Stoichiometric Equations & Problems

311: Industrial Chemistry

INTRODUCTION Industrial Chemistry deals with the preparation of products from raw materials through the agency of chemical change. Chemistry is important to industry by:  Regulating manufacturing process  Quality Control  Research & Development Sources of Raw Materials from the natural environment    

Lithosphere – Earth’s Crust Hydrosphere – Marine and Oceanic Environment Atmosphere – Air Plants – Flora

Classification of Natural Resources 1. Renewable Resources that generate themselves Forestry, fishery, and wildlife 2. Non-Renewable Resources that are formed over long periods of time Minerals, metals, and organic materials  Renewable resources can be non renewable when the rate of consumption of renewable resources is greater than the rate of regeneration Chemical Industries commonly manufactured:  Heavy Chemicals o Common acids, soda ash, salt  Fine Chemicals o Result from a series of small-scale chemical operations Characteristics of Chemical Industry  It must be essentially science-based industry  It must be with great commitment and investment to Research & Development Eight Standard Industrial Classifications 1. 2. 3. 4. 5.

Industrial Inorganic Chemicals Plastic Materials, and Synthetics Drugs Soap, Cleaners, and Toilet Goods Paints and Allied Products Prepared by: Benedict S. Marzan

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311: Industrial Chemistry

6. Industrial Organic Chemicals 7. Agricultural Chemicals 8. Miscellaneous Chemical Products Typical Structure of a Chemical Manufacturing Process Raw Materials

Chemical Reactions

Physical Treatment

Separation & Purification

Raw Materials

Unreacted Materials

Primary Types of Chemical Reactions 1. Batch Reactions -Chemicals are added to the reactor at the same time and products are emptied completely when the reaction is finished 2. Continuous Reactions -Reactants are added and products are removed at a constant rate from the reactor

General Principles of Industrial Chemistry - When undertaking a case study of a particular chemical industry, the following characteristics must be studied: 1. Feedstock (Raw materials, preparation) 2. Rate(Temperature and Pressure Variables) 3. Production Yield 4. Co-Products/By-Products 5. Waste Disposal and Effluent Control 6. Quality Control 7. Safety 8. Costs 9. Site Location 10. Suitable Materials for the Construction of a Chemical Plant

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311: Industrial Chemistry

Stoichiometric Relations Moles of excess reactant required Moles of reactant ∈excess Excess Reactant = react withlimitingreactant ¿ × 100 ¿

Excess Reactant =

Excess reactant supplied−Theoretical excess reactan t ×10 0 Theoretical excess reactant

Conversion=

Amount of reactant reacted × 10 0 Amoumt of reactant introduced

Completion=

Amount of limiting reactant reacted ×10 0 Amount of Limiting reactant introduced

%Yeild=

ActualYield Product × 10 0 Theoretical Yield Product

Moles of desi ¿ Selectivity=¿ product formed Moles of undesired product formed

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311: Industrial Chemistry

Problems for Stoichiometry 1. The most important commercial process for converting N 2 from the air into nitrogen-containing compounds is based if the reaction of N 2 and H2 to form ammonia (NH3). a) How many moles of NH3 can be formed from .1071 gram of N2 and 3 grams of H2? b) Which is the Limiting Reactant? c) Which is the Excess Reactant? 2. A strip of zinc metal with a mass of 2.00 g is placed in an aqueous solution containing 2.50g of silver nitrate, causing the following reaction to occur: Zn (s) + 2 AgNO3 (aq) a) b) c) d)

2 Ag (s) + Zn(NO 3)2 (aq)

Which is the limiting reactant? How many grams of Ag will form? How many grams of Zn(NO3)2 will form? How many grams of excess reactant will be left at the end of the reaction?

3. Adipic Acid, H2C6H8O4, is used to produce nylon. The acid is made commercially by a controlled reaction between cyclohexane (C6H12) and O2: 2 C6H12 (l) + 5 O2 (g)

2 H2C6H8O4 (l) + 2 H2O (g)

a) Assume that you carry out this reaction starting with 25.0 g of cyclohexane and that cyclohexane is the limiting reactant. What is the theoretical yield of adipic acid? b) If you obtain 33.5 g of adipic acid from your reaction, what is the percentage yield of adipic acid? 4. In a small scale reaction, the process by which iron ore containing Fe 2O3 is converted into iron by the equation: Fe2O3 (s) + 3 CO (g)

2 Fe (s) + 3 CO 2 (g)

a) If you start with 150 g of Fe2O3 as the limiting reagent, what is the theoretical yield of Fe? b) If the actual yield of Fe in your test was 87.9 g, what was the percentage yield? 5. Antimony is obtained by heating pulverized stibnite (Sb 2S3) with scrap iron and drawing off the molten antimony from the bottom of the reaction vessel: Sb2S3 + Fe

Sb + FeS

Suppose that 0.600 kg of stibnite and 0.250 kg of iron turnings are heated together to give 0.200 kg of Sb metal. Calculate the following: a) Limiting Reactant Prepared by: Benedict S. Marzan

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311: Industrial Chemistry b) c) d) e)

Percent Excess Reactant Degree of Completion % Conversion of Sb2S3 to Sb Yield of Sb

Problems for Gas Laws 1. A sample of 100 grams of an ideal gas at 0.8 bar pressure has its volume doubled and absolute temperature tripled. Find the final pressure. 2. Calcium Carbonate, CaCO3(s), decomposes upon heating to give CaO(s) and CO2(g). A sample of CaCO3 is decomposed, and the carbon dioxide is collected in a 250-ml flask. After the decomposition is complete, the gas has a pressure of 1.3 atm at a temperature of 31 oC. How many moles of CO2 gas were generated? 3. Find the molar volume of an ideal gas at 23oC and 1atm. 4. What is the density of N2 at 80oC and 745 mmHg compared to air at 80oC and 745 mmHg? 5. A certain mixture of N2 and O2 has a density of 1.185g/L at 101.325kPa. Find the mole fraction of O2 in the mixture. 6. A gaseous mixture made from 6.00g O2 and 9.00g CH4 is placed in a 15.0L vessel at 0oC. What is the partial pressure of each gas, and what is the total pressure in the vessel? 7. A study of the effects of certain gas on plant growth requires a synthetic atmosphere composed of 1.5 mol percent CO 2, 18.0 mol percent O2, and 80.5 mol percent Ar. a. Calculate the partial pressure of O2 in the mixture if the total pressure of the atmosphere is to be 745 torr. b. If this atmosphere is to be held in a 121-L space at 295K, how many moles of O2 are needed? 8. A sample of KClO3 is partially decomposed, producing O2 gas that is collected over water. The volume of gas collected is 0.250-L at 26 oC and 765 torr total pressure. Prepared by: Benedict S. Marzan

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311: Industrial Chemistry

a. How many moles of O2 are collected? b. How many grams of KClO3 were decomposed?

Prepared by: Benedict S. Marzan

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