Download Engineering Chemistry Lab| Viva – Voce Questions

Engineering Chemistry Lab| Viva – Voce Questions
EXPERIMENT – 1 (ACIDIMETRY AND ALKALIMETRY)
1. Write the generalized equation for the determination of HCl using Na2CO3.
Ans:2HCl +
Na2CO3
→
2NaCl + H2O +
CO2
2. How many number of moles of HCl and Na2CO3 are taken?
Ans:2 moles of HCl and 1 mole of Na2CO3 are taken.
3. What is the indicator used in the reaction?
Ans:Methyl Orange
4. What is the color change at the end point of the reaction?
Ans:Yellow to pale pink.
5. What is the color of methyl orange in acidic medium?
Ans:Pale pink.
6. What is the color of methyl orange in basic medium?
Ans:Yellowish Orange
7. What are the other acid base indicators can be used?
Ans:Phenolphthalein, Methyl Red etc.
8. This reaction is an example for ___________.
Ans:Neutralization reaction.
9. What is the pH of the solution obtained by the reaction between strong acid and strong base?
Ans:pH = 7
11. What is a base?
Ans:A base is a substance which gives off a hydroxyl ion or a proton acceptor.
12. Under acidic conditions litmus paper turns to ______
Ans:Blue to red
13. What is the pH range of Methyl Orange indicator?
Ans:pH = 3 to 4
14. What is the significance of this experiment?
Ans:The principle of acidimetry and alkalimetry is used in manufacturing of soaps, drugs,
fertilizers etc., where acids and bases are used as raw materials.
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10. What is an acid?
Ans:An acid is substance which gives off proton or it is a proton donor.
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Engineering Chemistry Lab| Viva – Voce Questions
EXPERIMENT – 2 (REDOX TITRATIONS)
1. What is redox reaction?
Ans:A chemical reaction in which both oxidation and reduction reaction takes palce.
2. What is Oxidation?
Ans:Oxidation is
3. What is Reduction?
Ans:Reduction is
a) Loss of Electrons
b) Increase in Oxidation number
c) Gain of Oxygen
d) Loss of Hydrogen
a) Gain of Electrons
b) Decrease in Oxidation number
c) Loss of Oxygen
d) Gain of Hydrogen
4. What is the indicator used in this reaction?
Ans:No indicator is used. KMnO4 acts as a self-indicator.
5. What is the color change in this reaction?
Ans:
Colorless to pale pink.
6. What is the temperature to be maintained for this reaction to be carried out?
Ans:55 - 60°C
7. Why the reaction mixture is to be heated to 55 - 60°C?
Ans:At 60°C the rate of reaction will be more. For every 10°C rise in temperature, the rate of
reaction increases by 10 folds compared to at room temperature.
9. This reaction is an example for _________ reaction.
Ans:Autocatalytic reaction.
10. What is Oxidizing agent?
Ans:An oxidizing agent undergoes reduction and oxidizes the other species.
11. What is Reducing agent?
Ans:A reducing agent undergoes oxidation and reduces the other species.
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8. Write the Chemical equation for the reaction between potassium permanganate and oxalic acid.
Ans:2 MnO4- + 6H+ + 5 H2C2O4 → 2 Mn2+ + 8 H2O + 10 CO2
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Engineering Chemistry Lab| Viva – Voce Questions
EXPERIMENT – 3 (DETERMINATION OF Zn(II))
1. Write the chemical reaction between Zn (II) and potassium ferro cyanide solution.
Ans:3 Zn2+ +
2 K4[Fe(CN)6] →
K2Zn3[Fe(CN)6]
+
6 K+
2. The indicator used in the reaction is _______
Ans:Di Phenyl Amine(DPA)
3. The color change in the reaction is __________
Ans:Colorless to blue to greenish white precipitate
4. The greenish white precipitate is due to the formation of______
Ans:Due to the formation of sparingly soluble potassium zinc ferro cyanide complex.
5. What is the function of ammonium sulphate in the reaction?
Ans:it acts as a catalyst.
6. What is DPA?
Ans:DPA is di phenyl amine. It is a redox indicator.
7. This reaction is an example for __________ reactions.
Ans:Redox reactions.
EXPERIMENT – 4 (DETERMINATION OF Cu (II) USING EDTA)
2. What is the color change in this experiment?
Ans:When EBT is used, color change is from wine red to blue.
When FSBF is used, color change is from magenta to green.
3. What is the color of Metal EDTA complex in presence of FSBF indicator in alkaline medium?
Ans:Intense red colored complex.
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1. What are the indicators used in this experiment?
Ans:Erio Chrome Black – T and Fast Sulphon Black – F.
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Engineering Chemistry Lab| Viva – Voce Questions
EXPERIMENT – 5(ESTIMATION OF TOTAL HARDNESS)
1. Hardness is ________
Ans:It is the characteristic property of water of not giving lather with soap.
2. Hardness is due to ______
Ans:It is due to the dissolved bi-carbonates, chlorides and sulphates of calcium and
magnesium in water.
3. How many types of Hardness are there?
Ans:There are two types of hardness. Temporary hardness and Permanent Hardness.
4. Temporary Hardness is also called as _____________
Ans:Carbonate Hardness, Removable Hardness
5. Temporary Hardness is due to ________
Ans:Dissolved bicarbonates of Calcium and Magnesium.
6. Permanent Hardness is also called as _____________.
Ans:Non – Carbonate Hardness, Irremovable Hardness
7. Permanent Hardness is due to___________.
Ans:Dissolved chlorides and sulphates of Calcium and Magnesium.
8. The Principle involved in the estimation of total hardness in water sample is ___________.
Ans:Complexometric Titrations.
9. The complexing agent used in this experiment is ________.
Ans:EDTA (Ethylene di amine tetra acetic acid)
11. The indicators used in the complexometric titrations are also called as_____________.
Ans:Complexometric Indicators or Metal – Ion indicators.
12. The structure of EDTA is _______
Ans:-
13. Write the chemical reaction between metal ion and EDTA.
Ans:-
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10. What is the indicator used in this experiment?
Ans:EBT (Erio Chrome Balck – T )
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Engineering Chemistry Lab| Viva – Voce Questions
14. What are the chemicals used in this experiment?
Ans:EDTA, EBT indicator, pH = 10 buffer.
15. Which type of ligand is EDTA?
Ans:EDTA is a hexa dentate ligand.
16. What is the name of the buffer solution used in EDTA titration?
Ans:Ammonium chloride and Ammonia solution buffer.
17. Why only pH = 10 buffer has to be used?
Ans:At pH = 10, all protons in EDTA molecules are completely dissociated and complete
complexation with metal ions in water takes place.
18. What are the units of Hardness?
Ans:ppm or parts per million.
19. Why hardness is expressed in equivalents of calcium carbonate?
Ans:Calcium carbonate is most insoluble slt and its molecular weight and equivalent weights
are 100 and 50 respectively.
20. What is hard water?
Ans:The water which will not give lather with soap immediately is called hard water.
21. What is soft water?
Ans:The water which will give later with soap immediately is called soft water.
22. Why disodium salt of EDTA is much preferred than EDTA?
Ans:EDTA di sodium salt is more soluble in water when compared to pure EDTA.
24. How permanent hardness in water is removed?
Ans:Permanent hardness in water is removed by Lime soda method, zeolite method or Ionexchange method.
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23. How temporary hardness in water is removed?
Ans:By simple boiling, bicarbonates of calcium and magnesium are precipitated out as
carbonates of calcium and magnesium.
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Engineering Chemistry Lab| Viva – Voce Questions
EXPERIMENT – 6 (DETERMINATION OF pH)
1. What is pH?
Ans:pH is the negative logarithm of hydrogen ion concentration
pH = -log [H+]
2. Write the pH range?
Ans:pH range is from 0 to 14.
3. What happens when a base is added to an acid?
Ans:The pH value increases.
4. What is buffer solution?
Ans:The solution which resists the change in the pH even on the slight addition of acid or
base.
5. Name the electrode used in the determination of pH.
Ans:Glass combined electrode.
6. Why you need to calibrate a pH meter?
Ans:The characteristic of a pH electrode will change with time due to electrode coating and
aging. And even a pH electrode would be stable over time, pH electrodes cannot be produced with
identical characteristics.
In practice the response of a real pH sensor does not exactly follow the Nernst equation.
This difference between the theoretical and actual behavior of a pH electrode must be compensated
for. A calibration is required to match the pH meter to the current characteristics of the used pH
sensor.
7. What is pH of blood?
Ans:7.35 – 7.45.
9. What is pH of soil?
Ans:6-8
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8. What is pH of pure water?
Ans:At 27°C, pH = 6.83, at 25°C = 7.00, at 100°C = 6.14
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Engineering Chemistry Lab| Viva – Voce Questions
EXPERIMENT – 7 & 8 (CONDUCTOMETRIC TITRATIONS)
1. When strong acid combines with a strong base what type of reaction occurs?
Ans:Acid and a base combines to form salt and water. The reaction is called as neutralization
reaction.
2. Name the apparatus used for this method?
Ans:Conductivity meter with a conducitivity cell.
3. How conductance is related to the concentration of the ions?
Ans:The specific conductance is proportional to the concentration of ions in it.
4. How the end point for a particular reaction is calculated using this, titration method?
Ans:On plotting a graph between conductance and volume of the base, the point of
Intersection of the straight lines gives the end point.
5. Why conductance decreases on addition of NaOH to HCI ?
Ans:During the titration the fast moving hydrogen ions are replaced by the slow moving
Sodium ions, as a result the conductance of the solution decreases.
6. What is the unit for conductance?
Ans:The unit for conductance is mho or Siemens.
7. State Ohm’s law?
Ans:Ohm's law states that the current through a conductor between two points is directly
proportional to the potential difference across the two points. (V = IR)
8. What is specific conductivity?
Ans:It is the measure of the ability of the electrolytic solution to conduct electricity.
10. What is molar conductivity?
Ans:The conductance of that volume of solution containing one mole of an electrolyte is
known as molar conductivity. It is denoted by Λm or μ.
11. What is conductance?
Ans:It is the tendency of a material to allow the flow of current through it. It is the reciprocal
of resistance.
12. Name the conductivity which is measured during conductometric titrations?
Ans:Equivalent conductance.
13. The electrical conductivity of a solution depends upon_____________.
Ans:The number of ions present in the solution and their mobility.
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9. What is equivalent conductivity?
Ans:The conductance of that volume of solution containing one equivalent of an electrolyte
is known as equivalent conductivity. It is denoted by Λ.
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Engineering Chemistry Lab| Viva – Voce Questions
EXPERIMENT – 9 (POTENTIOMETRIC TITRATIONS)
1. What are the electrodes used in the potentiometric titrations?
Ans:Reference Electrode – Calomel electrode
Indicator electrode – Platinum electrode
2. What is the Principle of Potentiometric titration?
Ans:Nernst equation
3. What is the indicator electrode?
Ans:The electrode with which we measure the potential of the test solution is called
indicator electrode.
4. What is reference electrode? Give examples.
Ans:The potential of unknown electrode can be measured by coupling it with another
electrode called reference electrode whose potential is already known or arbitrarily zero. Example:
calomel electrode, standard hydrogen electrode.
5. What is calomel electrode?
Ans:It is a secondary reference electrode containing mercury, mercurous chloride and
solution of KCl.
6. Write the E° values for a calomel electrode.
Ans:1. In 1N Kcl solution = 02800v
2. In saturated KCl solution = 0.2422v
3. In 0.1N KCl solution = 0.3338v
EXPERIMENT – 10 (Colorimetry)
1.
2.
3.
4.
5.
What is Beer’s law?
What is Lambert’s law?
What is the principle involved in colorimetry?
What is the wave length region of visible region?
Which is the source of light in colorimetry?
Ans:- Tungsten lamp.
Apart from above..generalized questions will be asked.
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7. What is the advantage of potentiometric titrations?
Ans:they are particularly useful with colored or turbid solutions and for detecting the
presence of unsuspected species.
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