An unknown substance turns blue litmus paper to red. which additional test could be used to confirm the substance’s identity?
it should turn phenolphthalein from colorless to pink because it is a base.
it should turn phenolphthalein from pink to colorless because it is a base.
it should turn methyl orange to orange because it is an acid.
it should turn methyl orange to red because it is an acid.

The correct answer is the first one : It should turn phenolphthalein from colorless to pink because it is a base.

Explanation:

because

The additional test could be used to confirm the substance's identity is that It should turn phenolphthalein from colorless to pink because it is a base.

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Option (d) is the correct answer.

Explanation:

When a substance changes blue litmus into red then it means the substance is acidic in nature.

Whereas when a substance changes red litmus into blue then it means the substance is basic in nature.

When a base is added in phenolphthalein then color of phenolphthalein will change from colorless to pink. Whereas on adding an acid, phenolphthalein will remain colorless.

On the other hand, methyl orange will change its color from orange to red on addition of an acid. And, methyl orange will change its color from orange to yellow on addition of a base.

Therefore, we can conclude that an additional test that could be used to confirm the substance’s identity is that it should turn methyl orange to red because it is an acid.