Question

 

Pre-Lab Questions

1. Describe at least two factors that can affect the rate of a chemical reaction.
2. Describe the chemical reaction occurring in a glowstick. What type of reaction is it? How do you know a chemical reaction is occurring? What is the role of the dye?
3. Using the “If ___, then ___” format, write a hypothesis to predict what will occur to a glow stick if you change its temperature.
4. The decomposition of H₂O₂ is a first-order reaction given by the formula: Rate = k [H₂O₂]¹. How would the reaction rate be affected if the H₂O₂ concentration were double its original value?

experiment 1: temperature and the rate of chemical reaction

Data Sheet

Table 1. Temperature vs. Brightness of Glow Stick

Beaker	Temperature (ºC)	Brightness Before Activation	Brightness After Activation	Start Time	Stop Time
Beaker 1 (Room Temp)
Beaker 2 (Cold Water)
Beaker 3 (Hot Water)

Graph of Your Data:

Post-Lab Questions

1. Was your hypothesis supported or rejected? Use your data to support your reasoning.
2. What was the independent variable in the experiment?
3. What was the dependent variable in the experiment?
4. What are some human errors that could have affected your results?
5. What is the correlation between the brightness of the glow stick and the reaction rate?
6. How does the temperature surrounding the glow stick affect the observed brightness? Use your data to support your answer.

Answer 1

* 1. Reactant concentration. Increasing the concentration of one or more reactants will often increase the rate of reaction. This occurs because a higher concentration of a reactant will lead to more collisions of that reactant in a specific time period.

2.Temperature. An increase in temperature typically increases the rate of reaction. An increase in temperature will raise the average kinetic energy of the reactant molecules. Therefore, a greater proportion of molecules will have the minimum energy necessary for an effective collision .

* The glow stick contains two chemicals, a base catalyst, and a suitable dye (sensitizer, or fluorophor). This creates an exergonic reaction. The chemicals inside the plastic tube are a mixture of the dye, the base catalyst, and diphenyl oxalate. The chemical in the glass vial is hydrogen peroxide.

*A chemical reaction is usually accompanied by easily observed physical effects, such as the emission of heat and light, the formation of a precipitate, the evolution of gas, or a color change. Absolute confirmation of a chemical change can only be validated by chemical analysis of the products.

*This allows the inside the glass to mix with the chemicals outside the glass vial. Once these chemicals contact one another, a reaction takes place. The chemical reaction in a glow stick releases energy in the form of light. This light along with dye allows the stick to glow the brilliant colors that we observe.

* Decomposition of H2O2 is a first order reaction. So the rate = K[H2O2]

Now we assume initially the concentration of H2O2 is 'X' M.

So rate =K × X

Now when the concentration is double it's original value i. e. [H2O2] = 2X Then,

Rate = K[H2O2] =K ×2X=2KX

Therefore if the concentration of H2O2 is double it's original value the rate of the reaction will be double.