Westonci.ca is the premier destination for reliable answers to your questions, brought to you by a community of experts. Discover a wealth of knowledge from professionals across various disciplines on our user-friendly Q&A platform. Explore comprehensive solutions to your questions from knowledgeable professionals across various fields on our platform.

Element X is a radio isotope with half lives of 11 yrs. The initial mass of element x is 60 grams. How much to the nearest tenth of the element remains after 25 yrs?

Sagot :

We are given that a radio isotope has an initial mass of 60 grams and a half-life of 11 years. The mass of the isotope with respect to time can be modeled using the following exponential function:

[tex]M=m_0e^{kt}[/tex]

Where:

[tex]\begin{gathered} M=\text{ mass} \\ m_0=\text{ initial mass} \\ k=\text{ constant} \\ t=\text{ time} \end{gathered}[/tex]

Now, since we are given that the half-life is 11 years this means that the mass will be half of the initial mass when "t = 11 years". We can use this fact to calculate the value of "k". Substituting half the initial mass we get:

[tex]\frac{m_0}{2}=m_0e^{k(11\text{year)}}[/tex]

Now, we may cancel the initial mass:

[tex]\frac{1}{2}=e^{k(11\text{years)}}[/tex]

Now, we solve for "k". To do that we will take natural logarithm to both sides:

[tex]\ln \frac{1}{2}=\ln e^{k(11\text{years)}}[/tex]

Now, we use the following property of logarithms:

[tex]\ln x^y=y\ln x[/tex]

Applying the property we get:

[tex]\ln \frac{1}{2}=k(11years)\ln e^{}[/tex]

We have that:

[tex]\ln e=1[/tex]

Therefore:

[tex]\ln \frac{1}{2}=k(11years)[/tex]

Now, we divide both sides by 11:

[tex]\frac{1}{11}\ln \frac{1}{2}=k[/tex]

Solving the operations:

[tex]-0.063=k[/tex]

Now, we substitute in the formula for the mass:

[tex]M=60e^{-0.063t}[/tex]

Now, to determine the value of the mass after 25 years we substitute the value "t = 25", we get:

[tex]M=60e^{-0.063(25)}[/tex]

Solving the operations:

[tex]M=12.4[/tex]

Therefore, the mass after 25 years is 12.4 grams.