Thursday, June 5, 2025

HS 2nd year Chemistry Unit 2: Electrochemistry

 

🔹 Topic: Electrochemical Cells

Q1. What is an electrochemical cell?
Answer:
An electrochemical cell is a device that converts chemical energy into electrical energy through a redox reaction.

Keywords with Bengali Meaning:

  • Electrochemical cell – ইলেক্ট্রোকেমিক্যাল কোষ

  • Chemical energy – রাসায়নিক শক্তি

  • Electrical energy – বৈদ্যুতিক শক্তি

  • Redox reaction – রিডক্স বিক্রিয়া

🔹 Topic: Galvanic Cells (Voltaic Cells)

Q2. What is a galvanic cell? Give an example.
Answer:
A galvanic cell is an electrochemical cell in which a spontaneous redox reaction produces electrical energy. Example: Daniell Cell.

Keywords with Bengali Meaning:

  • Galvanic cell – গ্যালভানিক কোষ

  • Spontaneous reaction – স্বতঃস্ফূর্ত বিক্রিয়া

  • Daniell Cell – ড্যানিয়েল কোষ

Q3. What is a salt bridge and what is its function?
Answer:
A salt bridge is a U-shaped tube containing a gel permeated with an inert electrolyte. It maintains electrical neutrality in the cell by allowing the flow of ions.

Keywords:

  • Salt bridge – লবণ সেতু

  • Inert electrolyte – নিষ্ক্রিয় ইলেক্ট্রোলাইট

  • Electrical neutrality – বৈদ্যুতিক নিরপেক্ষতা

🔹 Topic: Electrode Potential

Q4. What is standard electrode potential?
Answer:
Standard electrode potential is the potential of a half-cell under standard conditions (1 M concentration, 1 atm pressure, 25°C) when connected to a standard hydrogen electrode.

Keywords:

  • Electrode potential – ইলেক্ট্রোড পটেনশিয়াল

  • Standard conditions – মানক অবস্থা

🔹 Topic: Nernst Equation

Q5. State the Nernst Equation and its significance.
Answer:
The Nernst equation is:
Ecell=Ecello−0.0591nlog⁡QE_{cell} = E^o_{cell} - \frac{0.0591}{n} \log Q
It relates the cell potential to the standard electrode potential and the concentration of the ions involved.

Keywords:

  • Nernst Equation – নের্নস্ট সমীকরণ

  • Cell potential – কোষের বিভব

  • Concentration – ঘনত্ব

🔹 Topic: Conductance of Electrolytic Solutions

Q6. Define conductivity and molar conductivity.
Answer:

  • Conductivity (κ) is the conductance of a solution per unit length and area.

  • Molar conductivity (Λm) is the conductivity of an electrolytic solution divided by its concentration.

Keywords:

  • Conductivity – পরিবাহিতা

  • Molar conductivity – মোলার পরিবাহিতা

  • Electrolyte – ইলেক্ট্রোলাইট

Q7. What is the effect of dilution on conductivity and molar conductivity?
Answer:
On dilution, conductivity decreases but molar conductivity increases, especially for weak electrolytes due to increased ionization.

Keywords:

  • Dilution – পাতলা করা

  • Ionization – আয়নায়ন

🔹 Topic: Electrolytic Cells and Electrolysis

Q8. What is electrolysis?
Answer:
Electrolysis is the process of bringing about a chemical change using electricity in an electrolytic cell.

Keywords:

  • Electrolysis – ইলেক্ট্রোলাইসিস

  • Electrolytic cell – ইলেক্ট্রোলাইটিক কোষ

Q9. State Faraday’s laws of electrolysis.
Answer:

  1. The mass of substance liberated at an electrode is proportional to the quantity of electricity passed.

  2. The masses of different substances liberated by the same quantity of electricity are proportional to their equivalent weights.

Keywords:

  • Faraday’s laws – ফ্যারাডের সূত্র

  • Equivalent weight – সমতুল্য ওজন

  • Quantity of electricity – বিদ্যুতের পরিমাণ


📘 Worksheet: Chapter 2 – Electrochemistry

Subject: Chemistry | Class: 12 | Chapter: Electrochemistry
Instructions: Answer the following questions in the space provided. Meanings of important keywords are also given for your reference.

1. Define an electrochemical cell.

🔑 Keywords:

  • Electrochemical cell – ইলেক্ট্রোকেমিক্যাল কোষ

  • Chemical energy – রাসায়নিক শক্তি

  • Electrical energy – বৈদ্যুতিক শক্তি

  • Redox reaction – রিডক্স বিক্রিয়া

Answer:

2. What is a galvanic cell? Give one example.

🔑 Keywords:

  • Galvanic cell – গ্যালভানিক কোষ

  • Spontaneous reaction – স্বতঃস্ফূর্ত বিক্রিয়া

  • Daniell Cell – ড্যানিয়েল কোষ

Answer:

3. What is a salt bridge and what is its function?

🔑 Keywords:

  • Salt bridge – লবণ সেতু

  • Inert electrolyte – নিষ্ক্রিয় ইলেক্ট্রোলাইট

  • Electrical neutrality – বৈদ্যুতিক নিরপেক্ষতা

Answer:

4. Define standard electrode potential.

🔑 Keywords:

  • Electrode potential – ইলেক্ট্রোড পটেনশিয়াল

  • Standard conditions – মানক অবস্থা

Answer:

5. Write the Nernst Equation. What does it tell us?

🔑 Keywords:

  • Nernst Equation – নের্নস্ট সমীকরণ

  • Cell potential – কোষের বিভব

  • Concentration – ঘনত্ব

Answer:

6. Define conductivity and molar conductivity.

🔑 Keywords:

  • Conductivity – পরিবাহিতা

  • Molar conductivity – মোলার পরিবাহিতা

  • Electrolyte – ইলেক্ট্রোলাইট

Answer:

7. What is the effect of dilution on conductivity and molar conductivity?

🔑 Keywords:

  • Dilution – পাতলা করা

  • Ionization – আয়নায়ন

Answer:

8. What is electrolysis?

🔑 Keywords:

  • Electrolysis – ইলেক্ট্রোলাইসিস

  • Electrolytic cell – ইলেক্ট্রোলাইটিক কোষ

Answer:

9. State Faraday’s laws of electrolysis.

🔑 Keywords:

  • Faraday’s laws – ফ্যারাডের সূত্র

  • Equivalent weight – সমতুল্য ওজন

  • Quantity of electricity – বিদ্যুতের পরিমাণ

Answer:


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HS 2nd year Chemistry Unit 1: Solutions

 

🔹 Topic 1.1: Types of Solutions

Q1. What is a solution? Explain types of solutions with examples.
Ans: A solution is a homogeneous mixture of two or more components. The component in larger quantity is called the solvent, and the one in lesser quantity is the solute. Types of solutions include:

  • Gas in gas (e.g., air)

  • Liquid in liquid (e.g., ethanol in water)

  • Solid in liquid (e.g., salt in water)

  • Gas in liquid (e.g., oxygen in water)

Keywords:

  • Solution = দ্রবণ

  • Homogeneous = সজাতীয়

  • Solvent = দ্রাবক

  • Solute = দ্রব্য

🔹 Topic 1.2: Expressing Concentration of Solutions

Q2. Write five methods to express the concentration of solutions.
Ans:

  1. Mass % (w/w) = (Mass of solute / Mass of solution) × 100

  2. Volume % (v/v) = (Volume of solute / Volume of solution) × 100

  3. Mass by volume % (w/v) = (Mass of solute / Volume of solution in mL) × 100

  4. Parts per million (ppm) = (Mass of component / Total mass) × 10⁶

  5. Mole fraction (x) = Moles of component / Total moles

  6. Molarity (M) = Moles of solute / Volume of solution in L

  7. Molality (m) = Moles of solute / Mass of solvent in kg

Keywords:

  • Concentration = ঘনত্ব

  • Mass = ভর

  • Volume = আয়তন

  • Mole = মোল

  • Fraction = ভগ্নাংশ

🔹 Topic 1.3: Solubility

Q3. What is solubility? How does temperature and pressure affect it?
Ans:
Solubility is the maximum amount of solute that can dissolve in a solvent at a particular temperature and pressure.

  • Effect of temperature: Solubility of solids increases if dissolution is endothermic.

  • Effect of pressure: Little effect on solids, but for gases, solubility increases with pressure.

Keywords:

  • Solubility = দ্রাব্যতা

  • Temperature = তাপমাত্রা

  • Pressure = চাপ

  • Endothermic = উষ্ণগ্রাহী

  • Exothermic = তাপ নির্গতকারী

🔹 Topic 1.3.2: Henry’s Law

Q4. State Henry’s Law and give its application.
Ans:
Henry’s Law: The solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid.
p = KH × x (KH = Henry’s constant)
Applications:

  • Bottling of soft drinks

  • Scuba diving

  • Breathing at high altitudes

Keywords:

  • Partial pressure = আংশিক চাপ

  • Constant = ধ্রুবক

  • Solubility = দ্রাব্যতা

🔹 Topic 1.4: Vapour Pressure of Liquid Solutions

Q5. State Raoult’s Law.
Ans:
Raoult’s Law: The partial vapour pressure of each volatile component of a solution is proportional to its mole fraction.
p₁ = x₁p₁⁰ and p₂ = x₂p₂⁰

Keywords:

  • Vapour pressure = বাষ্পচাপ

  • Mole fraction = মোল ভগ্নাংশ

🔹 Topic 1.5: Ideal and Non-Ideal Solutions

Q6. Distinguish between ideal and non-ideal solutions.
Ans:

  • Ideal solution obeys Raoult’s law at all compositions. ΔHmix = 0 and ΔVmix = 0

  • Non-ideal solution shows deviation from Raoult’s law.

    • Positive deviation: Weak A-B interactions

    • Negative deviation: Strong A-B interactions

Keywords:

  • Ideal = আদর্শ

  • Deviation = বিচ্যুতি

  • Interaction = পারস্পরিক ক্রিয়া

🔹 Topic 1.6: Colligative Properties

Q7. What are colligative properties? List them.
Ans:
Colligative properties are properties that depend only on the number of solute particles in a solution, not on their nature.
They include:

  1. Relative lowering of vapour pressure

  2. Elevation of boiling point

  3. Depression of freezing point

  4. Osmotic pressure

Keywords:

  • Colligative = সম্মিলিত

  • Boiling point = স্ফুটনাঙ্ক

  • Freezing point = হিমাঙ্ক

  • Osmosis = অভিস্রবণ

🔹 Topic 1.7: Abnormal Molar Mass and van’t Hoff Factor

Q8. What is van’t Hoff factor? What is its significance?
Ans:
Van’t Hoff factor (i) accounts for the degree of association or dissociation of solutes in a solution.

  • i = observed colligative property / calculated colligative property

  • i > 1 for dissociation, i < 1 for association

Keywords:

  • Association = যুক্তি

  • Dissociation = বিযুক্তি

  • Factor = গুণনীয়ক


🧪 Worksheet: Chapter 1 – Solutions

🔹 Section A: Short Answer Questions (2 marks each)

  1. Define a binary solution.

  2. What is the difference between solute and solvent?

  3. Write the formula for mole fraction.

  4. State Henry’s Law.

  5. Why is molality preferred over molarity in temperature-based calculations?

🔹 Section B: Long Answer Questions (5 marks each)

  1. Explain any four methods of expressing concentration of solutions with formulae.

  2. Describe the effects of temperature and pressure on the solubility of gases in liquids.

  3. Differentiate between ideal and non-ideal solutions with suitable examples.

  4. What are colligative properties? Explain any two of them in brief.

  5. Explain the van’t Hoff factor. How does it affect molar mass calculations?

🔹 Section C: Fill in the Blanks (1 mark each)

  1. The component present in larger quantity in a solution is called __________.

  2. Vapour pressure of a solution is __________ than that of the pure solvent.

  3. Raoult’s law relates vapour pressure to __________ of the component.

  4. The pressure required to stop osmosis is called __________.

  5. A solution that obeys Raoult’s Law at all concentrations is called __________.

🔹 Section D: Multiple Choice Questions (1 mark each)

  1. Which of the following is not a colligative property?
    a) Boiling point elevation
    b) Vapour pressure
    c) Osmotic pressure
    d) Freezing point depression

  2. Mole fraction is a __________ quantity.
    a) Dimensionless
    b) Dependent on volume
    c) Dependent on mass
    d) None of these

  3. Henry’s law states that solubility of a gas is proportional to:
    a) Volume of gas
    b) Temperature
    c) Partial pressure of gas
    d) Density of gas

  4. In positive deviation from Raoult’s law, A–B interactions are:
    a) Stronger
    b) Weaker
    c) Same
    d) Non-existent

  5. The value of van’t Hoff factor (i) for KCl is approximately:
    a) 1
    b) 0.5
    c) 2
    d) 3

🔹 Section E: Glossary (Key Terms in Bengali)

TermBengali Meaning
Solutionদ্রবণ
Soluteদ্রব্য
Solventদ্রাবক
Concentrationঘনত্ব
Mole fractionমোল ভগ্নাংশ
Vapour pressureবাষ্পচাপ
Boiling pointস্ফুটনাঙ্ক
Freezing pointহিমাঙ্ক
Osmosisঅভিস্রবণ
Ideal solutionআদর্শ দ্রবণ
Deviationবিচ্যুতি
Associationযুক্তিকরণ
Dissociationবিযুক্তিকরণ
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Thursday, May 15, 2025

HS 1st year : Chemistry chapter 6 Equilibrium experiments

 

Experiment Title:

Study of Chemical Equilibrium – Effect of Concentration on the Position of Equilibrium

Objective:

To observe the effect of changing concentration on the position of equilibrium in a reversible reaction.

Materials Required:

  • Iron(III) chloride solution (FeCl₃)

  • Potassium thiocyanate solution (KSCN)

  • Distilled water

  • Test tubes

  • Dropper

  • Beaker

  • Glass rod

Chemical Reaction:

Fe3+(aq)+SCN−(aq)⇌FeSCN2+(aq)\text{Fe}^{3+}(aq) + \text{SCN}^-(aq) \rightleftharpoons \text{FeSCN}^{2+}(aq)
This reaction shows a reddish-brown complex formation, which is reversible.

Procedure:

  1. Preparation of Equilibrium Mixture:

    • Take about 5 mL of 0.002 M FeCl₃ solution in a test tube.

    • Add 5 mL of 0.002 M KSCN solution.

    • Mix well and observe the reddish-brown colour of FeSCN²⁺ complex indicating equilibrium.

  2. Effect of Adding Reactant (KSCN):

    • Take a small portion of the equilibrium mixture in another test tube.

    • Add a few drops of KSCN solution.

    • Observe the intensification of the reddish-brown colour (due to shift in equilibrium to the right).

  3. Effect of Adding Reactant (FeCl₃):

    • Take another portion of the original equilibrium mixture.

    • Add a few drops of FeCl₃ solution.

    • Observe the increase in colour intensity again (shift to the right).

  4. Effect of Dilution:

    • Take a third portion of the equilibrium mixture.

    • Add distilled water.

    • Observe the fading of the colour indicating a shift in equilibrium (can be interpreted depending on ion concentration changes).

Observation:

  • Addition of either Fe³⁺ or SCN⁻ ions deepens the colour of the complex.

  • This confirms that equilibrium shifts to the right (product side) when reactant concentration increases (as per Le Chatelier’s Principle).

Conclusion:

The position of chemical equilibrium is influenced by the concentration of reactants. Increasing the concentration of reactants shifts the equilibrium towards the formation of more product.

at No comments:

HS 1st year : Chemistry chapter 5 Thermodynamics experiments

 

Experiment 1: Determination of the Mechanical Equivalent of Heat (J) using Joule’s Calorimeter

Apparatus Required:
Joule’s calorimeter, battery, ammeter, voltmeter, stopwatch, rheostat, key, and connecting wires.

Procedure:

  1. Arrange the Joule’s calorimeter with stirrer and heating coil inside it.

  2. Measure the mass of water in the calorimeter.

  3. Note the initial temperature of the water.

  4. Complete the circuit using the battery, ammeter, voltmeter, and key.

  5. Close the key and start the stopwatch simultaneously.

  6. Keep the current flowing for a known time interval.

  7. Note the final temperature of the water.

  8. Use the known values of voltage (V), current (I), and time (t) to calculate the heat produced:

    H=VIt joulesH = VIt \, \text{joules}

  9. Compare the calculated heat with the heat gained by the water:

    H′=mcΔTH' = mc\Delta T

  10. The mechanical equivalent of heat J=HH′J = \frac{H}{H'}

Experiment 2: Determination of Specific Heat of a Liquid by the Method of Mixtures

Apparatus Required:
Calorimeter, thermometer, stirrer, water, and the liquid under test.

Procedure:

  1. Measure and record the mass of the calorimeter and water.

  2. Note the initial temperature of water.

  3. Heat the liquid to a known temperature.

  4. Pour the hot liquid into the calorimeter containing water.

  5. Stir gently and note the final temperature.

  6. Use the principle of calorimetry:

    Heat lost by liquid=Heat gained by water + calorimeter\text{Heat lost by liquid} = \text{Heat gained by water + calorimeter}

  7. Calculate the specific heat of the liquid using the formula.

at No comments:

HS1 Physics GRAVITATION Chapter 7: Experiments

 Title: Experiment to Measure Acceleration Due to Gravity (g) Using a Simple Pendulum

Objective: To determine the acceleration due to gravity (g) using a simple pendulum.

Materials Required:

  1. A rigid support with a hook

  2. A long, inextensible thread (approximately 1-2 meters)

  3. A small, heavy bob (metal sphere)

  4. Stopwatch

  5. Meter scale

  6. Protractor

Theory: The time period (T) of a simple pendulum is given by the formula:

where:

  • = Time period of the pendulum

  • = Length of the pendulum

  • = Acceleration due to gravity

From this formula, can be calculated using:

Procedure:

  1. Set up the simple pendulum by suspending the bob with the thread from the rigid support.

  2. Measure the length of the pendulum (L) from the point of suspension to the center of the bob using the meter scale.

  3. Displace the pendulum slightly (small angle, less than 10°) and release it without any push.

  4. Use the stopwatch to measure the time for 20 complete oscillations and record it.

  5. Calculate the time period (T) by dividing the recorded time by 20.

  6. Repeat the experiment 3 times for accuracy and take the average value of T.

  7. Substitute the values of L and T in the formula to calculate g.

Observations:

  • Length of the pendulum (L) = ______ cm

  • Time for 20 oscillations (Trial 1) = ______ s

  • Time for 20 oscillations (Trial 2) = ______ s

  • Time for 20 oscillations (Trial 3) = ______ s

  • Average time for 20 oscillations = ______ s

  • Time period (T) = Average time / 20 = ______ s

Calculation: Substitute the average value of T and the value of L in the formula:

Result: The calculated value of acceleration due to gravity (g) is ______ m/s².

Precautions:

  1. Ensure the amplitude of oscillations is small (less than 10°).

  2. The thread should be inextensible and should not have any knots.

  3. The bob should be heavy and spherical for smooth oscillations.

  4. The pendulum should not be affected by air currents.

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HS1 Physics LAWS OF MOTION Chapter 4: Experiments

 

Experiment Process for Demonstrating Laws of Motion

Aim:

To demonstrate Newton's Laws of Motion through simple experiments.

Materials Required:

  • A smooth wooden surface

  • A small wooden block

  • Spring balance

  • String

  • Pulley

  • Weights (different masses)

  • Stopwatch

  • Graph paper

Procedure:

1. Demonstrating Newton's First Law (Law of Inertia):

  1. Place the wooden block on the smooth surface.

  2. Gently push the block. Observe that it moves but stops after some time due to friction.

  3. Now, remove friction by making the surface even smoother (use a glass surface).

  4. Observe that the block moves farther, showing that an object continues in its state of rest or uniform motion unless acted upon by an external force.

2. Demonstrating Newton's Second Law (F=ma):

  1. Attach a string to the wooden block and pass it over the pulley.

  2. Attach a weight to the other end of the string.

  3. Measure the acceleration of the block using the stopwatch as it moves.

  4. Repeat with different weights and record the acceleration in each case.

  5. Plot a graph of force (weight) against acceleration to show that force is directly proportional to acceleration (F = ma).

3. Demonstrating Newton's Third Law (Action and Reaction):

  1. Place two identical blocks on a smooth surface, one of which has a spring-loaded surface.

  2. Push one block towards the other.

  3. Observe that both blocks move in opposite directions, showing that for every action, there is an equal and opposite reaction.

Observations:

Record your observations for each of the three experiments in a tabular format.

Conclusion:

  • The experiment demonstrates all three laws of motion effectively:

    • The first law (Inertia) is shown by the object's resistance to changes in motion.

    • The second law (F=ma) is verified by the direct proportionality of force and acceleration.

    • The third law (Action-Reaction) is shown by the interaction between two blocks.

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HS1 Physics MOTION IN A PLANE Chapter 3: Experiments

 

Experiment: Study of Motion in a Plane (Projectile Motion)

Objective:

To study the motion of a projectile and verify the independence of horizontal and vertical motions.

Apparatus Required:

  • Projectile launcher or a spring-loaded gun

  • Ball (small metal or plastic)

  • Carbon paper

  • Measuring scale or tape

  • Stopwatch (if needed)

  • Protractor

  • Plumb line

  • White chart paper

  • Stand with clamp

  • Ticker timer (for motion tracking, optional)

Theory:

Projectile motion is a form of motion in which an object moves in a curved path under the action of gravity. The horizontal and vertical motions are independent of each other, with:

  • Horizontal motion at constant velocity.

  • Vertical motion with constant acceleration due to gravity.

Equations of motion used:

  • Horizontal: x=uxtx = u_x t

  • Vertical: y=uyt+12gt2y = u_y t + \frac{1}{2} g t^2

Procedure:

  1. Setup the apparatus on a level table. Place the launcher at the edge and align it horizontally.

  2. Mount the chart paper on the floor below the edge of the table.

  3. Place carbon paper on top of the chart to mark the point of landing.

  4. Launch the projectile horizontally from a known height.

  5. Measure the horizontal distance (range) from the base of the table to the point of impact.

  6. Calculate the time of flight using the vertical height hh from which the projectile is launched:

    t=2hgt = \sqrt{\frac{2h}{g}}

  7. Calculate the horizontal velocity:

    ux=RangeTimeu_x = \frac{Range}{Time}

  8. Repeat the experiment 3–5 times to ensure accuracy.

Observations:

Record height, range, time of flight, and calculate the theoretical and experimental velocities.

TrialHeight (h)Range (x)Time of Flight (t)Velocity (u_x)
1
2
...

Result:

  • The calculated values verify the independence of horizontal and vertical motions.

  • Projectile follows a parabolic path, consistent with theoretical predictions.

Precautions:

  • Ensure the launcher is horizontal.

  • Measure the height accurately using a plumb line.

  • Use a flat and level surface for the experiment.

  • Avoid air drafts.

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