Practical Examination - Chemistry Lab

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Questions and Answers

What type of flame is optimal for general heating and why?

A non-luminous oxidizing flame is optimal because it provides maximum heat due to complete combustion of hydrocarbons.

Why is it important to rotate a glass tube while heating it?

Rotating the tube ensures uniform heating from all sides, preventing folds at the bend.

Define crystallization and its purpose.

Crystallization is the conversion of a substance into a well-defined geometric shape, done to prepare a substance in the state of highest purity.

What is solubility, and how is it measured?

Solubility is the amount of solute that can dissolve in 100g of solvent to create a saturated solution. Signup and view all the answers

Explain the term 'water of crystallization'.

Water of crystallization refers to the definite number of water molecules associated with one formula unit of a compound. Signup and view all the answers

What is a saturated solution?

A saturated solution is one in which no more solute can be dissolved at a specific temperature. Signup and view all the answers

Why is it not advisable to heat a solution to dryness when obtaining crystals?

Heating to dryness does not remove soluble impurities, resulting in poor quality crystals. Signup and view all the answers

What does the pH of a solution signify?

The pH signifies the concentration of hydronium ions in moles per liter, defined as pH = -log[H3O+]. Signup and view all the answers

What is the purpose of using a universal indicator in determining pH values?

To visually indicate the acidity or basicity of different samples through color changes. Signup and view all the answers

List two preliminary tests that can be performed on a simple inorganic salt.

Flame test and solubility test. Signup and view all the answers

What is the significance of obtaining concordant burette readings (CBR) in titration?

Concordant burette readings ensure accuracy and reliability in measuring the volume of titrant used. Signup and view all the answers

Explain one method for confirming the presence of an acid radical in an inorganic salt.

Performing a specific reaction test that yields a characteristic result, such as effervescence for carbonate radicals. Signup and view all the answers

How can the concentration of NaOH be determined using 0.1M oxalic acid in volumetric analysis?

By performing a titration and applying the formula that relates moles of acid to moles of base. Signup and view all the answers

What role do air holes play in a Bunsen burner?

They regulate the supply of air to provide a hotter and cleaner flame. Signup and view all the answers

What is the importance of having a certified record during the lab exam?

It verifies that the student has completed prior practical work accurately and responsibly. Signup and view all the answers

Why must students follow the order of tests in salt analysis?

To prevent inaccuracies in identifying acid radicals due to potential interference from other components. Signup and view all the answers

Study Notes

Practical Examination - Instructions

Students must submit a neatly wrapped certified lab record.
Record concordant burette readings (CBR) in the column provided.
Provide two correct confirmations for acid radicals.
If a confirmation is incorrect, marks will be given in another test.
Follow the examination instructions and the order of the tests to avoid inaccurate acid radical reports.

Viva Questions

Question 1: Why does a Bunsen burner have air holes?
- Answer: To control the air supply.
Question 2: What flame type is best for general heating?
- Answer: Non-luminous oxidizing flame, due to complete hydrocarbon combustion.
Question 3: Why use a broad flame to bend glass tubing?
- Answer: Narrow flames cause bends in the tube.
Question 4: Why rotate the glass tube during heating?
- Answer: Ensuring uniform heating from all sides.
Question 5: Define crystallisation. Why is it done?
- Answer: Changing a substance into a well-defined geometrical shape. Crystallisation produces a highly pure substance.

Additional Chemistry Concepts

Solubility: The amount of solute that dissolves in 100g of solvent to form a saturated solution.
Water of crystallisation: The fixed number of water molecules within a compound.
Saturated solution: A solution where no more solute can dissolve at a given temperature.
Why not heat to dryness to obtain crystals?:
- Heating to dryness doesn't remove impurities, leading to crystals of poor quality.
Characteristics of crystals: Well-defined geometry and shape.
pH Definition: Negative logarithm of hydronium ion concentration (moles/litre). pH = -log[H₃O⁺].
Effect of Dilution on pH:
- Acidic solution: pH increases with dilution
- Basic solution: pH decreases with dilution
Law of Mass Action: Reaction rate is proportional to the reacting substances' concentrations.
Chemical Equilibrium: When the forward and backward reaction rates are equal, the net change is zero.
Effect of Temperature on Equilibrium: Increasing temperature favors the endothermic reaction.

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Description

This quiz covers essential instructions and viva questions related to the practical examination in chemistry. Topics include lab record preparation, equipment usage, and important concepts like crystallization and flame types. Students will need to demonstrate understanding of practical lab techniques and safety protocols.