Asked by 01236
A piece of lithium metal is added to a beaker that contains water and phenolphthalein. Using what you know about the properties of bases, choose the best explanation for what you observe.
The phenolphthalein is turning pink because an acid is forming.
The phenolphthalein is turning pink because a base is forming.
The phenolphthalein is turning pink because the reaction is at equilibrium.
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The phenolphthalein is turning pink because a base is forming.
Reason: lithium reacts with water to give lithium hydroxide and hydrogen gas: 2 Li + 2 H2O → 2 LiOH + H2. LiOH is a strong base, raising the pH; phenolphthalein is colorless in neutral/acidic solution and turns pink in basic solution (pH ≳ 8.2). The effect is not due to an acid or simply being at equilibrium.
Reason: lithium reacts with water to give lithium hydroxide and hydrogen gas: 2 Li + 2 H2O → 2 LiOH + H2. LiOH is a strong base, raising the pH; phenolphthalein is colorless in neutral/acidic solution and turns pink in basic solution (pH ≳ 8.2). The effect is not due to an acid or simply being at equilibrium.
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