Specific latent heats of fusion and vaporization - Jamb Physics Past Questions and Answers

Question 1:

• JAMB 1979

All the heat generated in a 5 ohms resistor by 2A flowing for 30 seconds is used to evaporate 5g of a liquid at its boiling point. Which of the following is the correct value of the specific latent heat of the liquid?

A. 120J
B. 60Jg^-1
C. 120Jg^-1
D. 1500J
E. 1500Jg^-1

Question 2:

• JAMB 1980

a calorimeter of thermal capacity 80j contains 20g of water at 25^oC. Water at 100^oC is added so that the final temperature of the set-ups is 50^oC. The amount of water added is (Heat capacity of water = 4.18J/g/^oC)

A. 20g
B. 25g
C. 45g
D. 50g
E. 100g

Question 3:

• JAMB 1982

250g of lead at 170^oC is dropped into 100g of water at 0^oC. If the final temperature is 12^oC, the specific heat of lead is (specific heat of water is 4,200J/kg^oC)

A. 39.5J/kg^oC
B. 50.4J/kg^oC
C. 127.6J/kg^oC
D. 154.6J/kg^oC
E. 173.4J/kg^oC

Question 4:

• JAMB 1982

In copper plating, a current of 0.5A is allowed for cathode area of 100cm². If this current is maintained constant for 100 minutes, the thickness of the copper deposited will be approximately (the electrochemical equivalent of copper = 0.0003g/^oC, density of copper = 10^-4g/cm³ )

A. 10^-2mm
B. 10^-3mm
C. 10^-4mm
D. 10^-5mm
E. 10^-6mm

Question 5:

• JAMB 1982

A heater marked 50W will evaporate 0.005kg of boiling water in 50 seconds. The specific latent heat of vaporization of water in J/kg is

A. 5.0 x 10⁶
B. 1.0 x 10⁶
C. 2.5 x 10⁶
D. 2.5 x 10⁵
E. 5.0 x 10⁵