Q1) The latent heat of vaporization, v L , has units of (A) joules/degrees Celsi

Question

Q1) The latent heat of vaporization, v

L , has units of

(A) joules/degrees Celsius. (B) newtons. (C) watts. (D) joules/kilogram. (E) joules. Q2) The accepted value for the latent heat of vaporization of liquid nitrogen is 199,200 J/kg. How much energy, in Joules is required to completely vaporize 2.0 kg of liquid nitrogen? Q3) The accepted value for the latent heat of vaporization of liquid nitrogen is 199,200 J/kg. If the rate of mass conversion is entirely due to a heating element that delivers 150 J/s (or 150 W), how long will it take, in seconds, for the heating element to completely vaporize 2.0 kg of liquid nitrogen? Q4) Patrick and Domonique are performing the Vaporization of Liquid Nitrogen lab. They notice that when they turn on the power supply the ammeter says the current in the electrical circuit is 0.75 A. They should (A) adjust the power supply so that the current is decreased to 0.5 A. (B) adjust the power supply so that the current is increased to 1.0 A. (C) panic. (D) be thankful that the previous lab group had left the power supply set exactly where it should be for this experiment.

Q5) Patrick and Domonique are performing the Vaporization of Liquid Nitrogen lab and they determine that the rate of mass conversion due to the heating element is 15 g/s. By what factor would this rate change if the power of the heating element were tripled? (A) It would double. (B) It would triple. (C) It would be one-third as much. (D) It would be one-half as much (E) It would be about six times greater. (F) It would be about one-sixth as much.

Explanation / Answer

1. (D) joules/kilogram

2.  latent heat of vaporization of liquid nitrogen is 199,200 J/kg

so heat to vaporize 2 kg = 199200*2 = 398400 J

3. Rate of heat supply = 150 J/s

So time to vaporize completely = 398400/150 = 2656 s

4. Depends on what was the operating conditon provided to you in lab. You have to answer this.

5. If power is tripled, the mass conversion rate will also triple, since it will be getting 3 times heat in same time.

B) it would triple

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