The atomic mass of rhenium is 186.2 amu. It has two naturally occurring isotopes. Given that 37.1% of natural rhenium is rhenium–185, what is the other stable isotope?单项选择题
A
190 75 Re
B
183 75 Re
C
187 75 Re
D
181 75 Re
E
189 75 Re

Question

The atomic mass of rhenium is 186.2 amu.  It has two naturally occurring isotopes. Given that 37.1% of natural rhenium is rhenium–185, what is the other stable isotope?

BlackTom AI · Accepted Answer

The problem gives the atomic mass of rhenium as 186.2 amu and that natural rhenium is 37.1% rhenium-185. The remaining 100% − 37.1% = 62.9% must be the other stable isotope.

First, convert percentages to decimals: 0.371 for Re-185 and 0.629 for the other isotope.

Use the average atomic mass formula: (fraction of isotope 1) × (mass number of isotope 1) + (fraction of isotope 2) × (mass number of isotope 2) = average atomic mass.

Plugging in the known values: 0.371 × 185 + 0.629 × (mass number of the other isotope) = 186.2.

Calculate the contribution of Re-185: 0.371 × 185 = 68.635 amu.

Subtract this from the total average mass to find the contribution needed from the other isotope: 186.2 − 68.635 = 117.565 amu.

Now solve for the mass number of the other isotope: (mass number of the other isotope) = 117.565 ÷ 0.629 ≈ 187.0.

The calculation yields a mass number very close to 187, which corresponds to the isotope listed as 187/75 Re in the options.

Evaluating the other choices quickly:
- 190/75 Re would contribute too much to the average mass given the 0.629 fraction, not matching 186.2.
- 183/75 Re would contribute too little to reach 186.2 with the 0.629 fraction.
- 181/75 Re and 189/75 Re similarly fail to reproduce the given average when weighted by 0.629 and 0.371.

Therefore, the combination that satisfies the mass balance with the given abundance is the isotope with mass number 187.

The atomic mass of rhenium is 186.2 amu. It has two naturally occurring isotopes. Given that 37.1% of natural rhenium is rhenium–185, what is the other stable isotope?单项选择题

类似问题

An atom of Beryllium isotope has in its nucleus

Which of the following best describes an Isotope?

How many protons, neutrons and electrons are in selenium − 77?

When we describe different isotopes of the same element, such as Carbon-12, Carbon-13, and Carbon-14, what is the main difference between them?

Why do different isotopes of the same element have similar chemistry?

Which pair represents a set of isotopes?

Isotopes of an element differ in that they have the same number of [ Select ] neutrons protons but different numbers of [ Select ] neutrons protons .

Isotopes of an element differ in that they have the same number of protons but different numbers of neutrons .

更多留学生实用工具

智能学习助手

风格化写作助手

论文查重助手

文献引用助手

课堂转译助手

课堂笔记助手

Quiz搜索助手

学校历年真题

智能刷题助手

智能匹配练习

希望你的学习变得更简单