Question

1) A room is 10.0 m by 7.5 m by 2.7 m is filled with air at 22^oC and 1 atm. The average molar mass of air is 28.8 g/mol. Find the number of moles of air to fill the room and the weight of the air in kg.

2) If it takes exactly 4 min. to completely melt a 2.0 kg block of ice at 0.0° C, how much power is needed? (For water Lf = 334 kJ/kg and Lv = 2257 kJ/kg.)

3) A steel rod 30.0 m long, installed when the temperature was 10°C, is in a bridge that heats up to 40^oC on a hot summer day. Steel's coefficient of linear expansion is 1.2 × 10-5 K-1. The bridge is built so the rod has an expansion space of 5 cm. Is this enough space? What is the increase in the length of the rod, in mm?

4) A 1 kg block of iron is heated. How much heat in joules must it absorb to raise its temperature form 25.0° C to 1000.0° C? (The specific heat for iron is 113 cal/kg ∙ °C.)

Answer 1