AcidBaseandBufferProblems

AcidBaseandBufferProblems - After taking the smallest...

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Cut to the Chase: Acid, Base, and Buffer Problems When working Acid, base, and buffer problems, approach it as if there are only two types of problems. PROBLEM TYPE I means there will be no X in the problem. It is a limiting reactant problem. It is easy to tell if the reaction is the type . If either of the reactants is a strong acid or a strong base, then the reaction is of the type. ( Really stress whether to use or  in the reaction. The type of arrow tells how to work the problem.) Examples: If you react 0.1 mole of HCl with 0.05 mole of NH 3 ( In one liter): R H + + NH 3 NH 4 + I 0.1 0.05 0 C -0.05 -0.05 + 0.05 ( the smallest amount will always go to 0) E 0.005 0 0.005
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Unformatted text preview: After taking the smallest amount to zero, if H + or OH-is left over, just take the log and get the pH. PROBLEM TYPE II Double arrows means an equilibrium problem and Xs will be in the rice chart. Example: 0.1 mole of HF and 0.5 mole of NaF are mixed to make one liter. R HF + H 2 O H 3 O + + F-I 0.1 0 0.5 ( ignore the water because it will not be in the K expression) C -X X X E 0.1 - X X 0.5 + X Now substitute the E column into the equilibrium expression and solve for X. Since the Ka for HF is so small ( 7.2 X 10-4 ) the X compared to 0.1 and 0.5 may be ignored so the quadratic equation does not have to be used....
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