General Chemistry

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Which of the following is a triprotic acid? 

<ol style="list-style-type:lower-alpha;">
	<li>NH3</li>
	<li>CH3COOH</li>
	<li>H3PO4</li>
	<li>Al(OH)3</li>
	<li>HNO3</li>
</ol>

 
To identify a triprotic acid from the given list, we need to understand what a triprotic acid is and then analyze each option based on this understanding.

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Definition of a Triprotic Acid

<ul>
	<li>Triprotic Acid: A triprotic acid is an acid that can donate three protons (hydrogen ions, H⁺). This means it has three ionizable hydrogen atoms per molecule.</li>
</ul>

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Analysis of Each Option

<ol style="list-style-type:lower-alpha;">
	<li>NH₃ (Ammonia)

	<ul>
		<li>Ammonia is a base, not an acid. It accepts protons rather than donating them.</li>
		<li>Therefore, NH₃ is not a triprotic acid.</li>
	</ul>
	</li>
</ol>

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<ol style="list-style-type:lower-alpha;">
	<li value="2">CH₃COOH (Acetic Acid)

	<ul>
		<li>Acetic acid is a monoprotic acid, meaning it can donate only one proton.</li>
		<li>The structure of acetic acid has only one ionizable hydrogen atom (the hydrogen in the carboxyl group -COOH).</li>
		<li>Therefore, CH₃COOH is not a triprotic acid.</li>
	</ul>
	</li>
</ol>

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<ol style="list-style-type:lower-alpha;">
	<li value="3">H₃PO₄ (Phosphoric Acid)

	<ul>
		<li>Phosphoric acid has three hydrogen atoms that are ionizable.</li>
		<li>It can donate three protons, one from each of its three hydroxyl groups (-OH).</li>
		<li>Therefore, H₃PO₄ is a triprotic acid.</li>
	</ul>
	</li>
</ol>

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<ol style="list-style-type:lower-alpha;">
	<li value="4">Al(OH)₃ (Aluminum Hydroxide)

	<ul>
		<li>Aluminum hydroxide is not an acid; it&#39;s a base.</li>
		<li>It can accept protons but does not donate them.</li>
		<li>Therefore, Al(OH)₃ is not a triprotic acid.</li>
	</ul>
	</li>
</ol>

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<ol style="list-style-type:lower-alpha;">
	<li value="5">HNO₃ (Nitric Acid)

	<ul>
		<li>Nitric acid is a monoprotic acid, capable of donating only one proton.</li>
		<li>It has only one ionizable hydrogen atom.</li>
		<li>Therefore, HNO₃ is not a triprotic acid.</li>
	</ul>
	</li>
</ol>

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Conclusion

Based on the analysis, the triprotic acid among the given options is c) H₃PO₄ (Phosphoric Acid). It has three ionizable hydrogen atoms and can donate three protons, fitting the definition of a triprotic acid.

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In summary, identifying a triprotic acid involves examining the structure of the acid to determine the number of ionizable hydrogen atoms. Phosphoric acid (H₃PO₄) is the only compound in the given list that meets the criteria of a triprotic acid, with its ability to donate three protons in solution.

Question

Which one of the following is a triprotic acid?

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