`D_R = k*[A]`

Enter a value for all fields

The Rate of Decay calculator computes the rate of decay based on a rate constant for the radionuclide and concentration of decaying radionuclide after a period of time.

INSTRUCTIONS: Choose units and enter the following:

• (k) Rate Constant for the Radionuclide. Decay per unit of time (e.g. 3.2 per day)
• ([A])  Concentration or amount of Decaying Radionuclide after a period of time (e.g. 23.5 moles per Liter).

Rate of Decay (D_R):  The rate is returned in mole per liter per day. 

The Math / Science

The equation for Rate of Decay calculates the rate at which a radioactive substance will break down according to the laws of first order kinetics. This process obeys first order kinetics because the rates of radioactive decay are independent of temperature, but dependent on concentration. The Rate of Decay equation is:

       `D_R = k*[A]`

where:

• D_R = rate at which a radioactive substance will breakdown
• k = rate constant for the radionuclide
• [A] = concentration/amount of decaying radionuclide after time “t”
   

The rate of decay should be in units of amount/time. The rate constant, k, will be in units of time^-1, and [A] will have units of an amount (moles, moles/liter, grams, kilograms…etc.).

Supplemental Materials

UCDavis ChemWiki: Rate Law

Khan Academy: Rate Law and Reaction Order

References

Whitten, et al. "Chemistry" 10th Edition. Pp. 863