A microbiologist is preparing a medium on which to culture

e. coli bacteria. she buffers the medium at ph 7.00 to minimize the effect of acid-producing fermentation. what volumes of equimolar aqueous solutions of k2hpo4 and kh2po4 must she combine to make 800.0 ml of the ph 7.00 buffer

Question

Chemistry

Hood

16 January, 23:48

A microbiologist is preparing a medium on which to culture

e. coli bacteria. she buffers the medium at ph 7.00 to minimize the effect of acid-producing fermentation. what volumes of equimolar aqueous solutions of k2hpo4 and kh2po4 must she combine to make 800.0 ml of the ph 7.00 buffer

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Ruth Fischer · Answer 1

H3PO4 pKa2 = 7.21

H2PO4 - (aq) - - > HPO4-2 (aq) + H + (aq) Ka2

pH = pKa + log [A-]/[HA]

[A-] = [HPO4-2] = [K2HPO4]

[HA] = [H2PO4-] = [KH2PO4]

is you want pH = 7.00

then 7.00 - 7.21 = log [A-]/[HA]

or [A-]/[HA] = 10^-0.21 = 0.62 or [A-] = 0.62[HA]

since A - and HA are equimolar concentrations you can use the 0.62 as a coefficient in the volume of each reagent to use ...

you would need 62 ml of K2HPO4 (A-) and 38 ml of KH2PO4 (HA) to make this buffer.

A microbiologist is preparing a medium on which to culturee. coli bacteria. she buffers the medium at ph 7.00 to minimize the effect of acid-producing fermentation. what volumes of equimolar aqueous solutions of k2hpo4 and kh2po4 must she combine to make 800.0 ml of the ph 7.00 buffer

A microbiologist is preparing a medium on which to culture

e. coli bacteria. she buffers the medium at ph 7.00 to minimize the effect of acid-producing fermentation. what volumes of equimolar aqueous solutions of k2hpo4 and kh2po4 must she combine to make 800.0 ml of the ph 7.00 buffer