If you need specific activity and activity and you already have na, halflife, sample mass and molar mass of the substance, this calculator does the substitution for you. It suits a quick check, a homework answer you want to confirm, or any figure you need to sanity test.
What Is the Radioactive Decay Calculator?
The radioactive decay calculator turns na, halflife, sample mass and molar mass of the substance into specific activity and activity.
It is a quick way to get from the numbers you have to the number you need, without setting up a spreadsheet or reaching for a formula.
How the Radioactive Decay Works
Each result follows from the ones before it, and the calculator shows every step, so a surprising answer can be traced back to the input that caused it.
Round your inputs to the precision you actually know, and keep more precision than that in the intermediate steps.
Getting a Result You Can Trust
Run the calculation twice with slightly different inputs. A sensible calculator moves its output in proportion; a wild change points to a unit or a decimal point problem in what you entered.
Write the inputs down next to the answer. It takes a moment and it is the difference between a number you can explain and one you cannot.
A Worked Example
Working through an example, with na set to 10, halflife set to 5, sample mass set to 2, the calculator returns activity of 0.02773, and specific activity of 0.01. Substitute your own figures and the same steps produce the same kind of answer.
Frequently Asked Questions
What do I need to work out specific activity?
Enter na, halflife, sample mass and molar mass of the substance. The calculator then works through the relationship and reports specific activity and activity.
What does the radioactive decay actually calculate?
It takes na, halflife, sample mass and molar mass of the substance and converts them into specific activity and activity using the standard relationship for this problem. Each step is applied in turn, so every output is traceable back to the numbers you typed in.
How should I enter na?
Use the value you actually have, in the unit shown next to the field. Enter every value in the same unit system. The calculator assumes the figures you supply are consistent, so it cannot correct a mistake that happens before the calculation starts.
Why does a small change in one value move the answer so much?
That happens when an output depends on a ratio, because dividing by a small number magnifies any change in it. Check the units first, then check whether the value you entered is in the range the relationship was designed for.
Do I have to fill in every field?
Only the fields a particular result depends on. If you leave one blank, the results that need it simply show a note instead of a number, and everything else still works.