1. What is the Rate Constant?

The rate constant (k) is a proportionality constant in the rate law that relates the reaction rate to the concentrations of reactants. For first-order reactions, it has units of reciprocal time (s⁻¹).

2. How Does the Calculator Work?

The calculator uses the first-order rate equation:

Where:

• \( [A_0] \) — Initial concentration (mol/L)
• \( [A] \) — Concentration at time t (mol/L)
• \( t \) — Time elapsed (seconds)
• \( \ln \) — Natural logarithm

Explanation: The equation calculates the rate constant from the natural log of the ratio of initial to final concentration divided by the time interval.

3. Importance of Rate Constant

Details: The rate constant is fundamental in chemical kinetics, determining reaction speed and allowing prediction of reaction progress over time.

4. Using the Calculator

Tips: Enter concentrations in mol/L and time in seconds. Initial concentration must be greater than final concentration. All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: What are typical units for first-order rate constants?
A: For first-order reactions, the rate constant has units of s⁻¹ (reciprocal seconds).

Q2: How does temperature affect the rate constant?
A: Rate constants typically increase with temperature according to the Arrhenius equation.

Q3: What's the difference between rate and rate constant?
A: The rate depends on concentrations, while the rate constant is concentration-independent (but temperature-dependent).

Q4: Can this be used for second-order reactions?
A: No, this calculator is specifically for first-order reactions. Second-order reactions use a different equation.

Q5: What's the half-life relation for first-order reactions?
A: For first-order reactions, half-life (t₁/₂) = ln(2)/k and is independent of initial concentration.