[Tutorial: Initial Rates]: This tutorial will guide you through determining a rate law from initial rates. Step 5. Determining the rate constant. The rate law is: Rate =k[A][B]2 The rate constant is determined by substituting in the appropriate concentrations into the rate law and solving for k. This rate constant will allow for different reactions to be compared and for predictions on how fast the reaction will go with different concentrations. Solve for the rate constant. Tap here or pull up for additional resources Tap here or pull up for additional resources