Chapter 2.5, Problem 2Q

Interpretation Introduction

Interpretation: The atomic weight of oxygen should be determined using the given conditions that the isotopes ${}^{16}O$ has a mass of $\text{15}\text{.9949u}$ in an abundance $\text{99}\text{.763\%}$, ${}^{17}O$ has a mass of $16.9991u$ in an abundance $\text{0}\text{.0375\%}$ and ${}^{18}O$ has a mass of $17.9991u$ in an abundance of $\text{0}\text{.1995\%}$.

Concept introduction:

Equation for average weight is,

    $\begin{array}{l}\text{average weight}\text{=}\left(\frac{\text{\%abundance}\text{isotope-1}}{\text{100}}\right)\text{×}\text{(mass}\text{of}\text{isotope-1)}\\ \text{+}\left(\frac{\text{\%abundance}\text{isotope-2}}{\text{100}}\right)\text{×}\text{(mass}\text{of}\text{isotope-2)}\text{+}\text{etc}\end{array}$

Two species are said to be isotopes if both have same atomic number but different mass number.