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buffers and pH! help!! please ;)


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1. An Acid , HA has a pKa=4.7. Calculate the ratio [A-]/[HA] for the following values:

a) pH=2.7


c)pH=4.7, PH=5.7, pH=6.7 and pH=13.7


2. A buffer at pH 4.5 is made from a weak acid(HA) with pKa of 4.0. What is the ratio of [A]/[HA] in this buffer?

The equilibrium equation for this buffer is HA<--> H+ + A-, Show how this buffer would act to mop up an influx H+ ions.


3. The pH increased from 5.8, the normal pH of a cigarette , to pH 6.4 by addition of ammonia. How many moles of ammonia are required to produce this pH change per cigarette (volume approx. 5ml) ? (Assume that no unprotonated ammonia will exist at pH 6.4)


4. Calculate the pH of normal arterial blood using the information given below:

pKa= 6.1 for CO2 <--> H+ + HCO3-


In arterial blood [HCO3-] =24mM , [CO2]=1.2mM

Suppose the normal arterial blood is suddenly made to accept 11mM of HCl (aq):

a) what is the resulting pH of the blood if no CO2 is allowed to escape?

b)what is the resulting pH of the blood if 11 mM of CO2 can be quickly exhaled by normal processes?

c) under these conditions , a person would actually begin to hyperventilate. how will this help to restore normal pH?

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