.

Key concepts

Acid-Base Chemistry

Acid-base chemistry is a fascinating branch of chemistry that studies the properties of acids and bases. Acids are substances that increase the concentration of hydrogen ions (\( \mathrm{H}^{+} \)) when dissolved in water, while bases increase the concentration of hydroxide ions (\( \mathrm{OH}^{-} \)). Understanding this concept is crucial for calculating pH, a measure that tells us how acidic or basic a solution is.
Knowing the behavior of acids and bases:

• Acids tend to have a pH less than 7 and a high concentration of hydrogen ions.
• Bases usually have a pH greater than 7 and an excess of hydroxide ions.
• A pH of exactly 7 indicates a neutral solution, like pure water.

To solve problems related to acid-base chemistry, start by determining which component—acid or base—is present and if they are strong or weak. Strong acids and bases dissociate completely in water, which simplifies calculations, as seen in the exercise example where it's assumed that \( [\mathrm{H}^+] = 1 \; \mathrm{mol} \; \mathrm{L}^{-1} \) implies a fully dissociated strong acid.

Logarithmic Scale

The pH scale is a logarithmic scale, which means it displays the hydrogen ion concentration of a solution as a power of ten. This type of scale is incredibly useful for simplifying the huge range of hydrogen ion concentrations into manageable numbers. The formula,\[ \mathrm{pH} = -\log_{10}[\mathrm{H}^{+}] \]transforms these concentrations into numbers typically between 0 and 14.
And here's why a logarithmic scale works so well:

• It compresses a wide range of concentrations into a single, easy number to deal with.
• Each whole number difference on the pH scale represents a tenfold change in \( [\mathrm{H}^+] \).
• It simplifies calculations since the concentration can vary by factors of 10, 100, etc.

This property can sometimes confuse beginners because small changes in pH signify large changes in acidity or basicity. In the exercise, solving for the pH of a \( [\mathrm{H}^{+}] = 1 \; \mathrm{mol} \; \mathrm{L}^{-1} \) solution becomes straightforward: \( \log_{10}(1) \) is 0, simplifying the pH calculation to 0.

Hydrogen Ion Concentration

Hydrogen ion concentration ([\( \mathrm{H}^{+} \)]) is a key player in understanding the acidity of a solution. At its core, it defines the pH value, telling us how many hydrogen ions are present per liter of solution. The higher the \( [\mathrm{H}^{+}] \), the more acidic the solution will be.
Let's break it down:

• A \( [\mathrm{H}^{+}] \) of \( 1 \; \mathrm{mol} \; \mathrm{L}^{-1} \) indicates a very high concentration, typical of a strong acid.
• Lower concentrations, like \( 1 \times 10^{-7} \; \mathrm{mol} \; \mathrm{L}^{-1} \), suggest neutrality (as in pure water).
• Even more diluted hydrogen solutions will act more like bases.

This concentration is critical in calculating the pH using the formula \( \mathrm{pH} = -\log_{10}[\mathrm{H}^{+}] \). When the hydrogen ion concentration is \( 1 \; \mathrm{mol} \; \mathrm{L}^{-1} \), it means the solution is so concentrated that its pH value will be the minimum possible, 0. Always remember that small increases or decreases in \( [\mathrm{H}^{+}] \) can result in significant pH changes.