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

الأحماض أحادية البروتون كحمض الهيدروفلوريك،تحتوي على بروتون واحد قابل للتأين. وعلى العكس،تحتوي الأحماض متعددة البروتون على اثنين أو أكثر من البروتونات القابلة للتأين. على سبيل المثال،حمض الكبريتوز يحتوي على بروتونين قابلين للتأين،ويحتوي حمض الفوسفوروز على ثلاثة.الحمض متعدد البروتونات يفقد كلًا من بروتوناته تباعًا،ويكون لكل تفاعل قيمة Ka خاصة به. إزالة بروتون من جزيء محايد،أسهل من إزالته من جزيء ذو شحنة سالبة،لأن الشحنة السالبة تزيد من قوة الرابطة بين البروتون وبين الأيون السالب. بالتالي،في حمض الفوسفوريك،تكون قيمة Ka اللازمة لإزالة البروتون الأول Ka1،أعلى منها للبروتون الثاني Ka2،وهي أعلى منها للبروتون الثالث Ka3.يمكن تقدير pH لحمض متعدد البروتون،باستخدام التفاعل الأول،فقط،إذا كانت Ka1 أكبر بألف مرة على الأقل من قيم Ka التي تليها. على سبيل المثال،قيمة pH لمحلول حمض الأسكروبيك تركيزه 0.050 مولار،يمكن تحديدها باستخدام Ka1 وجدول مراقبة تغير ICE. عند إذابته في الماء،يتفكك حمض الأسكروبيك إلى هيدرونيوم وأيونات أسكوربات.قيمة Ka1 لهذا التفاعل هي 8 10⁻⁵،وهي مساوية لتركيز الهيدرونيوم مضروبًا في أيون الأسكوربات الأحادي السالب ويقسم الناتج على تركيز حمض الأسكوربيك. يمكن إعداد جدول مراقبة تغير ICE لهذا التفاعل،بمقارنة قيم التركيز الأولي وقيمه عند التوازن. نظرًا لقيمة x الضئيلة،فإن 0.050 ناقص x تساوي تقريبًا 0.050.باستبدال هذه القيم في معادلة Ka1،تكون قيمة x تساوي 0.0020 مولار،وتشكل 4%فقط من التركيز الأولي لحمض الأسكروبيك. وهكذا يكون التقريب صحيحًا. قيمة pH للمحلول تساوي 2.70.تركيز الأيون السالب الثنائي،الذي تشكل في الخطوة الثانية من التفاعل،يمكن حسابه أيضًا باستخدام Ka2 وجدول مراقبة التغير ICE. حيث Ka2 تساوي 1.6 10-¹²،ويمكن التعبير عنها على أنها،تركيز الهيدرونيوم مضروبًا بتركيز أيون الأسكوربات الثنائي السالب وقسمة الناتج على تركيز أيون الأسكوربات الأحادي السالب. لهذا التفاعل،يُملأ جدول مراقبة التغير ICE بقيمة التركيز الأولي لأيون الأسكوربات الأحادي السالب والهيدرونيوم من التفاعل الأول،وهي 0.002 مولار.نظرًا لقيمة x الضئيلة،يمكن حذفها من التركيز عند التوازن لكل من أيون الأسكوربات الأحادي السالب والهيدرونيوم. بعد استبدال هذه القيم في معادلة Ka2 وحل المعادلة،تكون قيمة x هي 1.6 10-¹² مولار. بما أن x أقل من 5%من 0.002 مولار،يكون التقريب صحيحًا.بما أن تركيز أيونات الهيدرونيوم،التي تكونت أثناء الخطوة الثانية من تفكك حمض الأسكوربيك،ضئيل،فإن البروتون الأول القابل للتأين،هو الذي يحدد pH للمحلول.

أحماض بوليبروتيك

تصنف الأحماض حسب عدد البروتونات لكل جزيء والتي يمكن أن تتخلى عنها في التفاعل. الأحماض مثل HCl و HNO 3 و HCN التي تحتوي على ذرة هيدروجين مؤينة واحدة في كل جزيء تسمى الأحماض الأحادية البروتين. ردود أفعالهم مع الماء هي: <table style = "margin-left: auto؛ margin-right: auto؛"><tbody><tr><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> الأحماض الأحادية: التفاعلات مع الماء </td></tr><tr><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> HCl ( aq ) + H 2 O ( l ) & # 10230 ؛ H 3 O + ( aq ) + Cl & # 8722؛ ( aq ) </td></tr><tr><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> HNO 3 ( aq ) + H 2 O ( l ) & # 10230 ؛ H 3 O + ( aq ) + NO 3 & # 8722؛ ( aq ) </td></tr><tr><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> HCN ( aq ) + H 2 O ( l ) & # 8652 ؛ H 3 O + ( aq ) + CN & # 8722؛ ( aq ) </td></tr></tbody></table> على الرغم من أنه يحتوي على أربع ذرات هيدروجين ، إلا أن حمض الأسيتيك ، CH 3 CO 2 H ، هو أيضًا أحادي النوع لأن ذرة الهيدروجين من مجموعة الكربوكسيل (COOH) تتفاعل مع القواعد: <img alt = "Image1" src = "/ files / ftp_upload / 11405 / 11405_Figure 1.svg" style = "height: 125px؛" /> وبالمثل ، فإن القواعد أحادية الخلية هي قواعد تقبل بروتونًا واحدًا. تحتوي الأحماض ثنائية البروز على ذرتين من الهيدروجين المؤين لكل جزيء ؛ يحدث تأين هذه الأحماض في خطوتين. يحدث التأين الأول دائمًا بدرجة أكبر من التأين الثاني. على سبيل المثال ، يتأين حمض الكبريتيك ، وهو حمض قوي ، على النحو التالي: <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؛"> حمض ثنائي البروتيك: حمض الكبريتيك (H 2 SO4) </قوي> </td></tr><tr><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> 1 st التأين </td><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> H 2 SO 4 ( aq ) + H 2 O ( l ) & # 8652؛ H 3 O + ( aq ) + HSO 4 & # 8722؛ ( aq ) </td><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> K a1 = أكثر من 10 2 ؛ التفكك الكامل </td></tr><tr><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> 2 nd التأين </td><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> HSO 4 & # 8722؛ ( aq ) + H 2 O ( l ) & # 8652؛ H 3 O + ( aq ) + SO 4 2 & # 8722؛ ( aq ) </td><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> K a2 = 1.2 & # 215؛ 10 & # 8722؛ 2 </td></tr></tbody></table> تحدث عملية التأين المتدرجة هذه لجميع الأحماض متعددة البروتينات. حمض الكربونيك ، H 2 CO 3 ، هو مثال على حمض ثنائي البروتيك ضعيف. ينتج عن التأين الأول لحمض الكربونيك أيونات الهيدرونيوم وأيونات البيكربونات بكميات صغيرة. التأين الأول: H 2 CO 3 ( aq ) + H 2 O ( لتر ) & # 8652 ؛ H 3 O + ( aq ) + HCO 3 & # 8722؛ ( aq ) <img alt = "Eq1" src = "/ files / ftp_upload / 11405 / 11405_Equation_1.png" style = "height: 90px؛" /> يمكن أن يعمل أيون البيكربونات أيضًا كحمض. يؤين ويشكل أيونات الهيدرونيوم وأيونات الكربونات بكميات أقل. التأين الثاني: HCO 3 & # 8722؛ ( aq ) + H 2 O ( l ) & # 8652؛ H 3 O + ( aq ) + CO 3 2 & # 8722؛ ( aq ) <img alt = "Eq2" src = "/ files / ftp_upload / 11405 / 11405_Equation_2.png" style = "height: 90px؛" /> K H2CO3 أكبر من K HCO3 & # 8722؛ بمعامل 10 4 ، لذلك H 2 CO 3 هو المنتج المهيمن لأيون الهيدرونيوم في المحلول.هذا يعني أن القليل من HCO 3 & # 8722؛ يتكون من تأين H 2 CO 3 لإعطاء أيونات الهيدرونيوم (وأيونات الكربونات) وتركيزات H 3 O + و HCO 3 & # 8722؛ عمليًا في محلول مائي نقي لـ H 2 CO 3 . 
 إذا كان ثابت التأين الأول لحمض ثنائي البروتين الضعيف أكبر من الثاني بعامل لا يقل عن 20 ، فمن المناسب معالجة التأين الأول بشكل منفصل وحساب التركيزات الناتجة عنه قبل حساب تركيزات الأنواع الناتجة عن التأين اللاحق . تم توضيح هذا النهج في المثال التمرين التالي. تأين حمض ثنائي البروتين & # 8220 ؛ مياه غازية & # 8221 ؛ يحتوي على كمية مستساغة من ثاني أكسيد الكربون المذاب. المحلول حامضي لأن ثاني أكسيد الكربون 2 يتفاعل مع الماء لتكوين حمض الكربونيك H 2 CO 3 . ما هي [H 3 O + ] و [HCO 3 & # 8722؛ ] و [CO 3 2 & # 8722؛ ] في محلول مشبع من CO 2 مع [H 2 CO 3 ] = 0.033؟ <img alt = "Eq3" src = "/ files / ftp_upload / 11405 / 11405_Equation_3.png" style = "height: 90px؛" /> كما تشير ثوابت التأين ، H 2 CO 3 هو حمض أقوى بكثير من HCO 3 & # 8722؛ ، لذلك يمكن معالجة تفاعلات التأين التدريجي بشكل منفصل. باستخدام المعلومات المقدمة ، يتم إعداد جدول ICE لخطوة التأين الأولى هذه: <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؛"> H 2 CO 3 ( aq ) </td><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> H 3 O + ( aq ) </td><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> HCO 3 & # 8722؛ </</tr><tr><td style = "color: black؛ border: 1px Solid black؛ text-align: center؛"> التركيز الأولي (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؛"> تغيير (M) </td><td style = "color: black؛ border: 1px Solid black؛ text-align: center؛"> & # 8722؛ 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؛"> تركيز التوازن (M) </td><td style = "color: black؛ border: 1px Solid black؛ text-align: center؛"> 0.033 & # 8722 ؛ 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> يعطي استبدال تركيزات التوازن في معادلة التوازن <img alt = "Eq4" src = "/ files / ftp_upload / 11405 / 11405_Equation_4.png" style = "height: 90px؛" /> بافتراض x & # 60؛ & # 60؛ 0.033 وحل المعادلة المبسطة ينتج عنه <img alt = "Eq5" src = "/ files / ftp_upload / 11405 / 11405_Equation_5.png" style = "height: 50px؛" /> حدد جدول ICE x على أنه يساوي مولارية أيونات البيكربونات ومولارية أيون الهيدرونيوم: <img alt = "Eq6" src = "/ files / ftp_upload / 11405 / 11405_Equation_6.png" style = "height: 90px؛" /> باستخدام تركيز أيون البيكربونات المحسوب أعلاه ، يخضع التأين الثاني لحساب توازن مماثل: HCO 3 & # 8722؛ ( aq ) + H 2 O ( l ) & # 8652؛ H 3 O + ( aq ) + CO 3 2 & # 8722؛ ( aq ) <img alt = "Eq7" src = "/ files / ftp_upload / 11405 / 11405_Equation_7.png" style = "height: 180px؛" /> للتلخيص: عند التوازن [H 2 CO 3 ] = 0.033 M ؛ [H 3 O + ] = 1.2 & # 215؛ 10 & # 8722؛ 4 ؛ [HCO 3 & # 8722؛ ] = 1.2 & # 215؛ 10 & # 8722؛ 4 م ؛ و [CO 3 2 & # 8722؛ ] = 4.7 & # 160؛ & # 215؛ 10 & # 8722 ؛ 11 M. الحمض الثلاثي هو حمض يحتوي على ثلاث ذرات H قابلة للتأين. حمض الفوسفوريك هو أحد الأمثلة: <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؛"> حمض التريبروتيك: حمض الفوسفوريك (H 3 PO 4 ) </td></tr><tr>
 <td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> 1 st التأين </td><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> H 3 PO 4 ( aq ) + H 2 O ( l ) & # 8652؛ H 3 O + ( aq ) + H 2 PO 4 & # 8722 ؛ ( aq ) & # 160؛ </td><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> K a1 = 7.5 & # 215؛ 10 & # 8722؛ 3 </td></tr><tr><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> 2 nd التأين </td><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> H 2 PO 4 & # 8722؛ ( aq ) + H 2 O ( l ) & # 8652؛ H 3 O + ( aq ) + HPO 4 2 & # 8722؛ ( aq ) </td><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> K a2 = 6.2 & # 215؛ 10 & # 8722؛ 8 </td></tr><tr><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> 3 rd التأين </td><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> HPO 4 2 & # 8722؛ ( aq ) + H 2 O ( l ) & # 8652؛ H 3 O + ( aq ) + PO 4 3 & # 8722؛ ( aq ) </td><td style = "color: black؛ border: 1px solid black؛ text-align: center؛"> K a3 = 4.2 & # 215؛ 10 & # 8722؛ 13 </td></tr></tbody></table> بالنسبة لأمثلة الحمض ثنائي البروز ، فإن كل تفاعل تأين متتالي يكون أقل شمولاً من السابق ، وينعكس في القيم المتناقصة لثوابت التأين الحمضي التدريجي. هذه سمة عامة للأحماض متعددة البروتات وثوابت التأين المتتالية غالبًا ما تختلف بمعامل يبلغ حوالي 10 5 إلى 10 6 . قد تظهر هذه المجموعة من تفاعلات التفكك الثلاثة لإجراء حسابات لتركيزات التوازن في محلول H 3 PO 4 معقدًا. ومع ذلك ، نظرًا لاختلاف ثوابت التأين المتتالية بمعامل 10 5 إلى 10 6 ، توجد اختلافات كبيرة في التغييرات الصغيرة في التركيز المصاحبة لتفاعلات التأين. يسمح هذا باستخدام افتراضات وعمليات تبسيط الرياضيات ، كما هو موضح في الأمثلة أعلاه. القواعد متعددة البروتينات قادرة على قبول أكثر من أيون هيدروجين. أيون الكربونات هو مثال على قاعدة ثنائية البروتونات ، لأنه يمكن أن يقبل بروتونين ، كما هو موضح أدناه. كما هو الحال بالنسبة للأحماض متعددة البروتينات ، لاحظ انخفاض ثوابت التأين مع خطوة التأين. وبالمثل ، فإن حسابات التوازن التي تنطوي على قواعد متعددة البروتينات تتبع نفس الأساليب المتبعة في الأحماض المتعددة البروتينات. <img alt = "Eq8" src = "/ files / ftp_upload / 11405 / 11405_Equation_8.png" style = "height: 90px؛" /> هذا النص مقتبس من<a href="https://openstax.org/books/chemistry-2e/pages/14-5-polyprotic-acids"> Openstax, Chemistry 2e, Section 14.5: Polyprotic Acids</a>.

تصنف الأحماض حسب عدد البروتونات لكل جزيء يمكن أن تتخلى عنها في تفاعل. الأحماض مثل حمض الهيدروكلوريك و HNO3 و HCN التي تحتوي على واحد ...

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Chemistry

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Acids and Bases

الأحماض والقواعد

KEY TERMS AND CONCEPTS

المصطلحات والمفاهيم الأساسية

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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