North Seattle College Chemistry 121

Lab 4: Factor Affecting Rate of Reaction

Objectives:

-  To observe changes in physical and chemical properties during a variety of chemical reactions

-  To write balanced chemical equations for all reactions carried out

-  To study the factor affecting the rates of reactions

Background:

A chemical reaction consists of reactants and products. The reactants are what you start with (also called starting materials) and the products are the new compounds that form during the reaction. Several factors affect the rate at which reactions occur. In this lab, you will be performing six groups of reactions to determine the effect of each of the following on the reaction rate: nature of reactants, concentration of reactants, surface area, temperature and catalyst. The solutions in this lab are described by their concentration in units of Molarity (M), which is equal to number of moles of dissolved substance per liter of solution.

Pre-Lab: (To be submitted at the beginning of lab on a separate sheet of paper)

1.  Write the chemical formula for each type of acid used in Part 1.

2.  Which concentration of sulfuric acid do you expect to react most vigorously with Mg in Part 3?

3.  Rate is quantitative with the units of M/sec. We are not measuring anything quantitative for this lab. How will you study the rate for this lab?

Safety Notes:

·  Wear your safety goggles at all times.

·  Handle all chemicals carefully (rinse them off your skin immediately).

·  Take only the amount of chemicals that you need and never put unused chemicals back into the reagent bottle.

·  Discard all used or leftover chemicals in the waste containers provided (do not pour any chemicals down the sink and do not put your rinse water in the waste).

·  Clean up any spills immediately and clean up everything when finished.

Procedures:

Carry out the following reactions. For each reaction, carefully write down all observations. Use a clean test tube for each reaction.

Part 1. Nature of Reactants 1

1.  Obtain 5 test tubes, number them, and place a 1 cm strip of Mg in each.

2.  Add 1 mL of the following acids to the test tubes as described below and note the rates:

Test tube / Observations
#1 / 2M sulfuric acid
#2 / 2M hydrochloric acid
#3 / 2M nitric acid
#4 / 2M phosphoric acid
#5 / 2M acetic acid

Part 2. Nature of Reactants 2

1.  Obtain 3 test tubes, number them, and place 1 mL of 6.0M HCl in each.

2.  Add a 1 cm polished strip of the following metals to the test tubes as described below and note the rates:

Test tube / Observations
#1 / Mg
#2 / Zn
#3 / Cu

Part 3. Concentration of Reactants

1.  Obtain 3 test tubes, number them, and place a 1 cm strip of Mg in each.

2.  Add 1 mL of the following acids to the test tubes as described below and note the rates:

Test tube / Observations
#1 / 1M sulfuric acid
#2 / 3M sulfuric acid
#3 / 6M sulfuric acid

Part 4. Surface Area

1.  Obtain 2 large test tubes and number them

2.  Place one marble chip (CaCO3) into one test tube and about the same amount of crushed marble chips into the other test tube.

3.  Add 1 mL of 6.0M HCl into each test tube and note the rates:

Test tube / Observations

Part 5. Temperature

1.  Obtain 3 test tubes and add 1 mL of 6.0M HCl to each.

2.  Place one test tube in an ice bath, the second in a warm water bath, and the third in a tap water bath.

3.  Wait 5 minutes.

4.  Add a piece of Zn to each test tube and note the rates:

Test tube / Observations

Part 6. Catalyst

1.  Obtain 2 test tubes and add 1 mL of 3% H2O2 to each.

2.  Add a few grains of MnO2 to one of the test tubes and note the rates:

Test tube / Observations

Post Lab: (what you should turn in)

·  Your data tables

·  The answers to the post-lab questions (below), written very legibly.

1.  Write a balanced reaction for each of the following (including states):

Part 1. Magnesium and acetic acid

Part 2. Magnesium and hydrochloric acid

Part 3. Magnesium and sulfuric acid

Part 4. Calcium carbonate and hydrochloric acid

(Hint: there are 3 products and the gas formed here is CO2, not H2!)

Part 5. Zinc and hydrochloric acid

Part 6. decomposition of hydrogen peroxide (Hint: one product is water)

2.  What would happen to the rate in part 1, if you use the same amount of Mg but in the form of a fine powder instead of a ribbon or chunks? Why?

3.  In Part 1, which reactions were the fastest? How could you tell?

4.  For Parts 2-6, list the reactions in increasing rate.

For example, for part 2:

Mg + HCl < Cu + HCl < Zn + HCl

(Reaction with Mg being the slowest, reaction with Zn being the fastest)

Part 2. ______< ______< ______

Part 3. ______< ______< ______

Part 4. ______< ______

Part 5. ______< ______< ______

Part 6. ______< ______

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