During exercise when the body lacks an adequate supply of oxygen to support ener

Question

During exercise when the body lacks an adequate supply of oxygen to support energy production, the vate that is produced from the breakdown of glucose is converted into lactate. High lactate levels can ead to acidity in the muscle cells as some of the lactate hydrolyzes to lactic acid. The dissociation of lactic acid to lactate is shown in the reaction below. Lactic acid has a pk, of 3.86. OH Lactic Acid Lactate A solution containing a mixture of lactic acid and lactate was found to have a pH of 3.12. Calculate the ratio of the lactate concentration to the lactic acid concentration in this solution. Number [lactate lactic acid]-L846 What fraction of the lactic acid/lactate mixture is lactic acid? Number fraction lactic acid= 0.156

Explanation / Answer

A buffer is any type of substance that will resist pH change when H+ or OH- is added.

This is typically achieved with equilibrium equations. Both type of buffer will resist both type of additions.

When a weak acid and its conjugate base are added, they will form a buffer

The equations:

The Weak acid equilibrium:

HA(aq) <-> H+(aq) + A-(aq)

Weak acid = HA(aq)

Conjugate base = A-(aq)

Neutralization of H+ ions:

A-(aq) + H+(aq) <-> HA(aq); in this case, HA is formed, H+ is neutralized as well as A-, the conjugate

Neutralization of OH- ions:

HA(aq) + OH-(aq) <-> H2O(l) + A-(aq) ; in this case; A- is formed, OH- is neutralized as well as HA.

Now,

The buffer equation is given by

p H= pKa + log(lactate/lactic acid)

substitute data given, pKa and pH

3.12 = 3.86 + log(lactate/lactic acid)

(lactate/lactic acid) = 10^(3.12-3.86) = 0.18197

apply fractional

for 1 mol of lactic acid

lactate = 0.18197*1 = 0.18197

total = 0.18197+1 = 1.18197

lactic acid fractional = 0.18197 / 1.18197 = 0.1539

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