The enthalpy of fusion of water is \(6.01 \mathrm{~kJ} / \mathrm{mol}\). Sunlight striking Earth's surface supplies \(168 \mathrm{~W}\) per square meter \((1 \mathrm{~W}=1 \mathrm{watt}=1 \mathrm{~J} / \mathrm{s}) .(\) a) Assuming that melting of ice is due only to energy input from the Sun, calculate how many grams of ice could be melted from a 1.00 square meter patch of ice over a \(12-\mathrm{h}\) day. \((\mathbf{b})\) The specific heat capacity of ice is \(2.032 \mathrm{~J} / \mathrm{g}^{\circ} \mathrm{C}\). If the initial temperature of a 1.00 square meter patch of ice is \(-5.0^{\circ} \mathrm{C},\) what is its final temperature after being in sunlight for \(12 \mathrm{~h}\), assuming no phase changes and assuming that sunlight penetrates uniformly to a depth of \(1.00 \mathrm{~cm} ?\)

Short Answer

Expert verified
A short version of the answer to the question is as follows: a) About 21,726 grams of ice can be melted from a 1.00 square meter patch of ice over a 12-hour day, assuming that melting is due only to energy input from the Sun. b) The final temperature of a 1.00 square meter patch of ice after being in sunlight for 12 hours, assuming no phase changes and uniform penetration to a depth of 1.00 cm, is approximately 384.4°C.

Step by step solution

01

a) Calculating the mass of melted ice

First, we need to calculate the total energy input from the Sun in 12 hours. Energy input rate is 168 J/s (given). We need to find the total energy input in 12 hours. 12 hours = 12 * 60 * 60 seconds Energy input = (Energy input rate) x (Time) Energy input = 168 J/s x (12 * 60 * 60 s) \[Energy\:input = 7,257,600\:J\] We are given the enthalpy of fusion of water, denoted by ∆H, which is 6.01 kJ/mol. To convert it to joules, multiply by 1000. ∆H = 6.01 kJ/mol * 1000 J/kJ \[\Delta H = 6,010\:J/mol\] Next, we need to find the number of moles (n) of ice that can be melted using this energy. n = (Energy input) / ∆H n = 7,257,600 J / 6,010 J/mol \[n \approx 1,207\:moles\] Now, we can convert moles to grams using the molar mass of water (18 g/mol). Mass = n * (molar mass of water) Mass = 1,207 moles * 18 g/mol \[Mass \approx 21,726\:grams\] So, about 21,726 grams of ice can be melted from a 1.00 square meter patch of ice over a 12-hour day.
02

b) Calculating the final temperature of the ice

Now, we are given the specific heat capacity of ice (c) which is 2.032 J/g°C. We also know the initial temperature of the ice (T_initial) is -5.0°C. Given the ice is 1.00 square meter in area and the sunlight penetrates uniformly to a depth of 1.00cm, we can calculate the volume of the ice. Volume of ice = Area x Depth \[Volume\:of\:ice = 1.00\:m^2 * 0.01\:m = 0.01\:m^3\] Next, we will assume the density of ice as 917 kg/m³, which is a common value for ice. Now, we can calculate the mass of the ice patch: Mass of ice = (Volume of ice) x (Density of ice) \[Mass\:of\:ice = 0.01\:m^3 * 917\:kg/m^3 = 9.17\:kg\] Convert the mass to grams: Mass of ice = 9.17 kg × 1000 g/kg \[Mass\:of\:ice = 9,170\:g\] The energy input in 12 hours is the same as before: Energy input = 7,257,600 J Now, we can use the specific heat capacity formula to find the final temperature (T_final) of the ice. Energy input = Mass x c x (T_final - T_initial) 7,257,600 J = 9,170 g x 2.032 J/g°C x (T_final - (-5°C)) \[7,257,600 = 18,635(T_{final}+5)\] Divide both sides by 18,635: \(T_{final}+5 = \frac{7,257,600}{18,635}\) \(T_{final}+5 \approx 389.4\) Now, subtract 5 from both sides to find the final temperature: \[T_{final} \approx 384.4^{\circ}C\] The final temperature of the ice after being in sunlight for 12 hours, assuming no phase changes and uniform penetration to a depth of 1.00 cm, is approximately 384.4°C.

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Most popular questions from this chapter

A reaction that contributes to the depletion of ozone in the stratosphere is the direct reaction of oxygen atoms with ozone: $$ \mathrm{O}(g)+\mathrm{O}_{3}(g) \longrightarrow 2 \mathrm{O}_{2}(g) $$ At \(298 \mathrm{~K}\) the rate constant for this reaction is $4.8 \times 10^{5}\( \)M^{-1} \mathrm{~s}^{-1}$. (a) Based on the units of the rate constant, write the likely rate law for this reaction. (b) Would you expect this reaction to occur via a single elementary process? Explain why or why not. (c) Use \(\Delta H_{f}^{\circ}\) values from Appendix \(\mathrm{C}\) to estimate the enthalpy change for this reaction. Would this reaction raise or lower the temperature of the stratosphere?

(a) What is the primary basis for the division of the atmosphere into different regions? (b) Name the regions of the atmosphere, indicating the altitude interval for each one.

(a) How are the boundaries between the regions of the atmosphere determined? (b) Explain why the stratosphere, which is about \(35 \mathrm{~km}\) thick, has a smaller total mass than the troposphere, which is about \(12 \mathrm{~km}\) thick.

(a) Distinguish between photodissociation and photoionization. (b) Use the energy requirements of these two processes to explain why photodissociation of oxygen is more important than photoionization of oxygen at altitudes below about \(90 \mathrm{~km}\).

(a) What is the difference between chlorofluorocarbons and hydrofluorocarbons? (b) Why are hydrofluorocarbons potentially less harmful to the ozone layer than CFCs?

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