iPad? 4:37 PM www-awh.aleks.com O STOICHIOMETRY Reaction sequence stoichiometry
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iPad? 4:37 PM www-awh.aleks.com O STOICHIOMETRY Reaction sequence stoichiometry David- Phosphoric acid, a mild acid used among other things as a rust inhibitor, food additive, and etching agent for cavity repair by dentists, can be made from elemental phosphorus in a two step process. In the first step, phosphorus and oxygen react to form diphosphorus pentoxide: ? Pg(s) + 502(g) ? 2P,05(g) alo In the second step, diphosphorus pentoxide and water react to form phosphoric acid (H3PO4 Suppose the yield of the first step is 79.% and the yield of the second step is 73.%. Calculate the mass of phosphorus required to make 7.0 kg of phosphoric acid. Be sure your answer has a unit symbol, if needed, and is rounded to the correct number of significant digits. Explanation Check © 2018 McGraw-Hil Education. All Rights Reserved Terms of Use | PrivacyExplanation / Answer
Second step reaction with molar mass
P2O5 + 3H2O = 2H3PO4
MM: 142 18 98
From the stoichiometry of the reaction
(98*2=) 196 kg H3PO4 produced from = 142 kg P2O5
7 kg H3PO4 produced from = 142*7/196 = 5.071 kg P2O5
% yield = 73%
Actual amount of P2O5 required = theoretical yield / % yield
= 5.071/0.73
= 6.947 kg
First step reaction with molar mass
P4 + 5O2 = 2P2O5
MM: 124 32 142
From the stoichiometry of the reaction
(142*2=) 284 kg P2O5 produced from = 124 kg P4
6.947 kg P2O5 produced from = 124*6.947/284 = 3.033 kg P4
% yield = 79%
Actual amount of P4 required = theoretical yield / % yield
= 3.033/0.79
= 3.8 kg
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