Textbook Question
What is the molarity of Na+ in a solution of NaCl whose salinity is 5.6 if the solution has a density of 1.03 g>mL?
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Ch.18 - Chemistry of the Environment
Chapter 18, Problem 39b
The enthalpy of evaporation of water is 40.67 kJ/mol. Sunlight striking Earth's surface supplies 168 W per square meter (1 W = 1 watt = 1 J/s). (b) The specific heat capacity of liquid water is 4.184 J/g°C. If the initial surface temperature of a 1.00 square meter patch of ocean is 26 °C, what is its final temperature after being in sunlight for 12 h, assuming no phase changes and assuming that sunlight penetrates uniformly to depth of 10.0 cm?
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Calculate the total energy supplied by sunlight over 12 hours. Use the formula: Energy (J) = Power (W) × Time (s). Convert 12 hours into seconds and multiply by the power per square meter (168 W/m²) to find the total energy in joules.
Determine the mass of the water affected by sunlight. Use the formula: Mass (g) = Volume (cm³) × Density (g/cm³). Calculate the volume of water by multiplying the area (1.00 m² converted to cm²) by the depth (10.0 cm). Use the density of water, which is approximately 1 g/cm³, to find the mass.
Use the specific heat capacity formula to find the change in temperature. The formula is: q = m × c × ΔT, where q is the energy absorbed, m is the mass of water, c is the specific heat capacity, and ΔT is the change in temperature. Rearrange the formula to solve for ΔT: ΔT = q / (m × c).
Substitute the values into the rearranged formula. Use the total energy calculated in step 1 for q, the mass calculated in step 2 for m, and the specific heat capacity given (4.184 J/g°C) for c.
Add the change in temperature (ΔT) to the initial temperature (26 °C) to find the final temperature of the water after 12 hours of sunlight exposure.
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Textbook Question
The enthalpy of evaporation of water is 40.67 kJ/mol. Sunlight striking Earth's surface supplies 168 W per square meter (1 W = 1 watt = 1 J/s). (a) Assuming that evaporation of water is due only to energy input from the Sun, calculate how many grams of water could be evaporated from a 1.00 square meter patch of ocean over a 12-h day
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