buffer solution Write the chemical equation for the reaction that occurred when
ID: 826735 • Letter: B
Question
buffer solution
Write the chemical equation for the reaction that occurred when you added NaOH solutton to the NaH2P04/Na2HP04 buffer solution. Write the chemical equation for the reaction that occurred when you added HCI solution to the buffer solution in (1). Briefly explain why the pH change you observed when you added NaOH solution to distilled water was different from pH changes you observed when you added NaOH solution to the CH3C02H and NaH2P04 solutions. Briefly explain why the pH change you observed when you added HCI solution to distilled water was different from pH changes you observed when you added HCI solution to the NaCH3C02 and Na2HP04 solutions.Explanation / Answer
2.
(1) NaH2PO4(s) + NaOH(aq) = Na3PO4(aq) + H2O(l)
Na2HPO4 + NaOH = Na3PO4 + H2O
(2) NaH2PO4 + HCl = H3PO4 + NaCl
Na2HPO4 + HCl = NaH2PO4 + HCl
3.When NaOH is added to distilled water, the NaOH molecules gets ionised into Na+ and OH- ions making the solution basic.
Whereas in the second case, the OH- ions in NaOH are consumed by the H+ ions released by CH3COOH and NaH2PO4 hence H+ concentration decreases and Ph increases making the solution basic.
But, When these two reactions are compared, the solution in the second case is less basic than the first one. Because the OH- concentration in the second case is less than the first case.
4. When HCl is added to distilled water, the NaOH molecules gets ionised into H+ and Cl- ions making the solution acidic.
Whereas in the second case, the H+ ions in NaOH are consumed by the OH- ions released by CH3COOH and NaH2PO4 hence H+ concentration increases and Ph decreases making the solution acidic.
But, When these two reactions are compared, the solution in the second case is less acidic than the first one. Because the H+ concentration in the second case is less than the first case.
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