a) Calculate the amount of water that went through his body under the assumption that he consumed on average 2 liters per day and lived for 30 years.
b) How many molecules that passed through the body of this person are in 1 liter of NYC drinking water? Assume that all water reservoirs on the earth are well mixed over the past 200,000 years which means that those molecules used by our ancestor are evenly distributed in the hydrological cycle (18 grams (= 18 ml) of water contain about 6·1023 molecules, use the reservoir size from the book or from the class' web site). Clearly write down how you obtained your result.
3) (6 points) Imagine a humid day sitting in a bar with a glass of cold beer. Water from the atmosphere is condensing on the glass.
a) Calculate the temperature change of the beer due to heat released by the condensation process. The heat capacity of the glass may be neglected. The glass contains 200 ml of beer, and one gram of water is condensing (heat capacity of water (beer): 1 cal per gram per °C, phase change from vapor to liquid releases 539 cal/g).
b) What assumptions are we making in the above calculation?
4) (8 points) Particularly during cold winter days, we experience very dry air in our apartments.
a) Can you explain this phenomenon?
b) Many of us are probably using humidifiers in order to make the air more comfortable. Consider a room of the size of 150 square feet that is 9 ft high. The temperature of the room is 20°C, relative humidity initially 30%. Assuming that there is no exchange of air between the room and the rest of the apartment, how much water do you have to evaporate in order to increase the relative humidity to 60%? Use the vapor pressure curve for H2O (fig) to determine what the approximate water vapor pressure difference is between 30% and 60% relative humidity. Then convert this pressure difference into a quantity of H2O knowing that 1 mbar of H2O vapor pressure is equivalent to 0.74g of water/m3 at 20°C.
