# LAB 3 Stoichiometry And Chemical Reactions

Topics: Chemical reaction, Chemistry, Mole Pages: 9 (1078 words) Published: April 14, 2015
Practicum 2: Stoichiometry of Chemical Reactions

Written by:
Ade Istianto (2014990003)
Aprizky Bagus Heldinto (2014990002)
Deas Pratama (2014360004)
Paskah Andreas Deo Gratias (2014370005)

Sampoerna University

ABSTRACT

This experiment is endure to determine and study about the stoichiometry of chemical reactions in certain chemicals. The experiments were to make sure student are able to use and learn the Job’s method-the method of continuous variation-for determine the reaction stoichiometry. In the method of continuous variations, the total number of moles of reactants is kept constant for a series of measurements. Each measurement is made with a different mole ratio or mole fraction of reactants. The maximum change will occur when the mole ratio of the reactants is closest to the optimum ratio which is the stoichiometric ratio in the chemical equation. A job plot itself is used to determine the stoichiometry of binding event. This method is widely used in analytical chemistry, instrumental analysis, and advanced chemical equilibrium. In solutions that used in the experiment were two species are present reaction between CuSO4 and NaOH. In this method of experiment, the total molar concentration of the two solutions are held constant, but their mole fractions are varied. In the second experiment, it was observed the reaction of acid-base in solution of NaOH with HCl in different condition of volume for each. An observable that is proportional to complex information is plotted against the mole fractions of these two components. The maximum on the plot correspond to stoichiometry of the solutions or species if sufficiently high concentrations are used.

CHAPTER I
OBJECTIVES

Objectives:

1. To learn the Job’s method (the method of continuous variation). 2. To be able to determine the reaction stoichiometry.

CHAPTER II
METHODOLOGY

2.1 Apparatus
Materials:
Chemicals

Equipment

HCl 1M

Test tube

NaOH 1M

Beaker Glass

NaOH 2M

Graduated Cylinders

CuSO4 1M

Spatula
Glass Rods
Thermometer

2.2 Procedure
Reaction of CuSO4 and NaOH:
1. Place 40 mL of aqueous NaOH 2M in the 100 mL beaker glass and measure the temperature.

2. Place 10 mL of aqueous CuSO4 1M in the 50 mL beaker glass and measure the temperature.
3. Add the aqueous CuSO4 1M into the aqueous NaOH 2M, stir it with glass rod and measure the temperature of the solution.
4. Repeat 1-3 steps with the following composition.
Volume of NaOH

Volume of CuSO4

(mL)

(mL)

1

30

20

2

20

30

3

10

40

Condition

5. Plot graph of the NaOH volume versus temperature, in which temperature of mixed solution and

=

,

=

= initial temperature of each solution.

Acid-base reaction
1. Place 5 mL of aqueous NaOH 1M in the 50 mL beaker glass and measure the temperature.
2. Place 25 mL of aqueous HCl 1M in the 50 mL beaker glass and measure the temperature.
3. Add aqueous NaOH 1M into the aqueous HCl 1M, stir it with glass rod and measure the temperature of the solution.
4. Repeat 1-3 steps with the following composition.

Volume of NaOH

Volume of HCl

(mL)

(mL)

1

10

20

2

15

15

3

20

10

4

25

5

5

30

-

6

-

30

Condition

5. Plot graph of the NaOH or HCl volume versus temperature, in which = temperature of mixed solution and

=

= initial temperature of each solution.

6. Do the same experiment for NaOH 1M and H2SO4 1M

,

CHAPTER III
RESULT AND DISCUSSION

3.1 The Determination of Job’s Method.
Job’s method or the method of continuous variation is used to determine the stoichiometry of a reaction. In this method, the total molar concentration of the two reactants is held constant, but their mole fractions are varied. An observable that is proportional to the products formation (such as change of temperature, amount of products, pH solution, and color of solution) is plotted against the mole...

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