Problem 2. Liquid nitrogen, which has a boiling point of(adsbygoogle = window.adsbygoogle || []).push({});

77 K, is commonly used to cool substances to

low temperatures.

How much energy must be removed from

1.4 kg of gaseous nitrogen at 77 K for it to

completely liquefy? Assume the latent heat

of liquid nitrogen is 2.01 *10^5 J/kg Answer

in units of J.

Problem 4.

You have collected exactly 2200 aluminum

cans for recycling, each with a mass of 14.1 g.

How much energy is needed to melt them if

their initial temperature is 26.8 degrees C? Assume

the specific heat, the latent heat and the

melting point of aluminum are 899 J/kg * degrees C,

3.97*10^5 J/kg and 660.4degreesC respectively. An-

swer in units of J.

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