A small quantity of an acid is added to a buffer solution composed of H2CO3 and

Question

A small quantity of an acid is added to a buffer solution composed of H2CO3 and NaHCO3. a) write the chemical equation that occurs in the solution when H3O+ is added to the buffer. b) determine the mass of NaHCO3 that Ashlie's be used to prepare this buffer with pH= 7.02 if the concentration of H2CO3 must be 2.25M and the total solution volume is 1.00L. A small quantity of an acid is added to a buffer solution composed of H2CO3 and NaHCO3. a) write the chemical equation that occurs in the solution when H3O+ is added to the buffer. b) determine the mass of NaHCO3 that Ashlie's be used to prepare this buffer with pH= 7.02 if the concentration of H2CO3 must be 2.25M and the total solution volume is 1.00L. a) write the chemical equation that occurs in the solution when H3O+ is added to the buffer. b) determine the mass of NaHCO3 that Ashlie's be used to prepare this buffer with pH= 7.02 if the concentration of H2CO3 must be 2.25M and the total solution volume is 1.00L.

Explanation / Answer

a)

H2CO3 -------- H+ + HCO3-

Na+ + HCO3- ----------- NaHCO3

b)

pKa of H2CO3 = 6.346

Using the hessley henderbach equation

pH = pKa + log[NaHCO3/H2CO3]

7.02 = 6.346 + log[NaHCO3/H2CO3]

NaHCO3 = 4.709 * 2.25 = 10.596 moles

Molar mass of NaHCO3 = 23 + 1 + 12 + 48 = 84 gm/mol

Mass of NaHCO3 = 10.596 mol * 84 gm/mol = 890.14 gms

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