H2po4 Ka

H2PO4- Ka: Understanding the Acid Dissociation Constant of Dihydrogen Phosphate

Introduction:

Dihydrogen phosphate, H₂PO₄⁻, is an ion crucial in various biological and chemical processes. Understanding its acid dissociation constant (Ka) is essential for predicting its behavior in solutions and its role in buffering systems. This article will delve into the significance of H₂PO₄⁻'s Ka, exploring its calculation, implications, and applications through a question-and-answer format.

1. What is the Acid Dissociation Constant (Ka) and why is it important for H₂PO₄⁻?

The acid dissociation constant (Ka) quantifies the strength of an acid in solution. It represents the equilibrium constant for the dissociation of an acid into its conjugate base and a proton (H⁺). For H₂PO₄⁻, the dissociation reaction is:

H₂PO₄⁻ (aq) ⇌ H⁺ (aq) + HPO₄²⁻ (aq)

The Ka expression is:

Ka = [H⁺][HPO₄²⁻] / [H₂PO₄⁻]

The Ka value for H₂PO₄⁻ is approximately 6.2 x 10⁻⁸ at 25°C. A smaller Ka value indicates a weaker acid. This value is critical because it dictates the pH of solutions containing H₂PO₄⁻ and determines its effectiveness in buffering systems. It allows us to predict the relative concentrations of H₂PO₄⁻, H⁺, and HPO₄²⁻ at equilibrium, which is crucial for understanding its role in biological systems and chemical processes.

2. How is the Ka value of H₂PO₄⁻ determined experimentally?

The Ka value can be experimentally determined through various techniques, primarily involving pH measurements. One common method involves titrating a solution of a dihydrogen phosphate salt (e.g., NaH₂PO₄) with a strong base (e.g., NaOH). By monitoring the pH change during the titration and using the Henderson-Hasselbalch equation, we can calculate the Ka value. Alternatively, sophisticated techniques like potentiometry or spectrophotometry can also be employed to measure the concentrations of the different species at equilibrium and subsequently calculate Ka. Precise measurements are critical as even small variations in temperature can significantly affect the Ka value.

3. What is the significance of the H₂PO₄⁻/HPO₄²⁻ buffer system?

The H₂PO₄⁻/HPO₄²⁻ buffer system is a crucial biological buffer, playing a vital role in maintaining the pH of intracellular and extracellular fluids. Its pKa (the negative logarithm of Ka) of approximately 7.2 is close to the physiological pH of 7.4, making it highly effective in resisting pH changes. This buffering action is critical because drastic pH fluctuations can disrupt enzymatic activity and other cellular processes. The kidneys actively regulate the ratio of H₂PO₄⁻ to HPO₄²⁻ in the blood to maintain a stable pH. For example, if the blood becomes too acidic, the kidneys excrete more H⁺ ions and retain more HPO₄²⁻, shifting the equilibrium to consume the excess H⁺.

4. What are some real-world applications of understanding H₂PO₄⁻'s Ka?

Understanding the Ka of H₂PO₄⁻ has diverse applications:

Agriculture: Phosphate fertilizers often contain dihydrogen phosphate salts. Knowing the Ka helps determine the optimal pH for soil application, maximizing nutrient uptake by plants.
Food Industry: H₂PO₄⁻ acts as a buffer and acidity regulator in various food products. Controlling pH is crucial for maintaining food quality, texture, and preventing spoilage.
Pharmaceuticals: Many pharmaceutical formulations utilize phosphate buffers to maintain the stability and effectiveness of drugs.
Chemical Analysis: Ka is used in various analytical techniques, such as potentiometric titrations, to determine the concentration of phosphate ions in solutions.

5. How does temperature affect the Ka value of H₂PO₄⁻?

Like most equilibrium constants, the Ka value of H₂PO₄⁻ is temperature-dependent. Generally, increasing the temperature increases the Ka value, indicating a slightly stronger acid at higher temperatures. This is because the dissociation reaction is endothermic, meaning it absorbs heat. According to Le Chatelier's principle, increasing the temperature shifts the equilibrium towards the products (H⁺ and HPO₄²⁻), resulting in a higher Ka value. However, the change is relatively small within the typical physiological temperature range.

Conclusion:

Understanding the acid dissociation constant (Ka) of dihydrogen phosphate (H₂PO₄⁻) is essential for numerous applications across various fields. Its role in biological buffering systems, its impact on agricultural practices, and its importance in the food and pharmaceutical industries highlight its significance. The Ka value provides valuable information for predicting the behavior of H₂PO₄⁻ in different environments and helps in controlling and optimizing various processes.

FAQs:

1. How does the Ka of H₂PO₄⁻ relate to its pKa? The pKa is simply the negative logarithm of the Ka: pKa = -log₁₀(Ka). Using pKa simplifies calculations and comparisons of acid strengths.

2. Can H₂PO₄⁻ undergo further dissociation? Yes, HPO₄²⁻, the conjugate base of H₂PO₄⁻, can further dissociate to form PO₄³⁻ and H⁺. This dissociation also has its own Ka value, which is much smaller than the Ka of H₂PO₄⁻.

3. How does the presence of other ions affect the Ka of H₂PO₄⁻? The presence of other ions, especially those that can interact with H⁺ or HPO₄²⁻, can influence the apparent Ka value through ionic strength effects. These effects are often addressed using activity coefficients in more rigorous calculations.

4. What are some common salts of dihydrogen phosphate? Monosodium dihydrogen phosphate (NaH₂PO₄) and potassium dihydrogen phosphate (KH₂PO₄) are common examples used in various applications.

5. How can I calculate the pH of a solution containing a known concentration of NaH₂PO₄? Use the Ka expression and an ICE table (Initial, Change, Equilibrium) to determine the equilibrium concentrations of H⁺, H₂PO₄⁻, and HPO₄²⁻, and then calculate the pH using the equation: pH = -log₁₀[H⁺]. Approximations can be made if the Ka value is significantly smaller than the initial concentration of NaH₂PO₄.

Search Results:

Solved How is the Ka for H2PO4 - determined from the pKa - Chegg (1) The Ka is determined by p K a is as follows:-The relationship between p K a and K a and

Q18.12P Question: Write the Ka expressio... [FREE SOLUTION] To write the K a expression of H 2 PO 4 - in water, we should write the balanced reaction first –. H 2 PO 4 - (aq) +H 2 O (l) ⇌ H 3 O + (aq) + HPO 4 2 - (aq) Then write the K a expression using the formula below. Note that it only includes aqueous species. K a = [product] [reactant] K a = [H 3 O +] [HPO 4 2 -] [H 2 PO 4 -]

What is the Pka for potassium phosphate? - Socratic 6 Jan 2016 · What is the Pka for potassium phosphate? H 3P O4 +H 2O → H 2P O− 4 + H 3O+ Ka1 = 7.25 ×10−3. H 2P O− 4 + H 2O → H P O2− 4 + H 3O+ Ka2 = 6.31 ×10−8. H P O2− 4 +H 2O → P O3− 4 +H 3O+ Ka3 = 4.8 × 10−13. I assume the one you want is for potassium dihydrogen phosphate, K+ −OP (= O)(OH)2, i.e. H 2P O2− 4. pKa2 = 7.20.

Acid and Base Chart — Table of Acids & Bases - MilliporeSigma Read these instructions to learn how to use this acids and bases chart. The table lists the K a values and the strength of each acid and base. Acids with a K a value less than one are considered weak and get weaker as we move to the bottom of the table.

Table of Acid and Base Strength - UW Departments Web Server 1. Strong acids are listed at the top left hand corner of the table and have Ka values >1 2. Acid with values less than one are considered weak. 3. The strong bases are listed at the bottom right of the table and get weaker as we move to the top of the table.

Acid Ka Values - ScienceGeek.net Note: A K a of "very large" indicates a strong acid.

Amphoteric Compounds: Ka of H2PO4 & HS Reaction Explained 16 Nov 2011 · The Ka of H2PO4 is 6.3 * 10^-8. The Ka of HS is 1.3 * 10^-13. Write a formula for the reaction of these substances and explain your results. Both are amphoteric. The formula is: H2PO4 + HS <--> HPO4 + H2S. I figured that the H2PO4 will act more like the acid in this particular situation because it has a higher value of Ka.

The Ka for H2PO4- is 6.3 x 10-8. The Ka for HS- is 1.3 x 10-13. The value of Ka for phenol (a weak acid) is 1.00 x 10-10. What is the value of Kb for its conjugate base, C6H5O-? Write equations that show H_2PO_4 acting both as an acid and as a base.

The Ka for the H2PO4/HPO4 buffer is given by the equation: … 11 Jan 2025 · Solution For The Ka for the H2PO4/HPO4 buffer is given by the equation: [HPO4 ]/ [H2PO4 ] = 10^ 7.20. What is the pH of a 1:2 mixture of H2PO4 to HPO4 (See the table for the activity coeff.

1. What is the Ka expression for HPO.? - Brainly.com 25 Aug 2023 · The Ka expression for HPO, presumably derived from H3PO4 losing two protons, is represented by the second stage of phosphoric acid dissociation and is Ka2 = [HPO42-][H+] / [H2PO4-]. It describes equilibrium concentrations of the reactants and products.

Solved 1. Write the acid dissociation expression (ka) for - Chegg Question: 1. Write the acid dissociation expression (ka) for the following reaction below: (5 points) a) HPO 2(aq) + H2O(l) <---> H30+ (aq) + PO43- (aq) b) Write the conjugate base of H2PO4, give a brief explanation of how you found the conjugate base below to receive credit: (5 points) 2.

What is Ka for H3PO4 (aq) H (aq) H2PO4- (aq)? - Answers 3 Jun 2024 · The equilibrium constant expression for the dissociation of H3PO4 is: H3PO4(aq) ⇌ H+(aq) + H2PO4-(aq) K_a = [H+][H2PO4-] / [H3PO4] The value of Ka for this reaction is …

Ka Table (Chang) - Grosse Pointe Public Schools pH = - log[H+] [H+] = 10-pH pOH = -log[OH-] [OH-] = 10-pOH pH + pOH = 14 K w = 10-14 = K a ·K b pK a = -log K a K a = 10-pKa K a Table (Chang) (Acid) (Base) Ka ...

Ka Table - University of Rhode Island Acid Ionization Constants at 25 °C. Acid Formula K a. Acetic acid HC 2 H 3 O 2 1.8×10 –5 Acrylic acid HC 3 H 3 O 2 5.5×10 –5 Aluminum 3+ ion Al 3+ (aq) 1.4×10 –5 Ammonium ion NH 4 + 5.6×10 –10 Anilinium ion C 6 H 5 NH 3 + 1.4×10 –5 Arsenic acid H 3 AsO 4 6.0×10 –3 H 2 AsO 4 – 1.0×10 –7. HAsO 4 2– 3.2×10 –12. Arsenous acid H 3 AsO 3 6.6×10 –10 Ascorbic acid H 2 C ...

1.3: Acid Strength (Ka) - Chemistry LibreTexts 31 Dec 2024 · To know the relationship between acid or base strength and the magnitude of Ka, Kb, pKa, and pKb. To understand the leveling effect. The magnitude of the equilibrium constant for an ionization reaction can be used to determine the relative strengths of acids and bases.

Why Does 0.10 M Dihydrogen Phosphate Dissociate Rather than … 23 Dec 2018 · It seems as though Ka does play a role in determining whether an amphoretic substance will act like a base or acid, since 0.10 M Hydrogen Phosphate has a Ka of 4.8x10^-13 and creates a basic solution.

STRONG AND WEAK ACIDS - chemguide Explains the meaning of the terms strong and weak as applied to acids, and introduces pH, Ka and pKa

Dihydrogen phosphate - Wikipedia Dihydrogen phosphate is an inorganic ion with the formula [H 2 PO 4] −. Phosphates occur widely in natural systems. [1] These sodium phosphates are artificially used in food processing and packaging as emulsifying agents, neutralizing agents, surface-activating agents, and leavening agents providing humans with benefits.

Shown in Table 1 are the Ka values for phosphoric | Chegg.com Shown in Table 1 are the Ka values for phosphoric acid (there are three acidic hydrogens), and for carbonic acid (there are two acidic hydrogens). (A) Write out the reaction of HPO4 2− with water to produce PO4 3− and one other product.

Table of Acids with Ka and pKa Values* CLAS - Gelman Library Conjugate acids (cations) of strong bases are ineffective bases. * Compiled from Appendix 5 Chem 1A, B, C Lab Manual and Zumdahl 6th Ed. The pKa values for organic acids can be found in Appendix II of Bruice 5th Ed. * Compiled from Appendix 5 Chem 1A, B, C Lab Manual and Zumdahl 6th Ed.

H2po4 Ka

H2PO4- Ka: Understanding the Acid Dissociation Constant of Dihydrogen Phosphate

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