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Universal indicator in potassium hydroxide
Potassium hydroxide solution is produced when potassium reacts with water.
What is the colour of universal indicator when added to potassium hydroxide solution? Give one reason for your answer.
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Marking points
- 1 Colour field gives blue, violet or purple.
- 2 Reason field identifies potassium hydroxide solution as alkaline/basic or containing hydroxide ions.
Full-mark answer
Colour of universal indicator: purple. Reason: potassium hydroxide solution is alkaline because it contains hydroxide ions, OH⁻.
Why this answer loses marks
The indicator is red because potassium reacts strongly.
Reactivity does not set the indicator colour; use the hydroxide solution’s alkalinity.