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 to1-Understand the Limiting Reagent

2-learn to excess reactant of the reactions3-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 + 2O2 2NO2

NO is the limiting reagent

O2 is the excess reagent

Example Zinc metal reacts with hydrochloric acid by the following reaction:Zn(s) + 2 HCl(aq) ZnCl2(aq) + H2(g)If 0.30 mol Zn is added to hydrochloric acid containing 0.52 mol HCl, how many moles of H2 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

H2

1 mole I mole

0.30 mole X ?

X (no of moles of H2) = 0.30 mole.

similarly:2 HCl H2

2 mole I mole

0.52 mole X ?

X (no of moles of H2) = 0.26 mole.Since HCl is the limiting reagent, the amount of H2 produced must be 0.26 mol. Zinc is the excess reactant.

Example 2SO2(g) + O2(g) + 2H2O(l) → 2H2SO4(aq) How much H2SO4 can be formed from 5 moles of SO2 and 2 moles O2 and unlimited quantity of H2O ?

Answer SO2 : 2H2SO4

2 : 25 X mol

5 moles of SO2 will give 5 moles of H2SO4, while O2 : H2SO4

1 : 22 X

H2SO4 formed = 4 moles2 moles O2 will give 4 moles of H2SO4 . O2 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).

%100yield ltheoretica

yield actual Yield%

Example 2C6H12 + 5O2 2H2C6H8O4 + 2H2O 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 2C6H12 2H2C6H8O4

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) ZnCl2(aq) + H2(g)If 0.30 mol Zn is added to hydrochloric acid containing 0.52 mol HCl, how many moles of H2 are produced?

2SO2(g) + O2(g) + 2H2O(l) → 2H2SO4(aq) How much H2SO4 can be formed from 5 moles of SO2 and 2 moles O2 and unlimited quantity of H2O ?

2C6H12 + 5O2 2H2C6H8O4 + 2H2O 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

2C6H12 + 5O2 2H2C6H8O4 + 2H2O 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(1)Group A and Group B

Hanan Ahmad Zaid -Alfa Magdi - Alaa Kamal Anani – Asmaa Mohamad El-Awadi- Sara Ali Abd El-Latif- Alaa Emad El Din – Eisha Youssef

Nitrous acid

Hagar Saeed – Shrouk Abd El-Aziz – Mona Ashraf Ramadan – Nahed Atia –Mai Mahmoud-Haidy Mahmoud – Walaa Ebada

NMR spectroscopy

Eman Gamal- Mona Ashraf Kamal- Fahd Abd El Salam-Mohamad Montaser-Wasal Mohamad

Uses of Gases in industry

Asmaa Gamal-Mahmoud Ezzat-Shady Ahmad-Taha Mohamad Nasri - Eisha Ali

Mass spectroscopy

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

ASSIGNMENTS(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

RECOMMENDED TEXTBOOKS:

1-Raymond Chang. Chemistry. 10th ed. 20092-Zumdehl. International edition. 2009