The Atom $40 \mathrm {~K}$ Decays Radioactively to the Gas $40 \mathrm { Ar }$

question 13

Multiple Choice

The atom $40 \mathrm {~K}$ decays radioactively to the gas $40 \mathrm { Ar }$ . An ancient rock is found to contain enough $40 \mathrm { Ar }$ gas to indicate that $77.0 \%$ of the $40 \mathrm {~K}$ in the rock has decayed to $40 \mathrm { Ar }$ ince the rock solidified. (Any previous argon would have boiled out of liquid rock.) How long ago did the rock solidify? The half-life of $40 \mathrm {~K}$ is $1.25$ billion years.

• A) \(0.471\) billion years
• B) \(2.65\) billion years
• C) \(0.324\) billion years
• D) \(1.80\) billion years

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Definitions:

Conduct Disorder

A mental disorder diagnosed in childhood or adolescence characterized by a longstanding pattern of disregard for the rights of others.

Juvenile Delinquency

Illegal or antisocial behaviors carried out by individuals under the age of majority.

Passive-aggressive Disorder

A pattern of indirectly expressing negative feelings instead of openly addressing them, marked by passive resistance and avoidance.

Aggressive Behavior

A pattern of behavior aimed at causing harm or intimidation to others.