Answer
(a) yellow because the PH value is low (within the acid range).
(b) yellow since the PH value of the formed buffer solution $\mathrm{CH_3COOH/CH_3COO^-}$ is about 5.
(c) yellow; the buffer completely neutralizes the small amount of added $\mathrm{OH^-}$
(d)red; the solution becomes basic because the buffer no longer retains the PH value.
Work Step by Step
(a) yellow because the PH value is low (within the acid range).
(b) yellow since the PH value of the formed buffer solution $\mathrm{CH_3COOH/CH_3COO^-}$ is about 5.
(c) yellow; the buffer completely neutralizes the small amount of added $\mathrm{OH^-}$
(d)red; the solution becomes basic because the buffer no longer retains the PH value.
