Q. A 1 kg block of ice at 0°C is placed in 2 kg of water at 80°C. What will be the final temperature of the mixture? (Assume no heat loss to the surroundings) (2019)
A.0°C
B.40°C
C.60°C
D.80°C
Solution
Using the principle of conservation of energy, the heat lost by water equals the heat gained by ice. The final temperature will be 0°C as the ice will melt.
Q. A 1 kg block of metal at 100°C is placed in 2 kg of water at 20°C. Assuming no heat loss to the surroundings, what is the final temperature of the system? (Specific heat of water = 4.18 kJ/kg°C, specific heat of metal = 0.9 kJ/kg°C) (2020)
A.25°C
B.30°C
C.35°C
D.40°C
Solution
Using the principle of conservation of energy, set heat lost by metal equal to heat gained by water to find the final temperature.
Q. A 1 kg block of metal at 100°C is placed in 2 kg of water at 20°C. What is the final temperature of the system? (Specific heat of water = 4.18 J/g°C, specific heat of metal = 0.9 J/g°C) (2021)
A.25°C
B.30°C
C.35°C
D.40°C
Solution
Using conservation of energy: m1*c1*(T_initial - T_final) = m2*c2*(T_final - T_initial). Solving gives T_final = 35°C.
Q. A 100 g piece of metal at 100°C is placed in 200 g of water at 20°C. What will be the final temperature of the system? (Specific heat of water = 4.2 J/g°C, specific heat of metal = 0.5 J/g°C) (2023)
A.30°C
B.40°C
C.50°C
D.60°C
Solution
Using the heat transfer equation, we can find the final temperature to be 50°C.
Q. A 2 kg block of metal at 100°C is placed in 1 kg of water at 20°C. What is the final temperature of the system? (Specific heat of water = 4.2 J/g°C, specific heat of metal = 0.9 J/g°C) (2021)
A.30°C
B.40°C
C.50°C
D.60°C
Solution
Using the heat transfer equation, the final temperature can be calculated to be 50°C.
Q. A gas is compressed isothermally from a volume of 4 L to 1 L at a constant temperature of 300 K. If the initial pressure is 1 atm, what is the final pressure?
A.4 atm
B.3 atm
C.2 atm
D.1 atm
Solution
Using Boyle's Law, P1V1 = P2V2, we find P2 = P1 * (V1/V2) = 1 atm * (4 L / 1 L) = 4 atm.
Q. A refrigerator removes heat from the inside at a rate of 200 J/s and expels it to the surroundings at a rate of 250 J/s. What is the coefficient of performance (COP) of the refrigerator? (2023)
Q. If 200 g of water at 80°C is mixed with 300 g of water at 20°C, what will be the final temperature of the mixture? (Assume no heat loss to the surroundings)
A.30°C
B.40°C
C.50°C
D.60°C
Solution
Using the formula m1c1T1 + m2c2T2 = (m1 + m2)cTfinal, we find Tfinal = 40°C.
Q. If the volume of a gas is doubled at constant temperature, what happens to its pressure?
A.It doubles
B.It halves
C.It remains the same
D.It quadruples
Solution
According to Boyle's Law, at constant temperature, pressure is inversely proportional to volume. Therefore, if the volume is doubled, the pressure is halved.
