Chemical Equilibrium - Lecture Notes PDF

‫اﻟﺘﻮازن اﻟﻜﯿﻤﯿﺎﺋﻲ‬ ‫د‪.‬ﻋﻼ ﯾوﻧس‬ ‫د‪.‬ﻋﻼ ﯾوﻧس‬  ‫‪Law of Mass Action‬‬ ‫ ﯾﻧص ﻗﺎﻧون ﻓﻌل اﻟﻛﺗﻠﺔ ل ‪Guldberg and waage‬‬ ‫ﻋﻠﻰ أن ﺳرﻋﺔ اﻟﺗﻔﺎﻋل ﺗﺗﻧﺎﺳب ﺗﻧﺎﺳﺑﺎ طردﯾﺎ ﻣﻊ ﺣﺎﺻل ﺿرب ﺗراﻛﯾز‬ ‫اﻟﻣواد اﻟﻣﺗﻔﺎﻋﻠﺔ ﻛل ﻣرﻓوع...

‫اﻟﺘﻮازن اﻟﻜﯿﻤﯿﺎﺋﻲ‬ ‫د‪.‬ﻋﻼ ﯾوﻧس‬ ‫د‪.‬ﻋﻼ ﯾوﻧس‬  ‫‪Law of Mass Action‬‬ ‫ ﯾﻧص ﻗﺎﻧون ﻓﻌل اﻟﻛﺗﻠﺔ ل ‪Guldberg and waage‬‬ ‫ﻋﻠﻰ أن ﺳرﻋﺔ اﻟﺗﻔﺎﻋل ﺗﺗﻧﺎﺳب ﺗﻧﺎﺳﺑﺎ طردﯾﺎ ﻣﻊ ﺣﺎﺻل ﺿرب ﺗراﻛﯾز‬ ‫اﻟﻣواد اﻟﻣﺗﻔﺎﻋﻠﺔ ﻛل ﻣرﻓوع اﻟﻰ ﻗوة ﺗﺳﺎوي ﻋدد اﻟﻣوﻻت أو اﻷﯾوﻧﺎت‬ ‫اﻟظﺎھرة ﻓﻲ ﻣﻌﺎدﻟﺔ اﻟﺗﻔﺎﻋل‬ ‫‪equilibrium as the condition when the rates of the forward and reverse‬‬ ‫‪reactions are equal‬‬ ‫د‪.‬ﻋﻼ ﯾوﻧس‬  ‫اﻟﻌﻮاﻣﻞ اﻟﻤﺆﺛﺮة ﻋﻠﻰ اﻟﺘﻮازن‬ ‫اﻟﺗرﻛﯾز ‪Concentration‬‬ ‫ ‬ ‫زﯾﺎدة اﻟﺗرﻛﯾز أو ﻧﻘﺻﺎﻧﮫ ﻻﺗُﻐﯾر ﻣن ﻗﯾﻣﺔ ‪k‬وﻟﻛن وﺿﻊ اﻟﺗوازن ﺳوف ﯾﺗﻐﯾر‬ ‫درﺟﺔ اﻟﺣرارة ‪Temperature‬‬ ‫ ‬ ‫درﺟﺔ اﻟﺣرارة ﺗؤﺛر ﻋﻠﻰ ﺳرﻋﺔ اﻟﺗﻔﺎﻋل وﺑﺎﻟﺗﺎﻟﻲ ﺗؤﺛر ﻋﻠﻰ ﻗﯾﻣﺔ ‪k‬‬ ‫ﻣﺛﻼ‪ :‬ﻋﻧدﻣﺎ ﯾﻛون اﻟﺗﻔﺎﻋل اﻟﻣﺑﺎﺷر ﻣﺎص ﻟﻠﺣرارة ‪ endothermic‬ﻣﺎذا ﯾﺣدث ﻓﻲ ﺣﺎل ﻗﻣﻧﺎ ﺑرﻓﻊ درﺟﺔ‬ ‫اﻟﺣرارة؟‬ ‫اﻟﺣواﻓز‪Catalysts‬‬ ‫ ‬ ‫ﻟﮭﺎ ﺗﺄﺛﯾر ﻋﻠﻰ ﺳرﻋﺔ اﻟﺗﻔﺎﻋل وﺑﺎﻟﺗﺎﻟﻲ ﺳرﻋﺔ اﻟوﺻول اﻟﻰ ﺣﺎﻟﺔ اﻟﺗوازن اﻻ‬ ‫أﻧﮭﺎ ﻻﺗؤﺛر ﻋﻠﻰ ﻗﯾﻣﺔ ﺛﺎﺑت اﻟﺗوازن اﻟﻧﮭﺎﺋﯾﺔ )ﻷﻧﮭﺎ ﺗزﯾد ﺳرﻋﺔ اﻟﺗﻔﺎﻋل اﻟﻣﺑﺎﺷر واﻟﻌﻛوس ﺑﻧﻔس اﻟﻣﻌدل*(‬ ‫اﻟﺿﻐط ‪PRESSURE‬‬ ‫ ‬ ‫ﯾؤﺛر ﻋﻠﻰ ﻗﯾﻣﺔ ﺛﺎﺑت اﻟﺗوازن وﻋﻠﻰ وﺿﻌﮫ وﺧﺎﺻﺔ ﻓﻲ ﺗﻔﺎﻋﻼت اﻟﻐﺎزات‬ ‫ﺣﯾث ﯾﺗﺟﮫ اﻟﺗﻔﺎﻋل ﻣﻊ زﯾﺎدة اﻟﺿﻐط اﻟﻰ ﺗﻘﻠﯾل اﻟﺣﺟم‬ ‫د‪.‬ﻋﻼ ﯾوﻧس‬ ‫أﻧﻤﺎط اﻟﺘﻮازن اﻟﻜﯿﻤﯿﺎﺋﻲ‬ ‫د‪.‬ﻋﻼ ﯾوﻧس‬ ‫ ﺗﻧص ھذه اﻟﻘﺎﻋدة ﻋﻠﻰ أﻧﮫ اذا ﺗﻌرض أي ﺗﻔﺎﻋل ﻓﻲ ﺣﺎﻟﺔ ﺗوازن ﻛﯾﻣﯾﺎﺋﻲ اﻟﻰ ﺗﺄﺛﯾر ﺧﺎرﺟﻲ‬ ‫ﻣﺛل ﺗﻐﯾﯾر أﺣد ﺗراﻛﯾزاﻟﻣواد اﻟﻣﺗﻔﺎﻋﻠﺔ أو اﻟﺿﻐط أو درﺟﺔ اﻟﺣرارة ﻓﺈن اﻟﺗﻔﺎﻋل ﺳﯾﺣﺎﻓظ‬ ‫ﻋﻠﻰ ﺗوازﻧﮫ اﻟﺣﻘﯾﻘﻲ وﯾُزﯾل ھذا اﻟﺗﺄﺛﯾروﺗﺑﻘﻰ ‪K‬ﺛﺎﺑﺗﺔ‬ ‫ﻟدﯾك اﻟﺗﻔﺎﻋل اﻟﺗﺎﻟﻲ‪:‬‬ ‫اﺣﺳب ﺛﺎﺑت اﻟﺗوازن ‪K‬‬ ‫د‪.‬ﻋﻼ ﯾوﻧس‬ ‫د‪.‬ﻋﻼ ﯾوﻧس‬ ‫ ﯾﺗﺄﯾن ﺣﻣض اﻟﺧل ﺑﻧﺳﺑﺔ ‪1.73%‬ﻓﺈذا ﻛﺎن ﺗرﻛﯾز اﻟﺣﻣض‬ ‫ﯾﺳﺎوي ‪M 0.058‬اﺣﺳب ﻗﯾﻣﺔ ﺛﺎﺑﺗﺔ اﻟﺗوازن ‪ka‬‬ ‫‪‬‬ ‫د‪.‬ﻋﻼ ﯾوﻧس‬ ‫د‪.‬ﻋﻼ ﯾوﻧس‬  ‫ﻧﻈﺮﯾﺎت اﻟﺤﻤﻮض واﻷﺳﺲ‬ ‫ﻧﻈﺮﯾﺔ أرﯾﻨﯿﻮس ‪Arrhenius theory :‬‬ ‫اﺳﺘﻨﺘﺞ اﻟﻌﺎﻟﻢ أرﯾﻨﯿﻮس ﺳﻨﺔ ‪ 1887‬م ﻧﻈﺮﯾﺔ ﺗﺘﻌﻠﻖ ﺑﺎﻟﻤﺤﺎﻟﯿﻞ اﻹﻟﻜﺘﺮوﻟﯿﺘﯿﺔ واﻟﺘﻲ ﺗﺘﻀﻤﻦ اﻷﺣﻤﺎض واﻷﺳﺲ ‪ ،‬ﺣﯿﺚ ﻋﺮف‬ ‫اﻟﺤﻤﺾ ﻋﻠﻰ أﻧﮫ اﻟﻤﺎدة اﻟﺘﻲ ﻋﻨﺪ ذوﺑﺎﻧﮭﺎ ﻓﻲ اﻟﻤﺎء ﺗﺘﺄﯾﻦ ﺗﻌﻄﻲ ﺷﻮارد اﻟﮭﯿﺪروﺟﯿﻦ اﻟﻤﻮﺟﺒﺔ )‪ ( H+‬واﻷﺳﺎس ھﻲ اﻟﻤﺎدة اﻟﺘﻲ‬ ‫ﺗﻌﻄﻲ ﺷﻮارد اﻟﮭﯿﺪروﻛﺴﯿﺪ اﻟﺴﺎﻟﺒﺔ) ‪. (OH-‬‬ ‫د‪.‬ﻋﻼ ﯾوﻧس‬  ‫‪ -2‬ﻧﻈﺮﯾﺔ ﺑﺮوﻧﺸﺘﻨﺪ – ﻟﻮري ‪Bronsted - Lowry theory‬‬ ‫ﻋﺮﻓﺖ ھﺬه اﻟﻨﻈﺮﯾﺔ اﻟﺤﻤﺾ ﻋﻠﻰ أﻧﮫ اﻟﻤﺎدة اﻟﺘﻰ ﺗﻌﻄﻲ ﺑﺮوﺗﻮﻧﺎ ً ﻓﻰ ﻣﺤﻠﻮﻟﮭﺎ وأن اﻷﺳﺎس ھﻮ اﻟﻤﺎدة اﻟﺘﻰ ﺗﺴﺘﻘﺒﻞ ذﻟﻚ اﻟﺒﺮوﺗﻮن‬ ‫أن ﻟﺒﻌﺾ اﻟﻤﻮاد اﻟﻘﺪرة ﻋﻠﻰ ﻓﻘﺪ واﻛﺘﺴﺎب ﺑﺮوﺗﻮن ﻓﻰ ﻧﻔﺲ اﻟﻮﻗﺖ ﻣﺜﻞ اﻟﻤﺎء وﺗﺴﻤﻲ ﺑﺎﻟﻤﻮاد اﻷﻣﻔﻮﺗﯿﺮﯾﺔ أو اﻟﻤﺬﺑﺬﺑﺔ ‪:‬‬ ‫د‪.‬ﻋﻼ ﯾوﻧس‬ ‫ﻋﻨﺪ ﻣﻘﺎرﻧﺔ ﺛﻮاﺑﺖ اﻟﺘﺸﺮد ﻟﻤﺠﻤﻮﻋﺔ ﻣﻦ اﻷﺣﻤﺎض اﻟﻤﺨﺘﻠﻔﺔ اﻟﺘﻰ ﺗﻢ ﻗﯿﺎﺳﮭﺎ ﻋﻨﺪ ﻧﻔﺲ اﻟﻈﺮوف ﻧﺠﺪ أﻧﮫ ﻛﻠﻤﺎ ﻛﺎﻧﺖ ﻗﯿﻤﺔ‬ ‫‪Ka‬ﻋﺎﻟﯿﺔ ﻛﻠﻤﺎ زادت ﻗﺪرة اﻟﺤﻤﺾ ﻋﻠﻰ اﻟﺘﺄﯾﻦ وﯾﻜﻮن ﺣﻤﻀﺎ ً ﻗﻮﯾﺎ ًوﻧﻔﺲ اﻷﻣﺮ ﻟﻸﺳﺲ اﻟﻀﻌﯿﻔﺔ‪.‬‬ ‫د‪.‬ﻋﻼ ﯾوﻧس‬  ‫‪ -3‬ﻧﻈﺮﯾﺔ ﻟﻮﯾﺲ ‪: Lewis theory‬‬ ‫ﻋﺮﻓﺖ ھﺬه اﻟﻨﻈﺮﯾﺔ اﻟﺤﻤﺾ ﻋﻠﻰ أﻧﮫ ﺗﻠﻚ اﻟﻤﺎدة اﻟﺘﻲ ﻟﮭﺎ اﻟﻤﻘﺪرة ﻋﻠﻰ ﻛﺴﺐ زوج ﻣﻦ اﻹﻟﻜﺘﺮوﻧﺎت وﺗﻌﺘﺒﺮ اﻟﯿﻜﺘﺮوﻓﯿﻼت‬ ‫) ‪ ( electrophile‬وﻋﺮﻓﺖ اﻷﺳﺎس ﻋﻠﻰ أﻧﮭﺎ اﻟﻤﺎدة اﻟﺘﻰ ﻟﮭﺎ اﻟﻤﻘﺪرة ﻋﻠﻰ ﻣﻨﺢ زوج ﻣﻦ اﻹﻟﻜﺘﺮوﻧﺎت وﺗﻌﺘﺒﺮ‬ ‫ﻧﯿﻮﻛﻠﻮﻓﯿﻼت ) ‪: ( nucleophile‬‬ ‫وﺗﺴﻤﻰ اﻟﺮاﺑﻄﺔ اﻟﺘﻰ ﺗﻨﺸﺎ ﻋﻦ طﺮﯾﻖ ﻣﺴﺎھﻤﺔ أﺣﺪى اﻟﺬرات ﺑﺰوج ﻣﻦ اﻹﻟﻜﺘﺮوﻧﺎت ﺑﺎﻟﺮاﺑﻄﺔ اﻟﺘﺴﺎھﻤﯿﺔ اﻟﺘﻨﺎﺳﻘﯿﺔ‬ ‫‪. Coordinate covalent bond‬‬ ‫د‪.‬ﻋﻼ ﯾوﻧس‬  ‫ﺗﻮازن ﺣﻤﺾ أﺳﺎس‬ ‫اﻟﺤﻤﺾ واﻷﺳﺎس اﻟﻘﻮي ﯾﺘﺸﺮد ﺑﺸﻜﻞ ﻛﺎﻣﻞ )ﺗﻔﺎﻋﻞ اﻟﺘﺸﺮد ﻣﺒﺎﺷﺮ(‬ ‫اﻟﺤﻤﺾ واﻷﺳﺎس اﻟﻀﻌﯿﻒ ﯾﺘﺸﺮد ﺑﺸﻜﻞ ﺟﺰﺋﻲ )ﺗﻔﺎﻋﻞ اﻟﺘﺸﺮد‬ ‫ﻋﻜﻮس(‬ ‫د‪.‬ﻋﻼ ﯾوﻧس‬  ‫ﻻﺣظ اﺗﺟﺎه‬ ‫اﻟﺗﻔﺎﻋل‬ ‫ﺣﻣض ﻗوي‬ ‫‪HCl + H2O‬‬ ‫‪H3O+ + Cl-‬‬ ‫ﺣﻣض ﺿﻌﯾف‬ ‫‪HOAC + H2O‬‬ ‫‪H3O+ + OAC-‬‬ ‫] ‪[H 3 O ][OAC‬‬ ‫‪+‬‬ ‫‪−‬‬ ‫= ‪Keq‬‬ ‫]‪[HOAC‬‬ ‫د‪.‬ﻋﻼ ﯾوﻧس‬  ‫ﯾﺘﺸﺮد اﻟﻤﺎء وﻓﻖ اﻟﻤﻌﺎدﻟﺔ‬ ‫‪2H2O‬‬ ‫‪H3O+‬‬ ‫‪+ OH-‬‬ ‫] ‪[ H 3O + ][OH −‬‬ ‫‪Kw‬‬ ‫=‬ ‫‪[ H 2 O ]2‬‬ ‫] ‪[H + ][OH −‬‬ ‫= ‪k‬‬ ‫]‪[H 2 O‬‬ ‫] ‪K w =[ H + ][OH −‬‬ ‫د‪.‬ﻋﻼ ﯾوﻧس‬ - The concentration of water is constant in diluted solutions - Ka and Kw are the molar equilibrium constants At 25°C Kw= 10 -14. at room temperature: ‫وﻣﻧﮫ‬ [H+][OH-]= 10-14 ‫[ ﻓﻲ اﻟوﺳط اﻟﻣﻌﺗدل أواﻟﻣﺎء اﻟﻧﻘﻲ‬H+]=[OH-] = 10-7 ‫ﯾﻛون‬ ‫ ﻋﻼ ﯾوﻧس‬.‫د‬  pH scale pH = - log [H+] A similar definition is made for hydroxyl ion concentration: pOH = - log [OH-] Kw = [H+][OH-] So we can write: pKw= pH + pOH At 25°C 14 = pH + pOH ً ‫ﻣﺗﻰ ﯾﻛون اﻟوﺳط ﺣﻣﺿﯾﺎ‬ ً ‫ﻣﺗﻲ ﯾﻛون أﺳﺎﺳﯾﺎ‬ ‫ﻣﺗﻰ ﯾﻛون ﻣﻌﺗدﻻ‬ ‫ ﻋﻼ ﯾوﻧس‬.‫د‬  ‫ﻟﺤﺴﺎب ‪ pH‬ﯾﻮﺟﺪ ﻟﺪﯾﻨﺎ ﻋﺪة ﺣﺎﻻت‬ ‫ ﺣﻣض ﻗوي‬ ‫ أﺳﺎس ﻗوي‬ ‫ ﺣﻣض ﺿﻌﯾف‬ ‫ أﺳﺎس ﺿﻌﯾف‬ ‫ ﻣﻠﺢ ذو ﺻﻔﺔ أﺳﺎﺳﯾﺔ أو ﺣﻣﺿﯾﺔ‬ ‫ ﻣﺛﺎل ﻋن ﺣﺳﺎب ‪pH‬ﺣﻣض وأﺳﺎس ﻗوي‬ ‫‪Calculate the pH of a 1 × 10-3M solution of HCl‬‬ ‫‪Calculate the pOH and the pH of 2×10-3M solution of NaOH‬‬ ‫د‪.‬ﻋﻼ ﯾوﻧس‬ ‫ اﻟﺣﻣض اﻟﻘوي ﻣﺛل ‪ HCl,HNO3,H2SO4‬وﻛذﻟك اﻷﺳس اﻟﻘوﯾﺔ ﺗﺗﺷرد ﺑﻛل ﻛﺎﻣل أﻣﺎ‬ ‫اﻟﺣﻣوض واﻷﺳس اﻟﺿﻌﯾﻔﺔ ﺗﺗﺷرد ﺑﺷﻛل ﺟزﺋﻲ‬ ‫ ﺣﻣض اﻟﺧل ﺣﻣض ﺿﻌﯾف ﺛﺎﺑﺗﺔ ﺗﺷرد ‪ Ka‬ﻓﻲ درﺟﺔ اﻟﺣرارة ‪25‬‬ ‫] ‪[ H + ][OAc −‬‬ ‫‪= 1.75 × 10 − 5‬‬ ‫]‪[ HOAc‬‬ ‫د‪.‬ﻋﻼ ﯾوﻧس‬  ‫ﻣﺜﺎل ﻋﻦ ﺣﻤﺾ وأﺳﺎس ﺿﻌﯿﻒ‬ -Calculate the pH and pOH of a 10-2M solution of acetic acid ( Ka= 1.75 ×10-5) -Kb for ammonia is 1.75 ×10-5 at 25°C, Calculate the pH and pOH for a 2.00 × 10-3M solution ammonia. ‫ ﻋﻼ ﯾوﻧس‬.‫د‬ ‫ﺣﺎﻟﺔ اﻷﻣﻼح ‪salts of weak acids and weak bases‬‬ ‫ ﯾﺗﺷرد اﻟﻣﻠﺢ ﺑﺷﻛل ﻛﺎﻣل‬ ‫ اﻟﺷﺎردة اﻟﻧﺎﺗﺟﺔ ﻋن ﺗﺷرد اﻟﻣﻠﺢ ﺗﺧﺿﻊ ﻟﺣﻠﻣﮭﺔ )ﺑﺗﻔﺎﻋل ﻋﻛوس(‬ ‫ﻣﺛﺎل‬ ‫د‪.‬ﻋﻼ ﯾوﻧس‬  [𝐶𝐶𝐶𝐶3𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶][𝐎𝐎𝐇𝐇 − ] 𝐊𝐊 𝐇𝐇 = 𝐊𝐊 𝐛𝐛 = [𝐶𝐶𝐶𝐶3𝐶𝐶𝐶𝐶𝐶𝐶−] [𝐶𝐶𝐶𝐶3𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶][𝐎𝐎𝐇𝐇 − ] [𝐇𝐇 + ] 𝐊𝐊 𝐛𝐛 = [𝐶𝐶𝐶𝐶3𝐶𝐶𝐶𝐶𝐶𝐶−] [𝐇𝐇 + ] Kw 1.0 × 10 −14 −10 Kb = = = 5.7 × 10 K a 1.75 × 10 −5 Kw ‫ ﯾﺳﺎوي‬Ka.Kb ‫ أي ﺟداء‬ Kw= KaKb ‫ ﻋﻼ ﯾوﻧس‬.‫د‬  ‫أﻣﺜﻠﺔ‬ Calculate the pH of 0.2 M solution of sodium acetate Calculate the pH of a 0.25 M of ammonium chloride. ‫ﻋﻠﻣﺎ أن‬ Ka acetic acid= 1.75 ×10-5 Kb ammonia= 1.75 ×10-5 ‫ ﻋﻼ ﯾوﻧس‬.‫د‬  Buffer ‫ﻣﺤﻠﻮل اﻟﻮﻗﺎء‬ A buffer solution consists of a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid at predetermined concentrations or ratios ‫ ﻋﻨﺪ إﺿﺎﻓﺔ ﺣﻤﺾ أوأﺳﺎس أوﻋﻨﺪ اﻟﺘﻤﺪﯾﺪ ﺑﺎﻟﻤﺎء‬pH ‫ ﻣﺤﻠﻮل ﯾﻘﺎوم اﻟﺘﻐﯿﺮات ﻓﻲ‬ Henderson- Hasselbalch equation ‫ ﻋﻦ طﺮﯾﻖ ﻣﻌﺎدﻟﺔ‬pH ‫ ﯾﻤﻜﻦ ﺣﺴﺎب‬ [A − ] pH = pK a + log [ HA ] [conjugate base ] pH = pK a + [acid ] [proton acceptor ] pH = pK a + [proton donor ] ‫ ﻋﻼ ﯾوﻧس‬.‫د‬ ‫‪NaHCO3‬‬ ‫د‪.‬ﻋﻼ ﯾوﻧس‬  ‫ﻣﺴﺎﺋﻞ ﻋﻦ اﻟﻮﻗﺎءات‬ Calculate the pH of a buffer prepared by adding 10 ml of 0.1 M acetic acid to 20 ml of o.1M sodium acetate Calculate the pH of a solution prepared by adding 25 ml of 0.1 M sodium hydroxide to 30 ml of 0.20 M acetic acid. ‫ ﻋﻼ ﯾوﻧس‬.‫د‬  Buffer capacity‫ﺳﻌﺔ اﻟﻮﻗﺎء‬ - The buffering capacity is defined as the number of moles of acid or base which are added to 1- liter of buffer solution to cause only 1 unit changing in its pH - The buffering capacity is maximum at pH= pKa ‫ﻛﯾف ﯾﻌﻣل اﻟوﻗﺎء؟‬ ‫ ﻋﻼ ﯾوﻧس‬.‫د‬