Rates of Reaction

Rates of ReactionAdrian, Fraser, Roderick, Emma

IntroductionDefine1) Reaction

-Indications

2) Rate of ReactionInfluencing factors:-Concentration -Temperature-Catalyst

Objective• Determine how concentration, temperature

and catalysts affect the rate of reaction

Experiments Materials: Chemical Materials: Equipment

Materials: Safety

1 -Temperature

- 3 Alka-Seltzer Tablets

- Hot, cold and room temperature water

- 3 beakers- Measuring cup- Thermometer- stopwatch

-Safety goggles

2 -Concentration

- Vinegar- Water- Baking soda

- 6 beakers- Dropper- measuring cup- Measuring

spoons- Stopwatch- stirring rod

-Safety goggles

3 -Catalysts

- Manganese Dioxide- Hydrogen Peroxide

- 2 test tubes- 2 balloons- stopwatch

-Safety goggles

Materials

Safety Precautions

• Wear safety goggles at all times• Long hair tied back• Wash hands before and after each

experiment

Third Experiment: Catalyst• Chemicals used are explosive• No open flames

TEMPERATURE

Experiment: Temperature• How does

Temperature affect the rate of reaction?

• Alka-Seltzer tablets in different temperatures of water

Temperature: Procedure1) Place 250 mL of water into a

beaker2) Record the temperature3) Gently place the tablet into the

beaker4) Record the time taken to dissolve5) Repeat for hot and cold water

Temperature: Observations

Water type(exact temp)

Time to be dissolved Other Observations

Hot62 oC

17.34 seconds-Large bubbles

-Loud fizzing sound

Room Temp24 oC

52.24 seconds-Many bubbles

-Softer fizzing sound

Cold6 oC

104.52 seconds-Small bubbles

-Soft fizzing sound

Temperature: Actual Affects• When the temperature of a substance rises,

the particles gain energy• With more energy, the particles move faster

• They then collide with the other substance at an increased rate

• Less time for the reaction to occur

Sources of Error• Temperature

– Recorded values could be out

• Exact Time– Hard to tell the tablet had

completely dissolved

Modifications for the Future

For more accurate results:– Conduct the 3

trials at once– Add more

temperatures to test

Temperature: Conclusion

• Temperature directly affects the rate of reaction.

temperature = particle movement particle movement = collision collision = rate of reaction

• Opposite occurs for a decrease in temperature

CONCENTRATION

Concentration Experiment

• Particle Collision theory: explains how reactions occur, and why there are different rates of reactions based on differences of characteristics

Concentration Experiment• Concentration: the amount of a given solute in a

solution

• Concentration = number of moles / Volume of solution (L)

• Unit = mol / L or M

• Can also be calculated in Volume / Volume percentage. (Volume of solute / Volume of Solution)

Procedure• Part A:

1) Tablespoon of baking soda in beaker

2) Mix together 10 mL of vinegar with 5 drops of water

3) Pour the vinegar/water mixture into baking soda

4) Observe and record

Procedure• Part B:

1) Place a tablespoon of baking soda in beaker

2) Mix together 5 mL of water with 5mL of vinegar

3) Pour the vinegar/water mixture into baking soda

4) Observe and record

• Part C:

1) Place a tablespoon of baking soda in beaker

2) Mix together 10 mL of water and 5 drops of vinegar

3) Pour the vinegar/water mixture into the baking soda

4) Observe and record

Procedure

Observations• The reaction that took place was

seen like the one shown below

ObservationsVinegar vs Water Molarity (mol/L) Time (seconds) Qualitative Observations

High Concentration

10 mL vinegar

5 drops of water

0.853 M 15.7 Bubbles Formed

Fizzing

No baking soda leftover

Medium Concentration 5 mL vinegar

5 mL water

0.4375 M 20.95 Less bubbles

Less fizzing

Some baking soda leftover

Low Concentration

5 drops of vinegar

10 mL water

0.0213 M 23.66 Even less bubbles

Even less fizzing

More baking soda leftover

Sources of error• Time recorded not exact

– Hard to see whether reaction complete

• Impurities could have resulted in differences in reaction

How concentration affects rate of reaction• Higher concentration = more particles of

reactants available• More particles = higher frequency• Higher frequency = faster rate of reaction• Concentration is in direct relation to Rate of

reaction

Concentration affecting rate of reaction

Simulation of Concentration affecting the rate of reaction:

http://www.animatedscience.com.au/learningmodules/collision.swf

Modifications to Experiment• Run all three tests at the same time

– Allows for better comparison • More trials

– If more tests were conducted = accurate trend

Conclusion• Concentration in direct relation to

Rate of reaction• Higher concentration allows more

collisions• Lower concentration limits collisions

Application of Concentration• Cleaning detergents

– Concentrated soluble soaps such as laundry soaps

CATALYSTS

Experiment: CatalystDefine Catalyst:

• changes the minimum energy needed for a reaction to occur

• is not consumed by the reaction

Catalyst in Our Experiment • Decomposition of Hydrogen

Peroxide2 H2O2 (aq) + MgO2 (s) → O2(g) + 2 H2O(l) + MgO2 (s)

Hydrogen peroxide Manganese dioxide

Procedure• Part A

– Hydrogen Peroxide in test tube

– Place balloon on top

• Part B– Hydrogen Peroxide and

Manganese Dioxide in test tube

– Place balloon on top

ObservationsPresence of catalyst

Time Inflation of balloon

General observations

No catalyst(5 mlHydrogenPeroxide)

30 sec None Nothing happened

CatalystManganese dioxide with 5 ml hydrogen peroxide

5 sec

10 sec

•Slight inflation of balloon•Production of heat

•Balloon went upright, inflated slightly•Test tube got hot

Error and Modifications• Oxygen gas could have escaped• Contaminants

• Measure exact quantities used• Measure size of inflation (diameter)

Conclusion• By itself, the decomposition of hydrogen

peroxide into water and oxygen is slow• Manganese dioxide allows this

decomposition to take place rapidly• The oxygen produced inflated the balloon

on the test tube

2 H2O2 (aq) + MgO2 (s) → O2(g) + 2 H2O(l) + MgO2 (s)

Applications of CatalystsChemical Industry:-more $$ if they make products faster

Ex.-Manufacturers of Nitric Acid use

catalyst: Platinum-Very expensive metal, but only need

small quantity which can be reused

Estimate: -90% all commercially produced

chemical products involve catalysts at some stage

Other: -Energy Processing

-Bulk/Fine Chemicals-Food Processing

Rate of Reaction: Overall Conclusion

• It was shown form the three experiments that temperature, concentration and the presence of catalysts, affect the rate of reaction

Concentration and Temperature-the higher the concentration or temperature, the faster the reaction takes place

Catalysts-the presence of positive catalysts, such as Manganese Dioxide, speeds the rate of reaction

Further research

Conduct more experiments-Surface Area-Pressure-Negative catalysts-other factors

Questions?

No Questions.

Perfect.

Now we have some questions for you.

What is the definition of a reaction?

• Summarize the temperature experiment.

What is the reason behind the rate of reaction changing with Temperature and Concentration?

• What is a catalyst ?

• What was the catalyst used in the decomposition of hydrogen peroxide ?

• Name 3 other factors that affect the rate of reaction.

This now concludes our Presentation

By: Adrian, Emma, Fraser and Roderick