When a breath sample is passed through limewater, the solution becomes cloudy because the breath contains which gas?

Prepare for the NLN PAX Science Exam with flashcards and multiple choice questions. Each question includes hints and detailed explanations to boost your confidence and exam readiness.

Multiple Choice

When a breath sample is passed through limewater, the solution becomes cloudy because the breath contains which gas?

Explanation:
Limewater clouds when carbon dioxide is present. This test uses calcium hydroxide solution; carbon dioxide reacts with it to form calcium carbonate, which is insoluble and appears as a milky precipitate. In the breath, carbon dioxide is produced by metabolism, so exhaled air contains CO2. When CO2 bubbles through limewater, the reaction occurs: CO2 + Ca(OH)2 → CaCO3 + H2O, yielding the cloudy suspension. Hydrogen, oxygen, and nitrogen from breath do not form this precipitate with limewater, so they don’t produce the cloudiness. The gas responsible for the cloudy limewater is carbon dioxide.

Limewater clouds when carbon dioxide is present. This test uses calcium hydroxide solution; carbon dioxide reacts with it to form calcium carbonate, which is insoluble and appears as a milky precipitate. In the breath, carbon dioxide is produced by metabolism, so exhaled air contains CO2. When CO2 bubbles through limewater, the reaction occurs: CO2 + Ca(OH)2 → CaCO3 + H2O, yielding the cloudy suspension. Hydrogen, oxygen, and nitrogen from breath do not form this precipitate with limewater, so they don’t produce the cloudiness. The gas responsible for the cloudy limewater is carbon dioxide.

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