Solve CCl3F & CCl2F2 Molar Concentration in Tropo/Stratosphere

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In summary, the gases CCl3F and CCl2F2 are linked to ozone depletion in Antarctica and were found in quantities of 261 and 509 parts per trillion by volume in 1994. To compute the molar concentration of these gases under different conditions, we can use the ideal gas equation and the definition of ppt (1 part per trillion = 1 molecule per trillion molecules). By calculating the number of moles of air in a volume of 1 liter under the given conditions, we can determine the number of moles of the CFCs present and thus the molar concentration.
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Thermo Question!

Homework Statement



CCl3F and CCl2F2 have been linked to ozone depletion in Antarctica. As of 1994, these gases were found in quantities of 261 and 509 parts per trillion (1012) by volume (World Resources Institute, World resources 1996–97). Compute the molar concentration of these gases under conditions typical of (a) the mid-latitude troposphere (10°C and
1.0 atm) and (b) the Antarctic stratosphere (200 K and 0.050 atm).

Homework Equations


pV=nRT


The Attempt at a Solution


Okay ppt is hurting my head. Basically ppt = 1ng/L

CCl3F MW = 137.37 g/mol

So I did (137.37 g/mol)/(251g/1x10^9L )to get mol/L

But I end up getting 0.526 nL/mol..

So when I go to plug in n = pV/RT to solve for my molecular weight concentration I don't know how the units are going to cross out... because its 0.526 nL/mol..
Can I just multiply 0.526(1x10^-9nL= to get L? Or is that against multiplication rules. I've never really dealt with ppt.
 
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Hello Workout,

Just stick to the definition of ppt given in your problem statement. 1 part per trillion is exactly what is says. It's just a RATIO. So, for every trillion molecules of air*, there is 1 molecule of the chloro-fluoro-carbon, or whatever that is (I'm not a chemist).

So what you have to do is use the ideal gas equation to compute how many moles of air you have in a volume of 1 litre under each set of atmospheric conditions. Based on that number of moles of air, you can figure out the number of moles of the CFC in question (becuase you know the ratio in ppt). This will give you, directly, the number of mol/L of the CFC.

*note: it was 1 part per trillion by volume, not by mass. Since, in a gas at a given temperature and pressure, the volume occupied is proportional to the number of particles, this means that it's one litre for every trillion litres, or equivalently, one particle for every trillion particles. In contrast, if it had been one ppt BY MASS, then it would not be one particle for every trillion particles, it would have been one gram for every trillion grams. If the substance is heavier than air, this would mean *fewer* than one particle for every trillion particles.
 

FAQ: Solve CCl3F & CCl2F2 Molar Concentration in Tropo/Stratosphere

1. What is the significance of CCl3F and CCl2F2 in the troposphere and stratosphere?

CCl3F and CCl2F2 are both types of chlorofluorocarbons (CFCs) that were commonly used as refrigerants and propellants. They are significant because they are responsible for the depletion of the ozone layer in the stratosphere.

2. How are the molar concentrations of CCl3F and CCl2F2 calculated in the troposphere and stratosphere?

The molar concentrations of CCl3F and CCl2F2 are calculated by measuring the amount of these compounds present in a given volume of air in the troposphere and stratosphere. This can be done through direct measurement or through atmospheric modeling.

3. What is the current level of molar concentration of CCl3F and CCl2F2 in the troposphere and stratosphere?

The molar concentration of CCl3F and CCl2F2 has been steadily decreasing due to international efforts to phase out the use of these compounds. As of 2021, the molar concentration of CCl3F is around 0.22 parts per billion (ppb) in the troposphere and 0.01 ppb in the stratosphere, while the molar concentration of CCl2F2 is around 0.08 ppb in the troposphere and 0.01 ppb in the stratosphere.

4. What are the potential effects of high molar concentrations of CCl3F and CCl2F2 in the troposphere and stratosphere?

High molar concentrations of CCl3F and CCl2F2 can lead to the depletion of the ozone layer in the stratosphere. This can have a range of effects, including increased levels of harmful UV radiation reaching the Earth's surface, which can have negative impacts on human health and the environment.

5. What measures are being taken to reduce the molar concentrations of CCl3F and CCl2F2 in the troposphere and stratosphere?

In 1987, the Montreal Protocol was signed by multiple countries, which aimed to phase out the production and use of CFCs, including CCl3F and CCl2F2. This has led to a decrease in molar concentrations of these compounds in the atmosphere. Additionally, alternative substances, such as hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs), are now being used as replacements for CFCs.

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