When food enters the stomach, HCl is released and the [H 3 O + ] of the stomach fluid rises to 4 × 10 –2 M. What is the pH of the stomach fluid?

Hey, everyone, we're told that the ch choroid plexus produces the cerebrospinal fluid which contains 5. times 10 to the negative eight molar hydro ions. And hydro is represented by the formula H 30 plus, determine the P H of the cerebrospinal fluid. Now, to answer this question, we need to recall the following formula which is our P H is equivalent to the negative log of the concentration of our hydrogen ions. Now let's go ahead and plug in our value. So we have the negative log of 5.0 times 10 to the negative eight molar. Now when we calculate this out, we end up with a P H of 7.30. So the reason why we have two decimal places for our P H is because we have two significant figures in this concentration. Now, I hope this made sense and let us know if you have any questions.

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10. Acids and Bases

The pH Scale

GOB Chemistry

10. Acids and Bases

The pH Scale

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Problem 64

Textbook Question

When food enters the stomach, HCl is released and the [H₃O⁺] of the stomach fluid rises to 4 × 10^–2 M. What is the pH of the stomach fluid?

Verified step by step guidance

Understand the relationship between [H₃O⁺] and pH. The pH of a solution is calculated using the formula:

pH = - \log ({[H}_{3} O])

. This formula tells us that pH is the negative logarithm (base 10) of the hydronium ion concentration.

Identify the given value for [H₃O⁺]. From the problem, the hydronium ion concentration is

4 \times 10^{- 2}

Substitute the given [H₃O⁺] value into the pH formula. This gives:

pH = - \log (4 \times 10^{- 2})

Break the calculation into two parts for clarity. First, use the logarithmic property:

\log (4 \times 10^{- 2}) = \log (4) + \log (10^{- 2})

. Then, recall that

\log (10^{- 2}) = - 2

Combine the results. The pH is calculated as:

pH = - (\log (4) + - 2)

. Simplify further to find the final pH value.

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Key Concepts

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

pH Scale

The pH scale measures the acidity or basicity of a solution, ranging from 0 to 14. A pH of 7 is neutral, while values below 7 indicate acidity and above 7 indicate alkalinity. The scale is logarithmic, meaning each whole number change represents a tenfold change in hydrogen ion concentration.

Hydronium Ion Concentration

Hydronium ion concentration, represented as [H₃O⁺], indicates the amount of hydronium ions present in a solution. It is directly related to the acidity of the solution; higher concentrations correspond to lower pH values. In this case, a concentration of 4 x 10⁻² M indicates a significant level of acidity.

Calculating pH

To calculate pH, the formula pH = -log[H₃O⁺] is used, where [H₃O⁺] is the concentration of hydronium ions in moles per liter. This calculation allows us to determine the acidity of the solution quantitatively. For example, if [H₃O⁺] is 4 x 10⁻² M, the pH can be calculated to find the exact acidity level.

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