Where the
world gathers for metal finishing
Q&As since 1989


-----

How Temperature Affects the Speed of a Chemical Reaction

My daughter is doing a science project again and needs your help. You have helped us in the past . Thank you . Her new project is . To determine how temperature affects the speed of a chemical reaction. if you can help her .That would be great.

Thanks again,

Peggy Lasala
- West Babylon, New York
2003

---

See 15572. Temperature effects are explained in association with the reaction between magnesium and different acids

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2002

---

2003

Do an Internet search for Arrhenius equation. This equation gives the temperature dependence of most reaction rate factors. It is named for its discoverer, Svante August Arrhenius, a Swedish chemist and high school teacher who won the 1903 Nobel Prize for chemistry.

The equation is written:

k = A x e^(-Ea/RT)

where k is the reaction rate constant, A is a constant, e is the base of natural logarithms, Ea is the activation energy, R is the gas constant, and T is the temperature (in degrees Kelvin). Note: 'e is raised to the power (-Ea/RT).' The basis for this reaction is the concept of transition state: for atoms or molecules to go from one stable compound to another, they must gain an activation energy (such as by heating) to allow breaking of the interatomic bonds in the first compound, which is then followed by the formation of bonds in the new compound.

Since calculators and computers were not around when Arrhenius did his experiments, he used the mathematical properties of logarithms. By plotting on paper the logarithm of the reaction rate, ln (k), versus 1/T, he found rates from different temperatures gave a straight line:

ln (k) = ln (A) + B x 1/T

In mathematical parlance, B is the slope of the line, and ln (A) is the intercept. Arrhenius was smart enough to figure out that B represented -Ea/R. Now, as the temperature gets higher, the negative term (-Ea/RT) gets smaller, so ln (k) increases. Because of this, the reaction rate is said to increase exponentially with temperature.

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.