Interpreting Data

Interpreting Datavideo

Interpreting Data

• Data recorded in rate studies is used to plot graphs to calculate the rate of a reaction

• Plotting a graph until the completion of the reaction shows how the rate changes with time

• Over time the rate of reaction slows as the reactants are being used up so the line becomes less steep and eventually becomes horizontal, indicating the reaction has finished

• You can plot more than one run of a variable on the same graph making it easier to see how the variable influences the rate

  • For example, plotting the effect of concentration on a reaction between the acid and marble chips

    

• The steeper the curve, the faster the rate of the reaction

• The curve is steepest initially so the rate is quickest at the beginning of the reaction

• As the reaction progresses, the concentration of the reactants decreases and the rate decreases shown by the curve becoming less steep

• When one of the reactants is used up, the reaction stops, the rate becomes zero and the curve levels off to a horizontal line

• The amount of product formed in a reaction is determined by the limiting reactant:

  • If the amount of limiting reactant increases, the amount of product formed increases

  • If the amount of the reactant in excess increases, the amount of product remains the same

• Drawing a tangent to the slope allows you to show the gradient at any point on the curve

• The steeper the slope, the quicker the rate of reaction

• The volume of a gaseous product would increase to a maximum over time, so the line levels out indicating the reaction is over

• Since the volume and mass would be proportional, this could also be a graph of the mass of product versus time

Calculating the Rate of Reaction at a Particular Point 

• To do this you need to find the gradient of the curve at that point

• To do this a tangent is drawn to the curve and then the gradient of the tangent calculated