# What are the units of activation energy in the Arrhenius equation?

## What are the units of activation energy in the Arrhenius equation?

where k represents the rate constant, Ea is the activation energy, R is the gas constant (8.3145 J/K mol), and T is the temperature expressed in Kelvin. A is known as the frequency factor, having units of L mol-1 s-1, and takes into account the frequency of reactions and likelihood of correct molecular orientation.

### What are the units for activation energy?

The activation energy (Ea) of a reaction is measured in joules per mole (J/mol), kilojoules per mole (kJ/mol) or kilocalories per mole (kcal/mol).

#### What is EA in Arrhenius equation?

The Arrhenius equation is k = Ae^(-Ea/RT), where A is the frequency or pre-exponential factor and e^(-Ea/RT) represents the fraction of collisions that have enough energy to overcome the activation barrier (i.e., have energy greater than or equal to the activation energy Ea) at temperature T.

**Does the pre-exponential factor have units?**

The units of the pre-exponential factor A are identical to those of the rate constant and will vary depending on the order of the reaction. For a first-order reaction, it has units of s−1. For that reason, it is often called frequency factor.

**Is activation energy always positive?**

The activation energy for an elementary chemical reaction is always positive and no one will change that.

## How is EA calculated?

Solution

- Step 1: Convert temperatures from degrees Celsius to Kelvin. T = degrees Celsius + 273.15. T1 = 3 + 273.15.
- Step 2 – Find Ea ln(k2/k1) = Ea/R x (1/T1 – 1/T2) ln(7.1 x 10-2/8.9 x 10-3) = Ea/8.3145 J/K·mol x (1/276.15 K – 1/308.15 K)
- Answer: The activation energy for this reaction is 4.59 x 104 J/mol or 45.9 kJ/mol.

### What is ln A in Arrhenius equation?

A = Frequency factor. Ea= Activation energy. R = Gas constant. T = Kelvin temperature.

#### What does an Arrhenius plot tell you?

Arrhenius plots are often used to analyze the effect of temperature on the rates of chemical reactions. For a single rate-limited thermally activated process, an Arrhenius plot gives a straight line, from which the activation energy and the pre-exponential factor can both be determined.

**Is activation energy negative or zero?**

An elementary reaction can not have a negative activation energy: it must be zero or positive. However, a reaction mechanism that is composed of several steps may have a negative activation energy.

**What’s the difference between EA and Arrhenius equation?**

The only difference is the energy units of Ea: the former form uses energy per mole, which is common in chemistry, while the latter form uses energy per molecule directly, which is common in physics. The different units are accounted for in using either the gas constant, R, or the Boltzmann constant, kB, as the multiplier of temperature T .

## What is the unit of Arrhenius constant k?

The Arrhenius equation is k = Ae^ (-Ea/RT), where A is the frequency or pre-exponential factor and e^ (-Ea/RT) is the fraction of collisions that have enough energy to react (i.e., have energy greater than or equal to the activation energy Ea) at temperature T. What are the units for ln k?

### How to find the slope of the Arrhenius equation?

The value of the slope (m) is equal to -Ea/R where R is a constant equal to 8.314 J/mol-K. “Two-Point Form” of the Arrhenius Equation The activation energy can also be found algebraically by substituting two rate constants (k 1, k 2) and the two corresponding reaction temperatures (T 1, T 2) into the Arrhenius Equation (2).

#### Who is the inventor of the Arrhenius equation?

The Arrhenius equation was put forward by the Swedish chemist Svante Arrhenius in the year 1889. For the decomposition reaction undergone by nitrogen dioxide (given by 2NO 2 → 2NO + O 2 ), a graph plotted with the rate constant (k) on the Y-axis and the absolute temperature (T) on the X-axis is provided below.