HardChemistryHigh School (11–12)Organic Compounds with Functional Groups › Haloalkanes and HaloarenesNumerical
A leak lets 1.00 kg of freon-12, CCl₂F₂ (molar mass 121.0 g/mol), reach the stratosphere…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A leak lets of freon-12, (molar mass ), reach the stratosphere. Assume, as a simple model, that both chlorine atoms of every molecule are set free by ultraviolet light, and that each chlorine atom destroys ozone molecules before it is removed. The molar mass of ozone is . Find the amount of freon-12, the amount of chlorine atoms freed and the mass of ozone that is destroyed, in tonnes. One tonne is .
Need a reminder? The key ideaShow
The percentage of an element in a compound is the mass of that element in one mole divided by the molar mass. Freons are made from tetrachloromethane and HF. DDT is made from two moles of chlorobenzene and one mole of chloral. One chlorine atom in the stratosphere destroys about ozone molecules.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Freon-12. .
Step 2. Chlorine atoms. .
Step 3. Ozone. of ozone.
Step 4. Mass. .
Answer: , and tonnes of ozone.
Check. One kilogram of a gas destroys tens of tonnes of another, because the chlorine atom is a catalyst. The real effect is smaller, since not all of the chlorine reaches the cycle.
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