1. Using the NaCI-H20 phase diagram below, please answer the following questions
ID: 702269 • Letter: 1
Question
1. Using the NaCI-H20 phase diagram below, please answer the following questions. 50 Liquid (brine) 40 0 Salt 30 Ice 20 Liquid (brine) o-10 Liquid (brine 10 20 -10 Ice+ Salt -20 Naci 30 H20 100 10 90 20 80 30 70 0 Composition (wt%) (a) How many pounds of ice can 1 Ib of NaCI melt at 30 oF? At 20 °F? (b) The Dead Sea has a salinity of 33.7%. Assuming that this is the wt% of NaCl in water, how many phases are present in the Dead Sea and what are they? If the Atlantic Ocean is only 3.7 wt% NaCl on average, how many phases are present and what are they? Assume a temperature of 40 °F. (c) The Titanic sank after hitting an iceberg. If the temperature was -2 oC that night, what was the salinity in the ocean in order to have the coexistence of ice and salt water?Explanation / Answer
a) At 30 F. In Ice+liquid brine region, NaCl % in liquid water = ~3%
=> 1 lb NaCl can melt = 1/.03=33 lb water
At 20 F. In Ice+liquid brine region, NaCl % in liquid water = ~9%
=> 1 lb NaCl can melt = 1/.09=11 lb water
b) in Dead sea, At 40 F, at 33.7% salinity, it lies in salt + liquid region. Therefore, two phases exist in dead sea
in Atlantic, At 40 F, at 3.7% salinity, it lies in liquid region. Therefore, one phases exist in Atlantic
c) As can be seen from plot. For ice and liquid to exist at - 2 C, Salinity should lie in ~0 to 2 %
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