# Half life formula

7/17/2014

02:33 | Author: __Kayla Henderson__

How to Calculate Half Life (with Calculator) - wikiHow

The **half**-**life** of a substance undergoing decay is the time it takes for the amount The **formula** for calculating **half life** is as follows: t1/2 = t * ln(2)/ln(N0/Nt); In this.

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The *half*-*life* of a substance undergoing decay is the time it takes for the amount of the substance to decrease by *half*. It was originally used to describe the decay of radioactive elements like uranium or plutonium, but it can be used for any substance which undergoes decay along a set, or exponential, rate. You can calculate the half-*life* of any substance, given the rate of decay, which is the initial quantity of the substance and the quantity remaining after a measured period of time.

## HALF-LIFE CALCULATOR

5/16/2014

12:26 | Author: __Emma Coleman__

HALF-LIFE CALCULATOR

**Half**-**Life** Calculator, exponential decay, Radioactivity. The above **formulas** are used in calculations involving the exponential decay of radioactive materials.

3/15/2014

02:39 | Author: __Brandon Powell__

Half-lives - Chemwiki

In order to find the **half life** we need to isolate t on its own, and divide it by 2. We would end up with a **formula** as such depict how long it takes.

*Half*-*life*: the amount of time it required for a reaction to undergoing decay by *half*.

Determine its rate constant k?

4. In first order half life, what is the best way to determine the rate constant k? Why?

How much time required for this reaction to be at least 50% and 60% complete?

As in zero and first order reactions, we need to isolate T on its own:

Half-*life* of second order reactions shows concentration vs. time (t), which is similar to first order plots in that their slopes decrease to zero with time.

## Half Life Calculator - MiniWebtool

11/24/2014

06:28 | Author: __Emma Coleman__

Half Life Calculator - MiniWebtool

About This Tool. The online **Half Life** Calculator is used to calculate the **half**-**life** in exponential decay. Half-life Calculation **Formula** in Exponential Decay.

The online Half Life Calculator is used to calculate the *half*-*life* in exponential decay. Definition *Half*-*life* is the period of time it takes for a substance undergoing decay to decrease by half. It is usually used to describe quantities undergoing exponential decay (for example radioactive decay) where the half-life is constant over the whole life of the decay, and is a characteristic unit (a natural unit of scale) for the exponential decay equation. However, a half-life can also be defined for non-exponential decay processes, although in these cases the half-life varies throughout the decay process. The calculation of half-life used in this tool is based on the exponential decay equation. Half-life Calculation *Formula* in Exponential Decay An exponential decay process can be described by the following *formula*: where: N(t) = the quantity that still remains and has not yet decayed after a time t N 0 = the initial quantity of the substance that will decay t 1/2 = the half-life of the decaying quantity.

## Some useful equations for half-lives Nuffield Foundation

9/23/2014

04:25 | Author: __Kayla Henderson__

Some useful equations for half-lives Nuffield Foundation

The solution of this equation is an exponential one where N0 is the initial After one **half life**, the number, N of particles drops to **half** of N0 (the starting value).

The rate of decay of a radioactive source is proportional to the number of radioactive atoms (N) which are present. is the decay constant, which is the chance that an atom will decay in unit time. It is constant for a given isotope. The solution of this equation is an exponential one where N 0 is the initial number of atoms present. Constant ratio This equation shows one of the properties of an exponential curve: the constant ratio property. The ratio of the value, N 1, at a time t 1 to the value, N 2, at a time t 2 is given by: In a fixed time interval, t 2 – t 1 is a constant. Therefore the ratio So, in a fixed time interval, the value will drop by a constant ratio, wherever that time interval is measured. Straight line log graph Another test for exponential decay is to plot a log graph, which should be a straight line. Since Taking natural logs of both sides: Therefore a graph of N against t will be a straight line with a slope of -λ. *Half*-*life* and decay constant The *half*-*life* is related to the decay constant. A higher probability of decaying (bigger λ) will lead to a shorter half-life. This can be shown mathematically. After one half life, the number, N of particles drops to half of N 0 (the starting value). So: By substituting this expression in equation (1) above.

Taking natural logs of both sides gives:

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