Experiment_8_-_rev_Jan_03

Experiment_8_-_rev_Jan_03 - 8 H+ Transfer Reactions:...

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Chemistry 1B Experiment 8 29 8 H + Transfer Reactions: Relative Strengths of Acids Introduction In this experiment, you will carry out some proton-transfer reactions. From your observations of each reaction, you will determine which of the two acids is stronger. You will draw conclusions not only by observing the reactions which take place, but also by observing the lack of reaction. The proton-transfer reactions you will attempt are all of the type HA + B HB + A for example, HPO 4 2– + NH 3 NH 4 + + PO 4 3– If you observe that a reaction occurs, you know that K is larger than 1 and G is negative. If the reaction does not happen appreciably, you know that K is less than 1 and G is positive. S is negligibly small for all of these reactions. (“2 pieces 2 pieces”) The relative stability of the reactants and the products ( G) depends mostly on their bond strengths ( H). Looking at the simplified general reaction H–A + B H–B + A you can see that if the reaction goes, then the H–B bond is stronger than the H–A bond; the H + transfers so that it changes from weaker bonding to stronger bonding. If there is no reaction, that means the original H–A bond is stronger than the H–B bond could be, so the H + won’t transfer to the weaker bonding situation. Note that you get the same kind of information (which bond holding H is stronger) whether an attempted reaction goes or not! If you tried to investigate the reaction HF + CN HCN + F
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Chemistry 1B Experiment 8 30 by mixing CN ions with aqueous HF, you would observe the formation of HCN (we will not do this reaction in the laboratory!!). Once you find that HF and CN will react, you know that the equilibrium lies to the right hand side of the reaction as written above. You also know that HCN and F will not react. If you tried to investigate the reaction
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This note was uploaded on 09/04/2011 for the course CHEM 1B taught by Professor Fossum during the Spring '10 term at Laney College.

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Experiment_8_-_rev_Jan_03 - 8 H+ Transfer Reactions:...

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