Could you explain too? Thanks! Chemical Formula CH3COOH NH3 H2CO HCO3 Dissociati

Question

Could you explain too? Thanks!

Chemical Formula CH3COOH NH3 H2CO HCO3 Dissociation Constant K=1.8x10-5 1.8 × 10-5 K/ = 4x10-7 K2 4 x 10-11 A buffer solution is prepared by mixing equal volumes of 0.50 M weak acid with 1.0 M of its conjugate base. Based on the data given in the table above, which of the following pairs of chemical solutions should be used to prepare the buffer solution so that the pH will be between 4 and 7? 23. A) CH,COOH and NH3 B) CH,COOH and CH COONa C) H2CO3 and NH D) H2CO3 and Na2 CO

Explanation / Answer

Acid buffer solution is a mixture of weak acid and it's salt with strong base

CH3COOH + CH3COONa is acid buffer solution

Ka of CH3COOH

Pka   = -logKa

        = -log1.8*10^-5

        = 4.75

conc of conjugate base CH3COO^-   = 1M

conc of weak acid   CH3COOH          = 0.5M

PH    = PKa +log[CH3COO^-]/[CH3COOH]

         = 4.75 + log1/0.5

         = 4.75 + 0.3010

           = 5.051

B. CH3COOH and CH3COONa

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