Answer :
A buffer solution containing 105 mL of formic acid with a concentration of 0.64 mol/L needs 0.45 g of solid sodium formate to achieve a pH of 3.93.
Where is buffer solution used?
To keep the pH neutral or even slightly alkaline, buffer solutions are employed in the production of many cosmetic and personal hygiene products. The buffer solution stops the items from getting either too acidic or too alkaline, which could irritate the skin.
Briefing:
Since sodium formate is a powerful electrolyte, its concentration must be 0.64 M, the same as that of formate.
We can use the following expression to determine how much sodium formate is needed.
[tex][H C O O N a]=\frac{\text { mass HCOONa }}{M W(H C O O N a) \times \text { liters of solution }}[/tex]
Mass HCOONa = (HCOONa) * MW (HCOONa) * litres of solution
Mass HCOONa = 0.64 mol/L * 68.01g/mol *0.0105 = 0.45 g
A buffer solution containing 105 mL of formic acid with a concentration of 0.64 mol/L needs 0.45 g of solid sodium formate to achieve a pH of 3.93.
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The complete question is-
What mass of solid sodium formate (of MW 68.01) must be added to 105 mL of 0.64 mol/L formic acid (HCOOH) to make a buffer solution having a pH of 3.93? Ka = 0.00018 for HCOOH.
