Pre Lab Module EC015

EC015
Pre-Lab Module

EXPERIMENT 1
DETERMINATION OF THE FORMULA UNIT OF A COMPOUND

Course Learning Outcome:

Solve chemistry related problems by applying basic concepts and principles in physical
chemistry. (C4, PLO4, CTPS3, MQF LO6)

Learning Outcomes:

At the end of this lesson, students should be able to:
i. Define the terms compound, formula unit, empirical formula and molecular formula
ii. Determine the formula unit of a compound

iii. Identify the safety precautions of the experiment

Student Learning Time:

Face-to-face Non face-to-face
1 hour 1 hour

Direction: Read over the lab manual and then answer the following question.

Introduction:
1. Define the term compound.

2. What is a formula unit of a compound?

3. State the difference between empirical formula and molecular formula.

4. The formula unit of a compound can be determined if the composition or the ratio of the
elements in the compound is known. Consider a compound that contains 0.20 mole of
aluminum and 0.30 mole of oxygen. Determine its formula unit.

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EC015
Pre-Lab Module

Procedure:
1. List the safety cautions in this experiment.

2. The compound should not be heated to the point that it melts. Explain.
3. Why is the compound reheated, cooled and reweighed after the first heating?
4. Construct a table to record the data for the experiment.

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EC015
Pre-Lab Module

Experiment 1 : Data Analysis

An experiment was conducted to determine the formula unit of magnesium oxide.
The following data was recorded.

Mass of empty crucible + lid = 24.0037 g
Mass of crucible + lid + magnesium strip = 24.3046 g
Mass of crucible + lid + magnesium oxide:
a) after first heating = 24.5278 g
b) after second heating = 24.5097 g

Determine the formula unit of the compound.

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EC015
Pre-Lab Module

EXPERIMENT 2
ACID-BASE TITRATION - DETERMINATION OF THE CONCENTRATION

OF HYDROCHLORIC ACID SOLUTION

Course Learning Outcome:

Solve chemistry related problems by applying basic concepts and principles in physical
chemistry. (C4, PLO4, CTPS3, MQF LO6)

Learning Outcomes:

At the end of this lesson, students will be able:
i. To define molarity and standard solution
ii. To state the use of standard solution

iii. To describe the preparation of a standard solution of oxalic acid
iv. To differentiate between end point and equivalnce point.
v. To explain the precautions required during titration
vi. To calculate the concentration of HCl solution in an acid-base titration

Student-Learning Time:

Face-to-face Non face-to-face
1 hour 1 hour

Direction: Read over the lab manual and then answer the following question.

Introduction
1. Define molarity.

2. What is a standard solution? State the use of a standard solution.

3. What is the difference between end point and equivalence point?

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EC015
Pre-Lab Module

Procedure
1. State three precautions that must be taken during titration to ensure the accuracy of

results. State a reason for each precaution.

2. Briefly describe how to prepare 250 mL standard solution of hydrated oxalic acid
(C2H2O4.2H2O) with a concentration of 0.25 M.

3. How to determine the end point of the titration?

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EC015
Pre-Lab Module

Experiment 2 : Data Analysis

A titration of 25.00 mL of an x M HCl solution with 0.15 M NaOH starts at a burette reading
for NaOH of 0.20 mL. The burette reading of the end point is 24.10 mL.

i. What was the volume of NaOH dispensed?
ii. Calculate the number of moles of NaOH dispensed.
iii. Write the balanced equation for the neutralisation reaction.
iv. Calculate the number of moles of HCl present in the acid solution.
v. Determine the value of x.

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EC015
Pre-Lab Module

EXPERIMENT 3
DETERMINATION OF THE MOLAR MASS OF A METAL

Course Learning Outcome:

Solve chemistry related problems by applying basic concepts and principles in physical
chemistry. (C4, PLO4, CTPS3, MQF LO6)

Learning Outcomes:

At the end of this lesson, students will be able:
i. To determine the molar mass of an alkaline earth metal by back-titration method.

Student-Learning Time:

Face-to-face Non face-to-face
1 hour 1 hour

Direction: Read over the lab manual and then answer the following question.

Introduction:

1. What is back-titration?

2. Give one example of alkaline earth metal and write the equation for the reaction between
the metal and HCl.

Procedure:
Explain briefly how to determine the molar mass of an unknown metal by using back-
titration method.

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EC015
Pre-Lab Module

Experiment 3 : Data Analysis

A 0.2730 g sample of unknown metal, Y with oxidation number of +2, was completely
reacted with 25.00 mL of 0.50 M excess HCl. The remaining solution required 4.15 mL of
1.00 M NaOH to reach end point. Calculate the,

i. number of mole of HCl reacted with NaOH.
ii. number of mole of HCl reacted with Y.
iii. number of mole of Y metal reacted.
iv. molar mass of Y.

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EC015
Pre-Lab Module

EXPERIMENT 4
CHARLES’ LAW AND THE IDEAL GAS LAW

Course Learning Outcome:

Solve chemistry related problems by applying basic concepts and principles in physical
chemistry. (C4, PLO4, CTPS3, MQF LO6)

Learning Outcomes:

At the end of this lesson, students will be able to:
i. verify Charles’ Law by using graphical method.
ii. determine the molar mass of a volatile liquid.

Student-Learning Time:

Face-to-face Non face-to-face
1 hour 1 hour

Direction: Read over the lab manual and then answer the following question.

Introduction
(A) Verify Charles’ Law.
1. Define Charles’ Law.

2. Based on kinetic molecular theory, describe how the volume of gas changes when the
temperature increases.

3. What variables are held constant in Charles’ Law?

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Pre-Lab Module

(B) Determination of the molar mass of a volatile liquid.
1. State the ideal gas equation.

2. Derive the formula that relates the mass and the molar mass by using the ideal gas
equation.

3. What is the unit of molar mass?

Procedure
(A) Verify Charles’ Law.
Why should we use the same Charles’ law apparatus at all four different temperature?

(B) Determination of the molar mass of a volatile liquid.
1. Why do you need to prick a tiny hole in the middle of the aluminium foil?

2. When does the temperature of the water in beaker have to be recorded?

3. Why the conical flask is filled with water up to the brim?

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Pre-Lab Module

Experiment 4 : Data Analysis
V

0 T (oC)

1. Mark the absolute zero temperature in the graph above. What is the volume of the gas at
this temperature?

2. Based on the graph, state the relationship between volume of the gas, V and absolute
temperature, T(K).

3. A 0.30 g of gas Y at 3.00 atm occupies 82.0 mL flask. Calculate the molar mass of gas Y
if temperature of the gas is 27.0oC.

4. State the possible errors in the experiment.

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EC015
Pre-Lab Module

EXPERIMENT 5
CHEMICAL EQUILIBRIUM

Course Learning Outcome:

Solve chemistry related problems by applying basic concepts and principles in physical
chemistry. (C4, PLO4, CTPS3, MQF LO6)

Learning Outcomes:

At the end of this lesson, students will be able to:
i. study the effect of concentration and temperature on chemical equilibrium.
ii. determine the equilibrium constant, Kc of a reaction

Student-Learning Time:

Face-to-face Non face-to-face
1 hour 1 hour

Direction: Read over the lab manual and then answer the following question.

Introduction
1. What is meant by reversible reaction?

2. State two characteristics of dynamic equilibrium.
3. State Le Chatelier’s Principle.

4. State the factors that influence the chemical equilibrium.

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5. Given the equation which is in equilibrium: EC015
Pre-Lab Module
N2(g) + 3H2(g) 2NH3(g)
∆H = -92.83 kJ

Predict the direction of equilibrium if :

i. nitrogen gas is added

ii. gas is removed

iii. temperature of the system is increased.

6. Given the equation in equilibrium:

SbCl3(aq) + H2O(l) SbOCl(s) + 2HCl(aq)

i. Write the Kc expression for the above system

ii. Explain why H2O(l) and SbOCl(s) are not included in Kc expression.

Procedure
1. State the precautions for these experiments.

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EC015
Pre-Lab Module

Experiment 5 : Data Analysis

(A) The effect of concentration in the formation of thiocyanoiron (III) complex ion

1. Given the equation [ Fe(SCN)2]+(aq)
(blood-red)
Fe3+(aq) + 2 SCN-(aq)
(yellowish brown)

When the system is at equilibrium, a blood-red solution is observed. The colour
intensity of the solution is reduced by adding distilled water.

a) If Fe(NO3)3 is added to the above system,
i. what is the disturbance applied to the reaction?

ii. predict the observation.

iii. explain the effect of the above disturbance to the equilibrium position.

b) When NaOH is added, the colour of the solution changes to yellowish brown.

i. State the change in equilibrium position.
ii. Write an equation between Fe3+ and NaOH.
iii. What is the effect on the concentration of Fe3+?

(B) The effect of temperature

2. Consider the following equilibrium system,

A(aq) + B(aq) C(aq)
(yellow) (blue)

i. A green solution is observed indicating a mixture of yellow and blue at room
temperature. What can be deduced from the observation?

ii. The above solution turns yellow in the hot water bath. Explain.

iii. State the colour of solution after it is placed in the ice bath. Explain.

iv. Predict the forward reaction as exothermic or endothermic.

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EC015
Pre-Lab Module

EXPERIMENT 6
pH MEASUREMENT AND ITS APPLICATIONS

Course Learning Outcome:

Solve chemistry related problems by applying basic concepts and principles in physical
chemistry. (C4, PLO4, CTPS3, MQF LO6)

Learning Outcomes:

At the end of this lesson, students will be able to:
i. Perform calculations involving pH, dissociation constant, Ka and initial concentration.

Student-Learning Time:

Face-to-face Non face-to-face
1 hour 1 hour

Direction: Read over the lab manual and then answer the following question.

Introduction:
1. Define pH.

2. Give two methods to determine pH in the laboratory.

3. Explain the differences between strong acid and weak acid.

4. What is a buffer solution ?

5. Write the expression of Ka for a weak acid, HA. 15

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EC015
Pre-Lab Module

Procedure:
1. Suggest suitable indicators for titration between

i. Nitric acid, HNO3 and potassium hydroxide, KOH

ii. Nitric acid, HNO3 and ammonia, NH3

iii. Sodium hydroxide, NaOH and hydrocyanic acid, HCN

2. State the composition of an acidic buffer solution.

3. Classify the following salt as acidic, basic or neutral salt.

Salt Type
I. NaCl
II. CH3COONa
III. NH4NO3

4. List down all precautions of the experiment.

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Pre-Lab Module

Experiment 6 : Data Analysis

1. Calculate the percentage of ionisation of 0.1 M and 1.0 M acetic acid with pH 2.87 and
2.37 respectively.

2. How does the percentage of ionisation change with its concentration?

3. Refer to the pH values of acetic acid in Question 1, calculate their dissociation constant,
Ka.

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