SURE SHOT QUESTIONS
Solution
1. Q: Explain why on addition of 1 mol of NaCl to 1 litre of water, the boiling point of water increases,
while addition of 1 mol of methyl alcohol to one litre of water decreases its boiling point.
Ans: NaCl is a non volatile solute hence elevation in boiling point takes place, but methyl alcohol is a
volatile miscible liquid which decrease boiling point.
2. Concentration terms such as mass percentage, ppm, mole fraction and molality are independent of
temperature, however molarity is a function of temperature. Explain.
Ans: Molarity is a function of volume which changes with temperature.
3. Explain the Painful condition known as bends with the help of Henry’s law.
Ans: Scuba divers must cope with high concentrations of dissolved gases while breathing air at high
pressure underwater. Increased pressure increases the solubility of atmospheric gases in blood. When
the divers come towards surface, the pressure gradually decreases. This releases the dissolved gases and
leads to the formation of bubbles of nitrogen in the blood.
4. Explain Feeling of weakness and discomfort in breathing at high altitude.
Ans: Due to less pressure of air leads less solubility of oxygen in blood.
5. Why soda water bottle kept at room temperature fizzes on opening?
Ans: Due to decrease of solubility of CO2 gas
6. Why is the vapour pressure of an aqueous solution of glucose lower than that of water?
Ans: Glucose is a non volatile solute hence lowering of vapour pressure take place.
7. How does sprinkling of salt help in clearing the snow covered roads in hilly areas? Explain the
phenomenon involved in the process.
Ans: sprinkling of salt decrease the freezing point of water so ice melts easily at the atmospheric
temperature.
8. Solubility of gas decrease with increase in temperature. Explain.
Ans: Enthalpy of solution is exothermic for gas liquid solution. So on the basis of le chattelier’s principle
solubility decrease by increase in temperature.
9. People taking a lot of salt or salty food experience water retention in tissue cells. Why?
Ans: Water will move into its cells through osmosis. People taking a lot of salt or salty food experience
water retention in tissue cells and intercellular spaces because of osmosis. The resulting puffiness or
swelling is called edema.
10. Based on solute-solvent interactions, arrange the following in order of increasing solubility in n-octane
and explain. Cyclohexane, KCl, CH3 OH, CH3 CN.
Ans: n-octane is a non-polar solvent hence solubility decrease as the polarity of solvent increase. Hence
solubility as KCl < CH3OH < CH3CN < Cyclohexane
11. What type of deviation from Rault’s law is shown By chloroform and acetone solution ? Give reason.
Ans:- Negative deviation, as the molecular attraction between chloroform and acetone increase due to
formation of H bonding.
12. Differentiate between Ideal solution and Non-ideal solution.
Ideal solution Non-ideal solution
(i) Obeys Rault’s Law (i) Doesnot obey Rault’s Law
(ii) ΔH solution = 0 (ii) ΔH solution ≠ 0
(iii) ΔV = 0 (iii) ΔV≠ 0
13. What is Henery’s Law? Write its one application.
Ans:- Solubility of gas in a liquid id directly proportional to its partial pressure. P = K HX
Application:- (i) In making soft drinks (ii) Explain medical condition Bend by Scuba divers.
14. What are colligative properties? Which colligative property is used to determine molecular mass of
1|P ag e
, biomolecules such as protein? Explain.
Ans:- Properties of dilute solution which depends on the number of moles of non-volatile solute are
called colligative properties.
Osmotic pressure is used to determine molecular mass of biomolecules such as protein, since it can be
determined at room temperature.
15. Explain Reverse Osmosis.
Ans: If pressure applied to the solution is more than osmotic pressure then solvent pass the semi
permeable membrane from solution to solvent is called Reverse Osmosis. It is used to desaline salt
water.
Electrochemistry
1. Can absolute electrode potential of an electrode be measured?
Ans: No, It is measured with the reference of standard H electrode.
2. Under what condition is ECell = 0 or ΔG = 0?
Ans: When the cell reaction reaches equilibrium.
3. What does the negative sign in the expression E0 Zn2+ /Zn = − 0.76 V mean?
Ans: Zn is more reactive than hydrogen.
4. What is electrode potential?
Ans: The potential difference between the two electrodes of a galvanic cell.
5. Why is alternating current used for measuring resistance of an electrolytic solution?
Ans: To avoid polarization around electrodes.
6. How will the pH of brine (aq. NaCl solution) be affected when it is electrolysed?
Ans:pH increases due to formation of NaOH
7. Unlike dry cell, the mercury cell has a constant cell potential throughout its useful life. Why?
Ans: No ion involved
8. Solutions of two electrolytes ‘A’ and ‘B’ are diluted. The Λm of ‘B’ increases 1.5 times while that of A
increases 25 times. Which of the two is a strong electrolyte? Justify your answer.
Ans: A, Since it follows Debye Huckel Osanger equation
9. When acidulated water (dil.H2 SO4 solution) is electrolysed, will the pH of the solution be affected?
Justify your answer.
Ans: No, Since electrolysis produce H2 at cathode and O2 at anode.H2SO4 remain in solution.
10. What advantage do the fuel cells have over primary and secondary batteries?
Ans: Primary batteries contain a limited amount of reactants and are discharged when the reactants
have been consumed. Secondary batteries can be recharged but take a long time to recharge. Fuel cell
runs continuously as long as the reactants are supplied to it and products are removed continuously.
11. Write the cell reaction of a lead storage battery when it is discharged. How does the density of the
electrolyte change when the battery is discharged?
Ans: Pb + PbO2 + 2H2 SO4 → 2PbSO4 + 2H2O
Density of electrolyte decreases as water is formed and sulphuric acid is consumed as the product
during discharge of the battery.
12. Can you store copper sulphate solutions in a zinc pot?
Ans: No Zn is more reactive than Cu hence Zn dissolve in CuSO4.
13. Why does the conductivity of a solution decrease with dilution?
Ans: Due to decrease in number of ions per unit volume.
14. State Faraday’s Laws of Electrolysis
Ans:- 1st Law: Mass of substance deposited on electrode in electrolysis is directly proportional to charge
supplied through it. m ∝ Q
2nd Law: If same quantity of electricity passing through the electrolytic solution mass deposited is
directly proportional to equivalent mass. m ∝ E
2|P ag e
Solution
1. Q: Explain why on addition of 1 mol of NaCl to 1 litre of water, the boiling point of water increases,
while addition of 1 mol of methyl alcohol to one litre of water decreases its boiling point.
Ans: NaCl is a non volatile solute hence elevation in boiling point takes place, but methyl alcohol is a
volatile miscible liquid which decrease boiling point.
2. Concentration terms such as mass percentage, ppm, mole fraction and molality are independent of
temperature, however molarity is a function of temperature. Explain.
Ans: Molarity is a function of volume which changes with temperature.
3. Explain the Painful condition known as bends with the help of Henry’s law.
Ans: Scuba divers must cope with high concentrations of dissolved gases while breathing air at high
pressure underwater. Increased pressure increases the solubility of atmospheric gases in blood. When
the divers come towards surface, the pressure gradually decreases. This releases the dissolved gases and
leads to the formation of bubbles of nitrogen in the blood.
4. Explain Feeling of weakness and discomfort in breathing at high altitude.
Ans: Due to less pressure of air leads less solubility of oxygen in blood.
5. Why soda water bottle kept at room temperature fizzes on opening?
Ans: Due to decrease of solubility of CO2 gas
6. Why is the vapour pressure of an aqueous solution of glucose lower than that of water?
Ans: Glucose is a non volatile solute hence lowering of vapour pressure take place.
7. How does sprinkling of salt help in clearing the snow covered roads in hilly areas? Explain the
phenomenon involved in the process.
Ans: sprinkling of salt decrease the freezing point of water so ice melts easily at the atmospheric
temperature.
8. Solubility of gas decrease with increase in temperature. Explain.
Ans: Enthalpy of solution is exothermic for gas liquid solution. So on the basis of le chattelier’s principle
solubility decrease by increase in temperature.
9. People taking a lot of salt or salty food experience water retention in tissue cells. Why?
Ans: Water will move into its cells through osmosis. People taking a lot of salt or salty food experience
water retention in tissue cells and intercellular spaces because of osmosis. The resulting puffiness or
swelling is called edema.
10. Based on solute-solvent interactions, arrange the following in order of increasing solubility in n-octane
and explain. Cyclohexane, KCl, CH3 OH, CH3 CN.
Ans: n-octane is a non-polar solvent hence solubility decrease as the polarity of solvent increase. Hence
solubility as KCl < CH3OH < CH3CN < Cyclohexane
11. What type of deviation from Rault’s law is shown By chloroform and acetone solution ? Give reason.
Ans:- Negative deviation, as the molecular attraction between chloroform and acetone increase due to
formation of H bonding.
12. Differentiate between Ideal solution and Non-ideal solution.
Ideal solution Non-ideal solution
(i) Obeys Rault’s Law (i) Doesnot obey Rault’s Law
(ii) ΔH solution = 0 (ii) ΔH solution ≠ 0
(iii) ΔV = 0 (iii) ΔV≠ 0
13. What is Henery’s Law? Write its one application.
Ans:- Solubility of gas in a liquid id directly proportional to its partial pressure. P = K HX
Application:- (i) In making soft drinks (ii) Explain medical condition Bend by Scuba divers.
14. What are colligative properties? Which colligative property is used to determine molecular mass of
1|P ag e
, biomolecules such as protein? Explain.
Ans:- Properties of dilute solution which depends on the number of moles of non-volatile solute are
called colligative properties.
Osmotic pressure is used to determine molecular mass of biomolecules such as protein, since it can be
determined at room temperature.
15. Explain Reverse Osmosis.
Ans: If pressure applied to the solution is more than osmotic pressure then solvent pass the semi
permeable membrane from solution to solvent is called Reverse Osmosis. It is used to desaline salt
water.
Electrochemistry
1. Can absolute electrode potential of an electrode be measured?
Ans: No, It is measured with the reference of standard H electrode.
2. Under what condition is ECell = 0 or ΔG = 0?
Ans: When the cell reaction reaches equilibrium.
3. What does the negative sign in the expression E0 Zn2+ /Zn = − 0.76 V mean?
Ans: Zn is more reactive than hydrogen.
4. What is electrode potential?
Ans: The potential difference between the two electrodes of a galvanic cell.
5. Why is alternating current used for measuring resistance of an electrolytic solution?
Ans: To avoid polarization around electrodes.
6. How will the pH of brine (aq. NaCl solution) be affected when it is electrolysed?
Ans:pH increases due to formation of NaOH
7. Unlike dry cell, the mercury cell has a constant cell potential throughout its useful life. Why?
Ans: No ion involved
8. Solutions of two electrolytes ‘A’ and ‘B’ are diluted. The Λm of ‘B’ increases 1.5 times while that of A
increases 25 times. Which of the two is a strong electrolyte? Justify your answer.
Ans: A, Since it follows Debye Huckel Osanger equation
9. When acidulated water (dil.H2 SO4 solution) is electrolysed, will the pH of the solution be affected?
Justify your answer.
Ans: No, Since electrolysis produce H2 at cathode and O2 at anode.H2SO4 remain in solution.
10. What advantage do the fuel cells have over primary and secondary batteries?
Ans: Primary batteries contain a limited amount of reactants and are discharged when the reactants
have been consumed. Secondary batteries can be recharged but take a long time to recharge. Fuel cell
runs continuously as long as the reactants are supplied to it and products are removed continuously.
11. Write the cell reaction of a lead storage battery when it is discharged. How does the density of the
electrolyte change when the battery is discharged?
Ans: Pb + PbO2 + 2H2 SO4 → 2PbSO4 + 2H2O
Density of electrolyte decreases as water is formed and sulphuric acid is consumed as the product
during discharge of the battery.
12. Can you store copper sulphate solutions in a zinc pot?
Ans: No Zn is more reactive than Cu hence Zn dissolve in CuSO4.
13. Why does the conductivity of a solution decrease with dilution?
Ans: Due to decrease in number of ions per unit volume.
14. State Faraday’s Laws of Electrolysis
Ans:- 1st Law: Mass of substance deposited on electrode in electrolysis is directly proportional to charge
supplied through it. m ∝ Q
2nd Law: If same quantity of electricity passing through the electrolytic solution mass deposited is
directly proportional to equivalent mass. m ∝ E
2|P ag e
