QuestionAugust 21, 2025

Question 3 (1 point) Isotopic abundances are different in other parts of the universe. Suppose that on planet Krypton we find the following stable isotopes and abundances for boron: {}^10B(10.013amu) 65.75% {}^11B(11.009amu) 25.55% {}^12B(12.014amu) 8.70% What is the value of the average atomic mass of boron on planet Krypton in amu? Answer with 3 decimal places. Do not include the unit in your answer. Your Answer: square

Question 3 (1 point) Isotopic abundances are different in other parts of the universe. Suppose that on planet Krypton we find the following stable isotopes and abundances for boron: {}^10B(10.013amu) 65.75% {}^11B(11.009amu) 25.55% {}^12B(12.014amu) 8.70% What is the value of the average atomic mass of boron on planet Krypton in amu? Answer with 3 decimal places. Do not include the unit in your answer. Your Answer: square
Question 3 (1 point) Isotopic abundances are different in other parts of the universe. Suppose that on planet Krypton we find the following stable isotopes and abundances for boron: {}^10B(10.013amu) 65.75% {}^11B(11.009amu) 25.55% {}^12B(12.014amu) 8.70% What is the value of the average atomic mass of boron on planet Krypton in amu? Answer with 3 decimal places. Do not include the unit in your answer. Your Answer: square

Solution
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Answer

10.442 Explanation 1. Convert percentages to decimals Convert each percentage to a decimal by dividing by 100: 65.75\% = 0.6575, 25.55\% = 0.2555, 8.70\% = 0.0870. 2. Calculate weighted average Use the formula for average atomic mass: **\text{Average Atomic Mass} = \sum (\text{isotope mass} \times \text{abundance})**. Compute: - For {}^{10}B: 10.013 \times 0.6575 = 6.5835575 - For {}^{11}B: 11.009 \times 0.2555 = 2.8127995 - For {}^{12}B: 12.014 \times 0.0870 = 1.045218 3. Sum the contributions Add the results from Step 2: 6.5835575 + 2.8127995 + 1.045218 = 10.441575.

Explanation

1. Convert percentages to decimals<br /> Convert each percentage to a decimal by dividing by 100: $65.75\% = 0.6575$, $25.55\% = 0.2555$, $8.70\% = 0.0870$.<br /><br />2. Calculate weighted average<br /> Use the formula for average atomic mass: **$\text{Average Atomic Mass} = \sum (\text{isotope mass} \times \text{abundance})$**.<br /> Compute: <br />- For ${}^{10}B$: $10.013 \times 0.6575 = 6.5835575$<br />- For ${}^{11}B$: $11.009 \times 0.2555 = 2.8127995$<br />- For ${}^{12}B$: $12.014 \times 0.0870 = 1.045218$<br /><br />3. Sum the contributions<br /> Add the results from Step 2: $6.5835575 + 2.8127995 + 1.045218 = 10.441575$.
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