Name: stepwise ionization of polyprotic acids
Uploaded: 2020-09-24T15:06:51.000Z
Duration: 3 min 38 s
Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

North Carolina K-12 Science Standard Course of Study

9-12

Physical Science

Matter and its Interactions

PS.PSc.2.5

Polyprotic Acids

חומצות חד-פרוטיות כמו חומצה הידרופלואורית מכילות פרוטון בר יינון אחד. לעומת זאת, חומצות פוליפרוטיות מכילות שני פרוטונים הניתנים ליינון או יותר. לדוגמה, לחומצה גופרתית יש שני פרוטונים הניתנים ליינון, ולחומצה זרחתית יש שלושה.חומצות פוליפרוטיות מאבדות את הפרוטונים זה אחר זה, ולכל תגובה יש את ה-Ka שלה. קל יותר להסיר פרוטון ממולקולה ניטרלית מאשר ממולקולה בעלת מטען שלילי, משום שהמטען השלילי מחזק את הקשר בין הפרוטון לאניון. לכן, בחומצה פוספורית, ה-Ka בעת הסרת הפרוטון הראשון, Ka1, גבוה יותר מבעת הסרת הפרוטון השני, Ka2, שהוא גבוה מ-Ka3.ניתן להעריך את ה-pH של חומצה פוליפרוטית על ידי שימוש בתגובה הראשונה אם Ka1 גדול לפחות פי אלף מה-Ka הבאים. לדוגמה, ה-pH של תמיסת חומצה אסקורבית בריכוז 0.050 מולר ייקבע לפי Ka1 שלו וטבלת ICE. כשחומצה אסקורבית(ויטמין סי)מומסת במים, מתרחש פירוק ליוני הידרוניום ויוני אסקורבט.ה-Ka1 של תגובה זו הוא 8 X כפול 10 בחזקת מינוס 5, והוא שווה לריכוז ההידרוניום כפול ריכוז מונואניון אסקורבי, חלקי ריכוז החומצה האסקורבית. ניתן להכין טבלת ICE לתגובה זו באמצעות הריכוזים ההתחלתיים בשיווי משקל. בגלל הערך הקטן של x, 0.050 פחות x שווה ל-0.050 בקירוב.כאשר מציבים ערכים אלו בביט7וי עבור Ka1, הערך של x שווה ל-0.0020 מולר, שהוא רק 4%מהריכוז ההתחלתי של חומצה אסקורבית. לכן הקירוב תקף. ה-pH של התמיסה שווה 2.70.הריכוז של אסקורבט דואניון שנוצר בשלב השני של התגובה ניתן לחישוב באמצעות Ka2 וטבלת ICE. Ka2 שווה ל-1.6 כפול 10 בחזקת מינוס 12 ויכול להיות מבוטא כריכוז של ההידרוניום כפול הריכוז של אסקורבט דואניון חלקי ריכוז האסקורבט מונואניון. בתגובה זו, טבלת ICE תמולא באמצעות הריכוז ההתחלתי של האסקורבט מונואניון וההידרוניום מהתגובה הראשונה, 0.002 מולר.בשל הערך הקטן של x, ניתן להשמיטו מהריכוזים ההתחלתיים של האסקורבט מונואניון וההידרוניום. אחרי ההצבה של ערכים אלו בביטוי של Ka2 ופתרון, x הוא 1.6 כפול 10 בחזקת מינוס 3 מולר. משום ש-x קטן מ-5%מ-0.002 מולר, הקירוב תקף.בעוד הריכוז של יוני הידרוניום שנוצרו תוך כדי השלב השני של פירוק החומצה האסקורבית זניח, הפרוטון בר היינון הראשון קובע את ה-pH של החומצה.

חומצות פוליפרוטיות

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חומצות מסווגות לפי מספר הפרוטונים למולקולה שהן יכולות לוותר עליהן בתגובה. חומצות כגון HCl,HNO3 ו-HCN המכילות אטום מימן אחד בכל מולקולה נקראות חומצות מונופרוטיות. התגובות שלהם עם מים הן: 
<table style="margin-left: auto; margin-right: auto;"> 
	<tbody> 

		<tr> 

				<td style="color: black; border: 1px solid black; text-align: center;">חומצות מונופרוטיות: תגובות עם מים</td> </tr> 
		<tr> 

				<td style="color: black; border: 1px solid black; text-align: center;">HCl (aq) + H2O (l) ⟶ H3O+ (aq) + Cl− (aq)</td> </tr> 
		<tr> 

				<td style="color: black; border: 1px solid black; text-align: center;">HNO3 (aq) + H2O (l) ⟶ H3O+ (aq) + NO3− (aq)</td> </tr> 
		<tr> 

				<td style="color: black; border: 1px solid black; text-align: center;">HCN (aq) + H2O (l) ⇌ H3O+ (aq) + CN− (aq)</td> </tr> </tbody> </table> 


למרות שהוא מכיל ארבעה אטומי מימן, חומצה אצטית, CH3CO2H, היא גם מונופרוטית מכיוון שרק אטום המימן מקבוצת הקרבוקסיל (COOH) מגיב עם בסיסים: 
<img alt="תמונה 1" src="/files/ftp_upload/11405/11405_Figure 1.svg" style="height: 125px;"> 

באופן דומה, בסיסים מונופרוטיים הם בסיסים שיקבלו פרוטון בודד. 

חומצות דו-פרוטיות מכילות שני אטומי מימן הניתנים ליינון לכל מולקולה; יינון של חומצות כאלה מתרחש בשני שלבים. היינון הראשון תמיד מתרחש במידה רבה יותר מהיינון השני. לדוגמה, חומצה גופרתית, חומצה חזקה, מיוננת באופן הבא: 
<table style="margin-left: auto; margin-right: auto;">
<tbody>
<tr>
<td style="color: black; border: 1px solid black; text-align: center;"></td>
<td colspan="2" style="color: black; border: 1px solid black; text-align: center;">חומצה דו-פרוטית: חומצה גופרתית (H2SO4)</td>
</tr>
<tr>
<td style="color: black; border: 1px solid black; text-align: center;">1st ראשון </td>
<td style="color: black; border: 1px solid black; text-align: center;">H2SO4 (aq) + H2O (l) ⇌H3O+ (aq) + HSO4−(aq)</td>
<td style="color: black; border: 1px solid black; text-align: center;">Ka1 = יותר מ- 102; ניתוק מוחלט</td>
</tr>
<tr>
<td style="color: black; border: 1px solid black; text-align: center;">2nd יינון</td>
<td style="color: black; border: 1px solid black; text-align: center;">HSO4−(aq) + H2O (l) ⇌H3O+ (aq) + SO42−(aq)</td>
<td style="color: black; border: 1px solid black; text-align: center;">Ka2 = 1.2 ×10−2</td>
</tr>
</tbody>
</table>


תהליך יינון צעד זה מתרחש עבור כל החומצות הפוליפרוטיות. חומצה פחמית, H2CO3, היא דוגמה לחומצה דו-פרוטית חלשה. היינון הראשון של חומצה פחמנית מניב יוני הידרוניום ויוני ביקרבונט בכמויות קטנות. 

יינון ראשון: H2CO3 (aq) + H2O (l) ⇌ H3O+ (aq) + HCO3− (aq) 

<img alt="Eq1" src="/files/ftp_upload/11405/11405_Equation_1.png" style="height: 90px;"> 

יון הביקרבונט יכול לשמש גם כחומצה. הוא מיינן ויוצר יוני הידרוניום ויוני קרבונט בכמויות קטנות עוד יותר. 

יינון שני: HCO3− (aq) + H2O (l) ⇌ H3O+ (aq) + CO32− (aq) 
<img alt="Eq2" src="/files/ftp_upload/11405/11405_Equation_2.png" style="height: 90px;"> 

KH2CO3 גדול מ-KHCO3−− בגורם של104, ולכן H2CO3הוא היצרן הדומיננטי של יון הידרוניום בתמיסה. משמעות הדבר היא שמעט מה-HCO3− שנוצר על ידי יינון של H2CO3 מיינן כדי לתת יוני הידרוניום (ויוני קרבונט), והריכוזים של H3O+ ו- HCO3−- כמעט שווים בתמיסה מימית טהורה של H2CO3.

אם קבוע היינון הראשון של חומצה דו-פרוטית חלשה גדול מהשני בגורם של 20 לפחות, ראוי לטפל ביינון הראשון בנפרד ולחשב ריכוזים הנובעים ממנו לפני חישוב ריכוזי מינים הנובעים מהיינון שלאחר מכן. גישה זו מודגמת בתרגיל הבא. 

יינון של חומצה דו-פרוטית 

"מים מוגזים" מכילים כמות מספקת של פחמן דו חמצני מומס. התמיסה חומצית מכיוון ש-CO2 מגיב עם מים ויוצר חומצה פחמנית, H2CO3. מה הם [H3O+], [HCO3−] ו-[CO32−] בתמיסה רוויה של CO2 עם [H2CO3] ראשוני = 0.033?
<img alt="Eq3" src="/files/ftp_upload/11405/11405_Equation_3.png" style="height: 90px;"> 

כפי שמצוין על ידי קבועי היינון, H2CO3 היא חומצה חזקה בהרבה מHCO3-, כך שניתן לטפל בתגובות היינון השלביות בנפרד. בעזרת המידע שסופק, מכינים טבלת ICE עבור שלב היינון הראשון הזה:

<table style="margin-left: auto; margin-right: auto;"> 
	<tbody> 

		<tr> 

				<td style="color: black; border: 1px solid black; text-align: center;"></td> 
				<td style="color: black; border: 1px solid black; text-align: center;">H2CO3 (aq) </td> 
				<td style="color: black; border: 1px solid black; text-align: center;">H3O+ (aq)</td> 
				<td style="color: black; border: 1px solid black; text-align: center;">HCO3− (aq)</td> 
		</tr> 
		<tr> 

				<td style="color: black; border: 1px solid black; text-align: center;">ריכוז התחלתי (M)</td> 
				<td style="color: black; border: 1px solid black; text-align: center;">0.033</td> 
				<td style="color: black; border: 1px solid black; text-align: center;">~0</td> 
				<td style="color: black; border: 1px solid black; text-align: center;">0</td> 
		</tr> 
		<tr> 

				<td style="color: black; border: 1px solid black; text-align: center;">שנה (M)</td> 
				<td style="color: black; border: 1px solid black; text-align: center;">−x</td> 
				<td style="color: black; border: 1px solid black; text-align: center;">+x</td> 
				<td style="color: black; border: 1px solid black; text-align: center;">+x</td> 
		</tr> 
		<tr> 

				<td style="color: black; border: 1px solid black; text-align: center;">ריכוז שיווי משקל(M)</td> 
				<td style="color: black; border: 1px solid black; text-align: center;">0.033 − x</td> 
				<td style="color: black; border: 1px solid black; text-align: center;">x</td> 
				<td style="color: black; border: 1px solid black; text-align: center;">x</td> 
		</tr> 
	</tbody> 
</table> 

החלפת ריכוזי שיווי המשקל במשוואת שיווי המשקל נותנת:
<img alt="Eq4" src="/files/ftp_upload/11405/11405_Equation_4.png" style="height: 90px;"> 

בהנחה של x << 0.033 ופתרון המשוואה הפשוטה מניב:
<img alt="Eq5" src="/files/ftp_upload/11405/11405_Equation_5.png" style="height: 50px;"> 

טבלת ה-ICE הגדירה את x כשווה למולריות יון הביקרבונט ולמולריות יון ההידרוניום: 
<img alt="Eq6" src="/files/ftp_upload/11405/11405_Equation_6.png" style="height: 90px;"> 

באמצעות ריכוז יוני הביקרבונט שחושב לעיל, היינון השני נתון לחישוב בשיווי משקל דומה: HCO3− (aq) + H2O (l) ⇌ H3O+ (aq) + CO32− (aq) 
<img alt="Eq7" src="/files/ftp_upload/11405/11405_Equation_7.png" style="height: 180px;"> 

לסיכום: בשיווי משקל [H2CO3]= 0.033 M; [H3O+] = 1.2 × 10−4;[HCO3−] = 1.2 × 10−4 M; ו[CO32−] = 4.7 × 10−11 M.

חומצה תלת-פרוטית היא חומצה שיש לה שלושה אטומי H הניתנים ליינון. חומצה זרחתית היא דוגמה אחת: 
<table style="margin-left: auto; margin-right: auto;"> 
	<tbody> 

		<tr> 
				<td style="color: black; border: 1px solid black; text-align: center;"></td> 
				<td colspan="2" style="color: black; border: 1px solid black; text-align: center;">חומצה תלת-פרוטית: חומצה זרחתית (H3PO4)</td> 
		</tr> 
		<tr> 
				<td style="color: black; border: 1px solid black; text-align: center;">1st יינון</td> 
				<td style="color: black; border: 1px solid black; text-align: center;">H3PO4 (aq) + H2O (l) ⇌ H3O+ (aq) + H2PO4− (aq)</td> 
				<td style="color: black; border: 1px solid black; text-align: center;">Ka1 = 7.5 × 10−3</td> 
		</tr> 
		<tr> 
				<td style="color: black; border: 1px solid black; text-align: center;">2nd יינון</td> 
				<td style="color: black; border: 1px solid black; text-align: center;">H2PO4− (aq) + H2O (l) ⇌ H3O+ (aq) + HPO42− (aq)</td> 
				<td style="color: black; border: 1px solid black; text-align: center;">Ka2 = 6.2 × 10−8</td> 
		</tr> 
		<tr> 

				<td style="color: black; border: 1px solid black; text-align: center;">3rd יינון</td> 
				<td style="color: black; border: 1px solid black; text-align: center;">HPO42− (aq) + H2O (l) ⇌ H3O+ (aq) + PO43− (aq)</td> 
				<td style="color: black; border: 1px solid black; text-align: center;">Ka3 = 4.2 × 10−13</td> 
		</tr> 
	</tbody> 
</table> 

באשר לדוגמאות של חומצה דו-פרוטית, כל תגובת יינון עוקבת היא פחות נרחבת מהקודמת, המתבטאת בירידה בערכים של קבועי היינון החומצי המדרגתי. זהו מאפיין כללי של חומצות פוליפרוטיות וקבועי יינון עוקבים נבדלים לעתים קרובות בגורם של כ-105 עד 106. 

ייתכן שקבוצה זו של שלוש תגובות דיסוציאציה הופכת את חישובי ריכוזי שיווי המשקל בתמיסה של H3PO4 למסובכת. עם זאת, מכיוון שקבועי היינון העוקבים שונים בגורם של 105 עד 106,, קיימים הבדלים גדולים בשינויים הקטנים בריכוזים הנלווים לתגובות היינון. זה מאפשר שימוש בהנחות ותהליכים מתמטיים-מפשטים, כפי שהודגם בדוגמאות לעיל. בסיסים פוליפרוטיים מסוגלים לקבל יותר מיון מימן אחד. יון הקרבונט הוא דוגמה לבסיס דו-פרוטי, מכיוון שהוא יכול לקבל שני פרוטונים, כפי שמוצג להלן. בדומה למקרה של חומצות פוליפרוטיות, שימו לב שקבועי היינון יורדים עם שלב היינון. כמו כן, חישובי שיווי משקל הכוללים בסיסים פוליפרוטיים פועלים על פי אותן גישות כמו אלה של חומצות פוליפרוטיות.
<img alt="Eq8" src="/files/ftp_upload/11405/11405_Equation_8.png" style="height: 90px;"> 

טקסט זה מותאם מ<a href="https://openstax.org/books/chemistry-2e/pages/14-5-polyprotic-acids"> Openstax, Chemistry 2e, Section 14.5: Polyprotic Acids</a>.</div>

חומצות מסווגות לפי מספר הפרוטונים למולקולה שהן יכולות לוותר עליהן בתגובה. חומצות כגון HCl, HNO3 ו- HCN המכילות ...

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מונחים ומושגים מרכזיים

stepwise ionization of polyprotic acids

Polyprotic acids lose hydrogen ions in steps. The number of ionizable protons in a molecule determines whether an acid is monoprotic, diprotic, or triprotic. This video also shows that polyprotic bases can accept more than one proton.

Monoprotic acids have one ionizable hydrogen atom per molecule. Examples include HCl, HNO3, and HCN. Their reactions with water form hydronium ions and the matching anion. Acetic acid, CH3CO2H, is also monoprotic because only the hydrogen in the carboxyl group reacts with bases. Monoprotic bases accept a single proton.

Diprotic acids have two ionizable hydrogen atoms, so they ionize in two steps. The first ionization is greater than the second. Sulfuric acid is a strong example, with complete first dissociation and a much smaller second dissociation. Carbonic acid, H2CO3, is a weak diprotic acid with the same stepwise pattern. Its first ionization forms hydronium and bicarbonate ions, and its second ionization converts bicarbonate into carbonate in even smaller amounts.

For carbonic acid, the first ionization constant is much larger than the second. In a pure aqueous solution of H2CO3, H3O+ and HCO3− are practically equal, while only a tiny amount of CO3 2− forms. When the first ionization constant is at least 20 times larger than the second, the two steps can be treated separately in equilibrium calculations. The example of saturated CO2 in water uses an ICE table for the first step, then a second equilibrium calculation for bicarbonate.

At equilibrium in that example, [H2CO3] is 0.033 M, [H3O+] is 1.2 × 10−4 M, [HCO3−] is 1.2 × 10−4 M, and [CO3 2−] is 4.7 × 10−11 M. This shows why the first ionization dominates the solution. It also shows how stepwise calculations can simplify polyprotic acid problems.

Triprotic acids have three ionizable hydrogen atoms. Phosphoric acid, H3PO4, is one example. Its three ionization steps produce H2PO4−, then HPO4 2−, and finally PO4 3−. Each successive ionization is less extensive than the one before it. The stepwise acid ionization constants decrease, often by a factor of about 10^5 to 10^6.

That large difference in ionization constants makes equilibrium work easier. Even though a triprotic acid has three dissociation reactions, the small concentration changes can still be handled with simplifying assumptions. Polyprotic bases follow the same idea. The carbonate ion is a diprotic base because it can accept two protons, and its ionization constants also decrease with each step.

Stepwise Ionization of Polyprotic Acids

bronsted-lowry acids and bases

Proton Transfer in Acids and Bases

Acids and bases can be understood through proton transfer. Early scientists described acids by their sour taste, their effect on dyes, and their reaction with limestone, which releases carbon dioxide. Robert Boyle also noted that acid solutions can lose these properties after contact with alkali, or base, solutions. The modern view developed step by step. Humphry Davy showed that hydrogen is the essential part of acids. Joseph Louis Gay-Lussac then described acids as substances that neutralize...

water: a bronsted-lowry acid and base

Water as an Amphiprotic Substance

Water can act as both a Brønsted-Lowry acid and a Brønsted-Lowry base. When hydrogen fluoride dissolves in water, it donates protons to water. This is acid ionization. The products are hydronium ions and fluoride ions. Water can also accept protons from another substance. When pyridine dissolves in water, it accepts a proton from water molecules. This is base ionization. The products are hydroxide ions and pyridinium ions. These reactions show that water can play either role. A substance that...

ph scale

pH and pOH in Water

pH and pOH show how hydronium and hydroxide ions behave in water and other aqueous solutions. These ion concentrations are linked by the ion product of water, K w , so when one goes up, the other goes down. Because ion concentrations can differ by huge amounts, a logarithmic scale is used to describe them. pH is defined from the hydronium ion concentration, [H3O+], and pOH is the matching p-function for hydroxide ion concentration. These two values are also connected through the K w...

relative strengths of conjugate acid-base pairs

relative-strengths-of-conjugate-acid-base-pairs

How Ka and Kb Show Acid-Base Strength

Brønsted-Lowry acid-base chemistry is based on proton transfer. That idea helps show how the strength of an acid is linked to the strength of its conjugate base, and vice versa. Acid and base strength is measured with ionization constants, Ka and Kb, which tell how far an ionization reaction goes. For the conjugate pair HA and A−, the acid ionizes in water and the base reaction can be written for the partner species. When the two reactions are added, they give the autoionization of water. The...

strong acid and base solutions

Strong Acids, Strong Bases, and pH

Strong acids and strong bases change the pH of a solution by dissociating completely in water. A strong acid produces hydronium ions, which are H3O+ ions, and a strong base produces hydroxide ions, OH-. Because the dissociation is complete, the ion concentration can be found from the starting concentration and the molar ratio. For example, 0.20 M hydrobromic acid dissociates fully in water. It produces 0.20 M hydronium ions and 0.20 M bromide ions. A 0.015 M KOH solution also dissociates...

weak acid solutions

Weak Acid Equilibrium in Water

Weak acid equilibrium in water explains why many acids only partially react when dissolved. Most weak acid molecules stay in their original form, and only a small amount of hydronium ions forms. Weak acids are common in nature. They help create the tangy taste of citrus fruits, the stinging sensation from insect bites, and the smells linked to body odor. Acetic acid is a familiar weak acid. It is the main ingredient in vinegar. Its equation uses a double arrow to show that the reaction with...

weak base solutions

Weak Base pH and Kb Calculations

Weak base pH and Kb calculations show how partially reacting bases change water chemistry. Weak bases produce hydroxide ions when they dissolve by reacting with water molecules. Because the reaction only happens partly, these compounds are classified as weak bases. Weak bases are common in nature and in technology. Ammonia is one major example. Global production of ammonia is typically well over 100 metric tons each year. It is used as an agricultural fertilizer, a starting material for...

mixtures of acids

pH of Acid Mixtures

The pH of acid mixtures depends on the acids present, their dissociation constants, and their starting concentrations. When a solution contains two different acids, the pH can be found by choosing the method that fits their relative strengths. This makes acid mixtures a useful case for applying acid-base rules in chemistry. In a mixture of a strong acid and a weak acid, the strong acid dissociates completely and supplies almost all of the hydronium ions in the solution. The weak acid...

ions as acids and bases

Salt Hydrolysis and pH of Solutions

Salt hydrolysis explains why some salt solutions are acidic, basic, or neutral. Salts are ionic compounds made of cations and anions. In water, either ion may react with water through an acid or base ionization reaction. The pH of the solution depends on the relative acid-base strength of the ions in the salt. Ammonium chloride is a good example of an acidic salt. When it dissolves, it separates into ammonium ions and chloride ions. The ammonium ion is the conjugate acid of ammonia, so it can...

determining the ph of salt solutions

Salt Hydrolysis and pH in Solutions

Salt hydrolysis and pH in solutions depend on the ions released when a salt dissolves. Some ions react with water, while others do not. The balance between the cation and anion helps show whether the solution becomes acidic, basic, or neutral. Salts with pH-neutral anions and cations that produce hydronium ions give acidic solutions with pH below 7. Ammonium nitrate is one example. In NH4NO3, NO3− does not react with water, but NH4+ forms hydronium ions, so the solution is acidic. Other salts...

acid/base strengths and dissociation constants

acidbase-strengths-and-dissociation-constants

Acid and Base Strength in Water

Acid and base strength in water depends on how much a substance ionizes after it dissolves. If ionization is nearly complete, the substance is called strong. If only a small amount ionizes, it is called weak. Weak acids and weak bases are much more common than strong ones. The most common strong acids are HClO4, HCl, HBr, HI, HNO3, and H2SO4. The most common strong bases are LiOH, NaOH, KOH, Ca(OH)2, Sr(OH)2, and Ba(OH)2. These strong acids and bases ionize essentially completely in water. <br...

polyprotic acids

Polyprotic acids lose hydrogen ions in steps. The number of ionizable protons in a molecule determines whether an acid is monoprotic, diprotic, or triprotic. This video also shows that polyprotic bases can accept more than one proton. Monoprotic acids have one ionizable hydrogen atom per molecule. Examples include HCl, HNO3, and HCN. Their reactions with water form hydronium ions and the matching anion. Acetic acid, CH3CO2H, is also monoprotic because only the hydrogen in the carboxyl group...

acid strength and molecular structure

How Bonding Affects Acid Strength

Acid strength depends on bonding, electronegativity, and oxidation number. These factors help explain why some hydrogen compounds act as strong acids, while others behave as weak acids or bases. For binary acids, which are hydrogen compounds with one other nonmetal, acidity increases as the H-A bond gets weaker down a group. That is why the order for group 17 is HF &lt; HCl &lt; HBr &lt; HI, and for group 16 it is H2O &lt; H2S &lt; H2Se &lt; H2Te. Across a period, acid strength increases as...

lewis acids and bases

Electron-Pair Reactions in Acid-Base Chemistry

Electron-pair reactions explain Lewis acid-base chemistry. In 1923, G. N. Lewis described acids and bases by how they accept or donate a pair of electrons. When that electron pair forms a coordinate covalent bond, one atom supplies both bonding electrons. This bond is also called a dative bond. A simple example is the reaction of water with a hydrogen ion to make a hydronium ion. Ammonia can also combine with a hydrogen ion to form an ammonium ion. In both cases, the reaction creates a Lewis...

key terms and concepts

Explore how monoprotic, diprotic, and triprotic acids ionize in steps, plus how polyprotic bases accept protons and how to use ICE tables.

Stepwise Ionization of Polyprotic Acids | JoVE K12

chemistry

JoVE Core Chemistry brings general chemistry concepts to life using concise and easy-to-understand animated video lessons. Plus, in the scientist-in-action videos, we demonstrate classical and original research experiments performed in today's laboratories worldwide.

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Ohio’s Learning Standards and Model Curriculum

Interactions Of Matter

Chemical reactions

Minnesota Academic Standards in Science

1.2.1 9L.4.2.2.1

Texas Essential Knowledge and Skills

High School

CHEM.12

CHEM.12.D

Alabama Course of Study Science

Matter and Its Interactions

9-12.PS.3.6.c

Classifying Matter by State

Chemistry is the study of matter and the changes it undergoes. Matter is anything that has mass and occupies space. Matter is all around us; the air, ...

Classifying Matter by Composition

Matter: Pure Substances and Mixtures
According to its composition, the matter can be classified into two broad categories &mdash; pure substances and ...

Elements: Chemical Symbols and Isotopes

A chemical symbol is an abbreviation used to indicate an element or an atom of an element. For example, the symbol for mercury is Hg. The same symbol is ...

Molecules and Compounds

Atoms and Molecules

Everything in the universe is made up of matter, and matter is composed of a combination of elements. An atom is the smallest unit of ...

Solution Formation

There is no one solvent that can dissolve every type of solute. Some substances that readily dissolve in a certain solvent might be insoluble in a ...

Colloids

Children at play often make suspensions such as mixtures of mud and water, flour and water, or a suspension of solid pigments in water known as tempera ...

Construct an explanation to classify matter as a pure substance or mixture; homogeneous or heterogeneous; element or compound; solution, colloid or suspension.

PS.PSc.1.1

Phase Transitions

Whether solid, liquid, or gas, a substance&#39;s state depends on the order and arrangement of its particles (atoms, molecules, or ions). Particles in the ...

phase-transitions-vaporization-and-condensation

Phase Transitions: Vaporization and Condensation

The physical form of a substance changes on changing its temperature. For example, raising the temperature of a liquid causes the liquid to vaporize ...

Vapor Pressure

When a liquid vaporizes in a closed container, gas molecules cannot escape. As these gas phase molecules move randomly about, they will occasionally ...

Clausius-Clapeyron Equation

The equilibrium between a liquid and its vapor depends on the temperature of the system; a rise in temperature causes a corresponding rise in the vapor ...

Phase Transitions: Melting and Freezing

Heating a crystalline solid increases the average energy of its atoms, molecules, or ions, and the solid gets hotter. At some point, the added energy ...

phase-transitions-sublimation-and-deposition

Phase Transitions: Sublimation and Deposition

Some solids can transition directly into the gaseous state, bypassing the liquid state, via a process known as sublimation. At room temperature and ...

Heating and Cooling Curves

When a substance&#8212;isolated from its environment&#8212;is subjected to heat changes, corresponding changes in temperature and phase of the substance ...

Phase Diagrams

A phase diagram combines plots of pressure versus temperature for the liquid-gas, solid-liquid, and solid-gas phase-transition equilibria of a substance. ...

Use models to compare the phases of matter and the physical changes they undergo.

PS.PSc.1.2

physical-and-chemical-properties-of-matter

Physical and Chemical Properties of Matter

The characteristics that enable us to distinguish one substance from another are called properties.

Physical Properties of Matter

A physical property is ...

molecular-comparison-of-gases-liquids-and-solids

Molecular Comparison of Gases, Liquids, and Solids

Particles in a solid are tightly packed together (fixed shape) and often arranged in a regular pattern; in a liquid, they are close together with no ...

Intermolecular vs Intramolecular Forces

Intermolecular forces (IMF) are electrostatic attractions arising from charge-charge interactions between molecules. The strength of the intermolecular ...

Intermolecular Forces

Atoms and molecules interact through bonds (or forces): intramolecular and intermolecular. The forces are electrostatic as they arise from interactions ...

comparing-intermolecular-forces-melting-point-boiling-point

Comparing Intermolecular Forces: Melting Point, Boiling Point, and Miscibility

Intermolecular forces are attractive forces that exist between molecules. They dictate several bulk properties, such as melting points, boiling points, ...

Carry out investigations to compare physical and chemical properties of matter.

PS.PSc.1.3

The Atomic Theory of Matter

The earliest recorded discussion of the basic structure of matter comes from ancient Greek philosophers. Leucippus and Democritus argued that all matter ...

Subatomic Particles

Dalton was only partially correct about the particles that make up matter. All matter is composed of atoms, and atoms are composed of three smaller ...

The Bohr Model

Following the work of Ernest Rutherford and his colleagues in the early twentieth century, the picture of atoms consisting of tiny dense nuclei surrounded ...

Emission Spectra

When solids, liquids, or condensed gases are heated sufficiently, they radiate some of the excess energy as light. Photons produced in this manner have a ...

The de Broglie Wavelength

In the macroscopic world, objects that are large enough to be seen by the naked eye follow the rules of classical physics. A billiard ball moving on a ...

The Uncertainty Principle

Werner Heisenberg considered the limits of how accurately one can measure properties of an electron or other microscopic particles. He determined that ...

Use models to interpret the data presented in Bohr diagrams and electron dot diagrams for neutral atoms of elements 1 through 18.

PS.PSc.1.4

Ions and Ionic Charges

In ordinary chemical reactions, the nucleus &mdash; which contains the protons and neutrons of each atom and thus identifies the element &mdash; remains ...

Use models to compare representations of atoms, ions, and isotopes.

PS.PSc.1.5

The Periodic Table

As early chemists discovered more elements, they realized that various elements could be grouped by their similar chemical behaviors. One such grouping ...

Periodic Classification of the Elements

The periodic table arranges atoms based on increasing atomic number so that elements with the same chemical properties recur periodically. When their ...

atomic-radii-and-effective-nuclear-charge

Atomic Radii and Effective Nuclear Charge

The elements in groups of the periodic table exhibit similar chemical behavior. This similarity occurs because the members of a group have the same number ...

Ionic Radii

Ionic radius is the measure used to describe the size of an ion. A cation always has fewer electrons and the same number of protons as the parent atom; it ...

Ionization Energy

The amount of energy required to remove the most loosely bound electron from a gaseous atom in its ground state is called its first ionization energy ...

Electron Affinity

The electron affinity (EA) is the energy change for adding an electron to a gaseous atom to form an anion (negative ion).



This process can be either ...

Alkali Metals

Group 1 elements are soft and shiny metallic solids. They are malleable, ductile, and good conductors of heat and electricity. The melting points of the ...

Halogens

Group 17 elements, known as halogens, are nonmetals. At room temperature, fluorine and chlorine are gases, bromine is a liquid, and iodine a solid. ...

Noble Gases


The elements in group 18 are noble gases (helium, neon, argon, krypton, xenon, and radon). They earned the name &ldquo;noble&rdquo; because they were ...

Use the Periodic Table as a model to predict the relative properties (metallic/nonmetallic character, ionic charge, and reactivity) and arrangement of elements based on the pattern of valence electrons in the outermost energy levels of atoms.

PS.PSc.1.6

Types of Chemical Bonds

Chemical bonding theories were pioneered by American chemist Gilbert&#xA0;N. Lewis. He developed a model called the Lewis model to explain the type and ...

Ionic Bonding and Electron Transfer

Ions are atoms or molecules bearing an electrical charge. A cation (a positive ion) forms when a neutral atom loses one or more electrons from its valence ...

Covalent Bonding and Lewis Structures

Compared to ionic bonds, which results from the transfer of electrons between metallic and nonmetallic atoms, covalent bonds result from the mutual ...

Bonding in Metals

Metallic bonds are formed between two metal atoms. A simplified model to describe metallic bonding has been developed by Paul Dr&#xFC;de called the ...

Construct an explanation to classify the type of chemical bond that occurs (covalent, ionic, or metallic) in a given substance.

PS.PSc.2.1

Nomenclature of Alkanes

In the late 19th-century, the number of new chemical compounds discovered increased tremendously. Hence, the necessity arose to develop a naming system ...

Nomenclature of Alkenes

The IUPAC naming system for alkenes replaces -an- with -en- in the corresponding parent alkanes. Accordingly, a simple alkene replaces the -ane suffix of ...

Nomenclature of Alkynes

Alkynes are unsaturated hydrocarbons characterized by the presence of carbon-carbon triple bonds and have a general formula CnH2n-2. The nomenclature of ...

structure-and-nomenclature-of-alcohols-and-phenols

Structure and Nomenclature of Alcohols and Phenols

Overview 
Alcohols are one of the most important functional groups in organic chemistry. The name of alcohol comes from the hydrocarbon from which it is ...

Structure and Nomenclature of Ethers

Structure and Bonding
Ethers are organic compounds with an ether functional group which is characterized by an oxygen atom connected to two &#8212; ...

IUPAC Nomenclature of Aldehydes

Aldehydes are named based on the systematic nomenclature rules set by the IUPAC. For acyclic aldehydes, the longest carbon chain containing the aldehydic ...

IUPAC Nomenclature of Ketones

Like aldehydes, ketones are named using IUPAC rules; in this case, by replacing &#8220;e&#8221; in the name of the longest hydrocarbon chain with ...

IUPAC Nomenclature of Carboxylic Acids

IUPAC names of carboxylic acids are systematically derived following a few rules discussed below.
For acyclic saturated monocarboxylic acids, the longest ...

Use models to apply International Union of Pure and Applied Chemistry (IUPAC) conventions to name and write formulas for simple compounds.

PS.PSc.2.2

Understand types, properties, and structure of matter.

Stepwise Ionization of Polyprotic Acids

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