APFIVE Which of the following pieces of evidence best supports the conclusion that calcium nitrate, $$\text{Ca(NO}_{3}\text{)}_{2}$$, contains approximately 17.1% nitrogen by mass?
Adding the atomic masses of calcium and nitrogen without considering the nitrate group, resulting in an erroneous percentage.
Multiplying the nitrogen atomic mass by two and then adding the mass of oxygen, without proper division by total mass, misrepresenting the percent composition.
Calculating total molar mass as $$40.078 + 2*(14.007+ 3*16) = 164.092\,g/mol$$ and then computing percent nitrogen as $$\frac{2*14.007}{164.092} \times 100 \approx 17.1\%$$.
Using only the molar mass of nitrogen, $$14.007\,g/mol$$, divided by the molar mass of calcium, which yields an irrelevant ratio.
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