Community College of Philadelphia

Department of Chemistry

Laboratory Report Sheet
Name:

Date:

Email:

Laboratory Instructor:

Course Nbr.: CHEM 101 Distance

Section:

Experiment Nbr.: 5

Experiment Title: REACTIONS

Purpose:

Concepts (textbook):

Conclusion:

LAB 5 – REACTIONS
A mixture of chemicals may interact to produce different chemicals. If so, this is referred to as a chemical reaction and it can be represented by a balanced chemical equation. Most reactions are also accompanied by a change in energy, either releasing chemical energy as heat into the surroundings (an exothermic reaction) or absorbing heat from the surroundings that is stored in the chemical bonds (an endothermic reaction). Some reactions go faster, if the reaction is catalyzed.

Refer to your textbook for further background on signs of reactions, catalysts, heat/energy changes that accompany reactions, types of reactions and balancing equations.

In this experiment, you will perform several simple experiments to determine: if a change is exothermic or endothermic, to see the effect on a reaction’s rate when a catalyst is present and to observe the changes which accompany reactions. You will then practice balancing the equations for these reactions.

Needed: White vinegar (which is 5% acetic acid in water)

Baking soda (NaHCO3) Hydrogen Peroxide (H2O2)

A piece of tarnished silverware A slice of fresh potato

Measuring spoons Several glasses
A rubberband A large pan (metal or glass)

Procedure:

I Determination of Energy Change Accompanying a Reaction

Take a rubber band and hold it gently against your upper lip.

Quickly stretch it to its limit. Does your lip feel warm or cool? (1)

Is this reaction/stretching an endothermic or exothermic process? (2). Explain your reasoning. (3)

II Reaction of NaHCO3 and HC2H3O2

1. Record your initial observations on the vinegar (acetic acid) solution (4).

2. Measure out ½ teaspoon (5) of baking soda into a glass. Record your observations (i.e., color, physical state, odor, etc.) on this solid (6a). Add 1 Tablespoon of warm water to the solid and stir. Does it dissolve? (6b)

3. Add one tablespoonful at a time of vinegar to the NaHCO3 with stirring until the reaction is complete. Record the amount of acetic acid solution used (7) and your observations on the reaction (8 a&b).

4. Gently warm the remaining solution in an oven or microwave until all the water has evaporated. Record your observations (9b) on the remaining solid. Measure (as well as possible) the amount of solid sodium acetate (NaC2H3O2) produced using your measuring spoons (9a).

Balanced Equations for this reaction:

HC2H3O2(aq) + NaHCO3(s) CO2(g) + H2O(?) + NaC2H3O2(aq)

heat

H2O(?) + NaC2H3O2(aq) H2O(g) + NaC2H3O2(s)

III Reaction of H2O2

1. Pour about ½ cup of hydrogen peroxide (H2O2) into a glass.

2. Is its decomposition reaction observable? (10)

3. Add a slice of potato to the solution. Is the decomposition reaction observable now?(11)

4. Record your observations (12). What is the function of the potato? (13)

5. What type of reaction is this (synthesis, decomposition, single replacement or double replacement)? (14)

Balanced Equations for this reaction:

2 H2O2 (aq) 2 H2O (?) + O2 (g) (uncatalyzed)

2 H2O2 (aq) potato enzyme 2 H2O (?) + O2 (g) (catalyzed)

IV Reaction of Ag2S and Al

1. Take a large pan and place enough water (1 to 2 liters or quarts) in it to cover the tarnished piece of metal that you will immerse.

2. Add 8 tablespoons of baking soda. Warm the solution but do not boil it.

3. Place a piece of Al foil on the bottom of the pan. Then add the tarnished silverware, reheat the water almost to boiling and observe after letting sit overnight (after 8 to10 hours) (15). Remove the silverware and rinse in running water; scrub gently with a brillo-type pad.

4. What type of reaction is this (synthesis, decomposition, single replacement or double replacement)? (16)

Balanced Equation for this reaction:

3 Ag2S (s) + 2 Al (s) NaHCO3 6 Ag (s) + Al2S3 (aq)
REPORT SHEET: LAB 5 – Reactions
I Determination of Energy Change Accompanying a Reaction

(1) Did your lip feel warm or cool? _____________________

(2) Was the process endothermic or exothermic?________________

(3) Explain your reasoning.

II Reaction of NaHCO3 and HC2H3O2
(4) Observations on Acetic Acid (vinegar) solution

(5) Amount of NaHCO3 used _______________________ teaspoons

(6a) Observations on Sodium Bicarbonate

(6b) Is sodium bicarbonate water-soluble? ______________

(7) Total amount of HC2H3O2 solution used __________________ tablespoons

(8a) Observations [How was the CO2 gas production observed?]

(8b) How did you determine when the reaction was complete?

(Give at least 2 indications).

(9a). Amount of NaC2H3O2 solid produced _____________________________

(9b) Observations on Sodium Acetate:

III Reaction of H2O2

(10) Is the decomposition reaction observable? Yes or no? ____________

(11) Is the decomposition reaction with potato observable? Yes or no? ____________

(12) Observations (sign of a reaction occurring):

(13) What is the function of the potato? Potato is __________________________

(14) Type (classification) of reaction ______________________________

IV Reaction of Ag2S and Al
(15) Observations on metal
(16) What type of reaction is this (synthesis, decomposition, single replacement or double replacement)? Type (classification) of reaction ____________________

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