Question

consider the percent abundance of the isotopes of element x.
what is the average atomic mass of x? calculate the average atomic mass then choose your answer.
between 24 and 25
24
between 25 and 26
25

Explanation:

Step1: Recall the formula for average atomic mass

The formula for average atomic mass is the sum of (mass of isotope × percent abundance (in decimal)) for each isotope. So, we first convert the percent abundances to decimals by dividing by 100.
For \(^{24}\text{X}\): percent abundance = \(80\% = \frac{80}{100}=0.8\)
For \(^{25}\text{X}\): percent abundance = \(10\%=\frac{10}{100} = 0.1\)
For \(^{26}\text{X}\): percent abundance=\(10\%=\frac{10}{100}=0.1\)

Step2: Calculate the contribution of each isotope

• Contribution of \(^{24}\text{X}\): \(24\times0.8 = 19.2\)
• Contribution of \(^{25}\text{X}\): \(25\times0.1=2.5\)
• Contribution of \(^{26}\text{X}\): \(26\times0.1 = 2.6\)

Step3: Sum the contributions

Now, we sum up these contributions to get the average atomic mass: \(19.2 + 2.5+2.6=24.3\)

Answer:

Between 24 and 25