A 42.7 gram sample of potassium nitrate (KNO_3) contains how many grams of potassium?

• A. 8.32 grams
• B. 42.7 grams
• C. 13.9 grams
• D. 25.0 grams

Answer: (A)

Verified step by step guidance

1. Identify the chemical formula of potassium nitrate, which is KNO\_3, and note that it contains one potassium (K) atom per formula unit.
2. Calculate the molar mass of KNO\_3 by summing the atomic masses of potassium (K), nitrogen (N), and three oxygen (O) atoms: \(M_{KNO_3} = M_K + M_N + 3 \times M_O\).
3. Determine the mass percentage of potassium in KNO\_3 using the formula: \(\%K = \left( \frac{M_K}{M_{KNO_3}} \right) \times 100\).
4. Use the mass percentage to find the mass of potassium in the 42.7 gram sample by multiplying: \(\text{mass of K} = \left( \frac{\%K}{100} \right) \times 42.7\) grams.
5. Interpret the result as the grams of potassium contained in the 42.7 gram sample of potassium nitrate.