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A sample contains of molecules. What is the number of oxygen atoms in the sample? Use
Answer: C. Each molecule contains two oxygen atoms. Thus, oxygen atoms.
A: uses and counts molecules rather than oxygen atoms.
B: counts molecules but omits the two oxygen atoms in each molecule.
D: shifts the amount one place too high, using
Remember: multiply by the number of specified entities in each molecule when counting atoms.
A laboratory checks a powdered reference blend containing only paracetamol and caffeine. The structures of the two compounds are shown in Figure 1.
A sample of the blend has a mass of 1.6754 g and contains a total amount of 0.01000 mol of molecules. A quality-control note states that the two compounds are present in equal masses.
Use Figure 1 and the Ar values in the data booklet to determine the molecular formula and Mr of each compound.
Determine the amount, in mol, of each compound in the sample. Show your reasoning.
Calculate the mass of each compound in the sample and state whether the quality-control note is supported.
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