# General Chemistry Faculty of Allied Medical Sciences (MGGC-101)

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General Chemistry Faculty of Allied Medical Sciences (MGGC-101)

Supervision: Prof.Dr.Shehata El-Sewedy Dr.Fatma Ahmed Limiting reagent, theoretical and percent yield

Outcomes By the end of this lecture, the students will be able to 1-Understand the Limiting Reagent 2-learn to excess reactant of the reactions 3-To differentiate between theoretical and percentage yield 4-Recognize actual yield

Limiting Reagent The limiting reagent (or limiting reactant): is the reactant which is completely consumed in the reaction. The other reactant will be in excess. For example

Limiting Reagents 3.9 2NO + 2O 2 2NO 2 NO is the limiting reagent O 2 is the excess reagent

Example Zinc metal reacts with hydrochloric acid by the following reaction: Zn(s) + 2 HCl(aq)  ZnCl 2 (aq) + H 2 (g) If 0.30 mol Zn is added to hydrochloric acid containing 0.52 mol HCl, how many moles of H 2 are produced? Answer : Take each reactant and calculate how much product would be obtained if each were totally consumed. The reactant that gives the smaller amount is the limiting reagent. Zn  H 2 1 mole I mole 0.30 mole X ?  X (no of moles of H 2 ) = 0.30 mole. similarly: 2 HCl  H 2 2 mole I mole 0.52 mole X ?  X (no of moles of H 2 ) = 0.26 mole. Since HCl is the limiting reagent, the amount of H 2 produced must be 0.26 mol. Zinc is the excess reactant.

Example 2SO 2 (g) + O 2 (g) + 2H 2 O( l ) → 2H 2 SO 4 (aq) How much H 2 SO 4 can be formed from 5 moles of SO 2 and 2 moles O 2 and unlimited quantity of H 2 O ? Answer SO 2 : 2H 2 SO 4 2:2 5X mol 5 moles of SO 2 will give 5 moles of H 2 SO 4, while O 2 : H 2 SO 4 1 :2 2X H 2 SO 4 formed = 4 moles 2 moles O 2 will give 4 moles of H 2 SO 4.  O 2 is the limiting reagent

Theoretical and Percent Yield The theoretical yield of product is the maximum amount of product that can be obtained from given amounts of reactants. The percentage yield is the actual yield (experimentally determined) expressed as a percentage of the theoretical yield (calculated).

Example 2C 6 H 12 + 5O 2  2H 2 C 6 H 8 O 4 + 2H 2 O cyclohexane adipic acid Assume that the reaction start with 25gram cyclohexane which is the limiting reagent. a-What is the theoretical yield of adipic acid. b- If you obtain 33.5gram adipic acid calculate the % yield. Answer 2C 6 H 12  2H 2 C 6 H 8 O 4 2moles : 2 moles 2(mol. mass) 2(mol.mass) 2X 84 2X 146 25g X g Grams adipic acid= 2  146X25/2X84 = 43.45 grams. a- Theortical yield = 43.45gram. b- % yield = (33.5 / 43.45)  100 = 77.1%

Quiz time

Zinc metal reacts with hydrochloric acid by the following reaction: Zn(s) + 2 HCl(aq)  ZnCl 2 (aq) + H 2 (g) If 0.30 mol Zn is added to hydrochloric acid containing 0.52 mol HCl, how many moles of H 2 are produced? 2SO 2 (g) + O 2 (g) + 2H 2 O( l ) → 2H 2 SO 4 (aq) How much H 2 SO 4 can be formed from 5 moles of SO 2 and 2 moles O 2 and unlimited quantity of H 2 O ? 2C 6 H 12 + 5O 2  2H 2 C 6 H 8 O 4 + 2H 2 O cyclohexane adipic acid Assume that the reaction start with 25gram cyclohexane which is the limiting reagent. a-What is the theoretical yield of adipic acid. b- If you obtain 33.5gram adipic acid calculate the % yield.

Student Question

Define Limiting Reagent Theoretical yield Percentage yield 2C 6 H 12 + 5O 2  2H 2 C 6 H 8 O 4 + 2H 2 O cyclohexane adipic acid Assume that the reaction start with 25gram cyclohexane which is the limiting reagent. a-What is the theoretical yield of adipic acid. b- If you obtain 33.5gram adipic acid calculate the % yield.

Assignments(2) Group A and Group B Hend Nazmy – Heba Waheed – Hagar Eman Gamal - Adel Addition reaction Mostafa Ahmad Shata – Abd El Rahman Ali-Mohamad Magdi- Motasem Abd El-Aal Combination reaction Mohamad Mahmoud Awad-Marwa Ahmad-Sara Emad –Mariam Hamdy Application of nitric acid Marina Maged-Nourhan Emad-Engy Roshdy-Madonna Micheal-JosianIsaq- Merna Farag Allah-Christin Magdi- Verona Romani-Makarious Maher- Mena Malak Theoretical yield

Assignments(3) Group A and Group B Eman Gamal- Mona Ashraf Kamal- Fahd Abd El Salam-Mohamad Montaser-Wasal Mohamad Solution Kholod El-Said – Riham Hassan – Esraa Hafez-Asmaa Basha –Asmaa Mohamad Hassan-Dina Nassem Chemical equilibrium Ibrahim Abd El Aatti-John Micheal- Bishoy Sadeek Application of Hydrochloric acid Mariam Thrwat- Kyrillos Rafaat – Mina Kabeel-Fadi Abd El Salam Uses of Helium Khaled Eid- Sameh Raafat- Bishoy Shanoda-Sobhy Sabry-Ahmad Saeed Shehata-Abd El Rahman Abd El Aziz- Ahmad Zian-Mohamad Waheed Gases

A SSIGNMENTS (4) Group A and Group B Someya Mostafa – Maram Ahmad – Esraa Mahmoud Poisonous Inorganic substances Youssef AboBakr – Mina Melad – Omar Gamal Kamal Uses of Noble gases

R ECOMMENDED TEXTBOOKS : 1-Raymond Chang. Chemistry. 10th ed. 2009 2-Zumdehl. International edition. 2009