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Ch.18 - Chemistry of the Environment
All textbooksBrown 14th EditionCh.18 - Chemistry of the EnvironmentProblem 36
Chapter 18, Problem 36

The atmosphere of Mars is 96% CO2, with a pressure of approximately 6 * 10⁻³ atm at the surface. Based on measurements taken over a period of several years by the Rover Environmental Monitoring Station (REMS), the average daytime temperature at the REMS location on Mars is –5.7 °C (22 °F), while the average nighttime temperature is –79 °C (–109 °F). This daily variation in temperature is much larger than what we experience on Earth. What factor plays the largest role in this wide temperature variation, the composition or the density of the atmosphere?

Verified step by step guidance
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Step 1: Understand the composition of Mars' atmosphere. Mars' atmosphere is composed of 96% CO2, which is a greenhouse gas. However, the overall atmospheric pressure is very low, approximately 6 * 10⁻³ atm.
Step 2: Consider the role of greenhouse gases. On Earth, greenhouse gases like CO2 trap heat and help maintain a stable temperature. However, the effectiveness of this process depends on the density and pressure of the atmosphere.
Step 3: Analyze the density of Mars' atmosphere. Despite the high percentage of CO2, the low atmospheric pressure on Mars means there is not enough gas to effectively trap heat, leading to significant temperature fluctuations.
Step 4: Compare with Earth's atmosphere. Earth's atmosphere has a higher pressure and density, allowing greenhouse gases to trap more heat and reduce temperature variations between day and night.
Step 5: Conclude the primary factor. The low density and pressure of Mars' atmosphere play the largest role in the wide temperature variation, as there is insufficient atmospheric mass to retain heat effectively.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Atmospheric Composition

The composition of an atmosphere refers to the types and amounts of gases present. On Mars, the atmosphere is predominantly carbon dioxide (96%), which has different thermal properties compared to Earth's nitrogen-oxygen-rich atmosphere. This composition affects how heat is absorbed and retained, influencing temperature variations. Understanding the role of specific gases in heat retention is crucial for analyzing temperature fluctuations.
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Atmospheric Density

Atmospheric density is the mass of air per unit volume and is influenced by both temperature and pressure. Mars has a much thinner atmosphere (about 0.6% of Earth's), leading to lower density. This reduced density means that there are fewer air molecules to retain heat, resulting in significant temperature drops at night. The relationship between density and temperature variation is essential for understanding Martian climate dynamics.
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Thermal Inertia

Thermal inertia is the ability of a material to conduct and store heat. It determines how quickly a surface can heat up or cool down. On Mars, the low thermal inertia of the thin atmosphere contributes to rapid temperature changes between day and night. This concept is vital for understanding why Mars experiences such extreme temperature variations compared to Earth, where a denser atmosphere moderates temperature changes.
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Related Practice
Textbook Question

Alcohol-based fuels for automobiles lead to the production of formaldehyde (CH2O) in exhaust gases. Formaldehyde undergoes photodissociation, which contributes to photo- chemical smog: CH2O + hn ¡ CHO + H The maximum wavelength of light that can cause this reac- tion is 335 nm. (d) Write out the formaldehyde photodis- sociation reaction, showing Lewis-dot structures.

Textbook Question

An important reaction in the formation of photochemical smog is the photodissociation of NO : NO2 + hv → NO(g) + O(g) The maximum wavelength of light that can cause this reac- tion is 420 nm. (a) In what part of the electromagnetic spec- trum is light with this wavelength found?

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Textbook Question

An important reaction in the formation of photochemical smog is the photodissociation of NO : NO2 + hv → NO(g) + O(g) The maximum wavelength of light that can cause this reaction is 420 nm. (b) What is the maximum strength of a bond, in kJ/mol, that can be broken by absorption of a photon of 420-nm light?

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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Textbook Question

Phosphorus is present in seawater to the extent of 0.07 ppm by mass. Assuming that the phosphorus is present as dihydrogenphosphate, H2PO4-, calculate the correspond-ing molar concentration of H2PO4- in seawater.

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