$HNO_2$ Ionizes According To The Reaction: $\[ HNO_2 \leftrightarrow H^+ + NO_2^- \\]If The \[H^+\] Of A 0.20 M Solution Of $HNO_2$ Is 0.010 M, What Is The $K_a$?

Determination of Acid Dissociation Constant ($K_a$) of Nitrous Acid ($HNO_2$)

Nitrous acid ($HNO_2$) is a weak acid that ionizes in aqueous solutions to produce hydrogen ions ($H^+$) and nitrite ions ($NO_2^-$). The acid dissociation constant ($K_a$) is a measure of the strength of an acid, which is defined as the ratio of the concentrations of the products to the reactants in the ionization reaction. In this article, we will determine the $K_a$ of nitrous acid using the given concentrations of $H^+$ and $HNO_2$.

The ionization reaction of nitrous acid is given by:

${ HNO_2 \leftrightarrow H^+ + NO_2^- }$

This reaction indicates that one molecule of nitrous acid dissociates into one hydrogen ion and one nitrite ion.

We are given the concentrations of $H^+$ and $HNO_2$ as 0.010 M and 0.20 M, respectively.

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The acid dissociation constant ($K_a$) is defined as:

${ K_a = \frac{[H^+][NO_2^-]}{[HNO_2]} }$

Since the reaction is at equilibrium, the concentrations of the products are equal to the concentrations of the reactants. Therefore, we can substitute the given concentrations into the equation:

${ K_a = \frac{(0.010)(0.20)}{0.20} }$

Simplifying the equation, we get:

${ K_a = 0.010 }$

The $K_a$ value of 0.010 indicates that nitrous acid is a weak acid, which means that it does not completely dissociate in aqueous solutions. The $K_a$ value is a measure of the strength of an acid, with higher values indicating stronger acids.

In conclusion, we have determined the $K_a$ of nitrous acid using the given concentrations of $H^+$ and $HNO_2$. The $K_a$ value of 0.010 indicates that nitrous acid is a weak acid.

One limitation of this experiment is that the concentrations of $H^+$ and $HNO_2$ may not be accurate due to experimental errors. Additionally, the $K_a$ value may not be constant at different temperatures or concentrations.

Future directions for this experiment include:

• Measuring the $K_a$ value at different temperatures to determine its temperature dependence.
• Measuring the $K_a$ value at different concentrations to determine its concentration dependence.
• Comparing the $K_a$ values of different acids to determine their relative strengths.

• Atkins, P. W., & De Paula, J. (2010). Physical chemistry (9th ed.). Oxford University Press.
• Chang, R. (2010). Physical chemistry for the biosciences. University Science Books.

The following is a list of the equations used in this article:

• Ionization reaction: $HNO_2 \leftrightarrow H^+ + NO_2^-$
• Acid dissociation constant: $K_a = \frac{[H^+][NO_2^-]}{[HNO_2]}$

Note: The appendix is not included in the final article.
Frequently Asked Questions (FAQs) about Acid Dissociation Constant ($K_a$) of Nitrous Acid ($HNO_2$)

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A: The acid dissociation constant ($K_a$) is a measure of the strength of an acid, which is defined as the ratio of the concentrations of the products to the reactants in the ionization reaction.

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A: The $K_a$ value is calculated using the equation:

${ K_a = \frac{[H^+][NO_2^-]}{[HNO_2]} }$

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A: The $K_a$ value of nitrous acid ($HNO_2$) is 0.010.

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A: Nitrous acid ($HNO_2$) is a weak acid, which means that it does not completely dissociate in aqueous solutions.

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A: The $K_a$ value is a measure of the strength of an acid, with higher values indicating stronger acids.

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A: Yes, the $K_a$ value can be affected by temperature or concentration. It is essential to measure the $K_a$ value under controlled conditions to obtain accurate results.

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A: The $K_a$ value can be measured using various methods, including titration, spectrophotometry, and chromatography.

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A: The $K_a$ value has various applications in chemistry, including:

• Determining the strength of acids and bases
• Predicting the pH of solutions
• Understanding chemical reactions and equilibria
• Developing new chemical processes and products

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A: Yes, the $K_a$ value can be used to predict the behavior of other acids. By comparing the $K_a$ values of different acids, chemists can determine their relative strengths and predict their behavior in various chemical reactions.

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A: Some limitations of the $K_a$ value include:

• Experimental errors and uncertainties
• Temperature and concentration dependence
• Limited applicability to complex systems

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A: The $K_a$ value has various real-world applications, including:

• Developing new chemical processes and products
• Improving the efficiency of chemical reactions
• Understanding and predicting the behavior of complex systems
• Developing new materials and technologies

In conclusion, the acid dissociation constant ($K_a$) is a fundamental concept in chemistry that plays a crucial role in understanding the behavior of acids and bases. By understanding the $K_a$ value, chemists can predict the behavior of acids and bases, develop new chemical processes and products, and improve the efficiency of chemical reactions.