Chemical Engineering Calculations Reviewer

Embed Size (px)

Citation preview

SAMPLE PROBLEMS: Material Balances in Reactive/Non-Reactive SystemsTaken From: Sinnott, R.K., CHEMICAL ENGINEERING DESIGN, Volume 6, Fifth Edition, 2005, by Elsevier Butterworth-Heinemann

______ 1. Two thousand kilograms of five percent slurry of calcium hydroxide in water is to be prepared by diluting twenty percent slurry. The percentages are by weight. How much 20% slurry do you need?a. 500 kgb. 1500 kgc. 1750 kgd. none of these

For nos. 2 to 4-______ 2. Consider the production of a nitration acid by mixing 70% nitric and 98% sulfuric acid. How much is the number of distinct chemical species in this process?a. 2b. 3c. 4d. 5

For numbers 3 and 4

______ 3. If nitration acid is made up using oleum in place of the 98% sulfuric acid, how many distinct chemical species are there?a. 2b. 3c. 4d. 5

______ 4. If nitration acid is made up using oleum in place of the 98% sulfuric acid, how many independent components/species are there?a. 2b. 3c. 4d. 5

______ 5. The feed stream to a reactor contains ethylene = 16%, oxygen = 9%, nitrogen = 31%, and hydrogen chloride. If the ethylene flow is 5000 kg/hr, calculate the total stream flow. All percentages are by weight.a. 31250 kg/hrb. 2813 kg/hrc. 9687 kg/hrd. 13750 kg/hr

______ 6. Carbon dioxide is added at a rate of 10 kg/hr to an air stream and the air is sampled at a sufficient distance downstream to ensure complete mixing. If the analysis shows 0.45% v/v CO2, calculate the air-flow rate in kg/hr.a. 1560 b. 6075c. 2240d. none of these

______ 7. In a test on a furnace fired with natural gas (composition 95% methane, 5% nitrogen), the following flue gas analysis was obtained: carbon dioxide 9.1%, carbon monoxide 0.2%, oxygen 4.6%, nitrogen 86.1%, all percentages by volume. Calculate the percentage excess air flow (percentage above stoichiometric).a. 15%b. 22%c. 34%d. none of these

______ 8. To ensure complete combustion, 20% excess air is supplied to a furnace burning natural gas. The gas composition (by volume) is methane 95%, ethane 5%. Calculate the moles of air required per mole of fuel.a. 207.5 molesb. 11.86 molesc. 1.2 molesd. none of these

_______ 9. In the manufacture of vinyl chloride (C2H4Cl2) by the pyrolysis of dichloroethane (DCE), the reactor conversion is limited to 55% to reduce carbon formation, which fouls the reactor tubes. Calculate the quantity of DCE fed to the reactor to produce 5000 kg/h of VC.a. 80 kmol/hrb. 145.5 kmol/hrc. 44 kmol/hrd. none of these

_______ 10. In the production of ethanol by the hydrolysis of ethylene, diethyl ether is produced as a byproduct. A typical feed stream composition is 55% ethylene, 5% inerts, 40% water; and product stream: 52.26% ethylene, 5.49% ethanol, 0.16% ether, 36.81% water, 5.28% inerts. Calculate the selectivity of ethylene for ethanol.

a. 94.4%b. 5.44%c. 10%d. 9.45%

_______ 11. In the chlorination of ethylene to produce dichloroethane (DCE), the conversion of ethylene is reported as 99.0%. If 94 mol of DCE are produced per 100 mol of ethylene reacted, calculate the overall yield based on ethylene. The unreacted ethylene is not recovered.

a. 94%b. 93.1%c. 66.7%d. 49.33%

_______ 12. In the production of ammonia from hydrogen and nitrogen, the conversion, based on either raw material, is limited to 15%. The ammonia produced is condensed from the reactor (converter) product stream, and the unreacted material is recycled. If the feed contains 0.2% argon (from the nitrogen separation process), calculate the purge rate (mole purge/mole feed) required to hold the argon in the recycle stream below 5.0%. Percentages are by volume.

a. 4 b. 5c. 8d. none of these

Answers:1. 2. A3. B4. C (sulfuric acid, sulfur trioxide, nitric acid, water.)5. B (The sulfur trioxide will react with the water producing sulfuric acid, so there are only three independent components.)6. D7. A8. B9. B10. B11. A12. B13. A