A solution which has a pH of 1 is mixed with a solution of pH 7. What will the colour of universal indicator be in a mixture of two solutions?

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t-nez | High School Teacher | (Level 3) Associate Educator

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This will depend on the amounts of the two solutions that are mixed and what the solutions contain. The pH 7 solution is neutral, so it would give universal indicator a color of green. The pH 1 solution is very acidic and would produce a dark red color with universal indicator. If equal volumes of the solutions are mixed and neither has any buffering capacity we would expect a new pH of about 4, so the color of universal indicator would be orange. If the amounts aren't equal or if buffering takes place (buffers resist changes in pH), then it would be hard to predict the final color but it would be somewhere between pH 1 and 7 so the color would most likely be orange or yellow. The attached image shows the color range of universal indicator.

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