Question

why does sugar solution becomes alcoholic on adding yest

Answer 1

because yeast cause fermentation in sugar and make it alcoholic.

Answer 2

Answer:

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However, from the yeast's point of view, alcohol and carbon dioxide are waste products, and as the yeast continues to grow and metabolize in the sugar solution, the accumulation of alcohol will become toxic when it reaches a concentration between 14-18%, thereby killing the yeast cells.