<prompt> A buffer that is most effective at a pH of about 4.5 is;Acetate buffer.Bicarbonate bufferPhosphate bufferTris buffer  <response>: Ans. is a i.e. Acetate BufferRef Guyton, 10e, p349A buffer system is most effective when the pH of the system is near its pka valueLets see the pka of the buffers given in the questionBufferPkaPhosphateBicarbonateAcetateTris 6.8 6.14.76 Harper 25the p24 8.3 Harper 25thep23 Its the acetate buffer which has its pka 4.76 value nearest to the pH of the system 4.5, hence it will be most effective at this pH. 