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Environmental Chemistry

Multiple Choice Questions

31.

The pair of gases responsible for acid rain are

H₂, O₃
CH₄, O₃
NO₂, SO₂
CO, CH₄

32.

Cataract and skin cancer are caused by

depletion of nitric oxide
depletion of ozone layer
increase in methane
depletion of nitrous oxide

33.

On the top of mountain, water boils at

high temperature
same temperature
high pressure
low temperature

34.
What are X and Y in the following reaction?
${CF}_{2} {Cl}_{2} \overset{UV}{\to} X + Y$

CF₂Cl, Cl

C₂F₄, Cl₂

CFCl₂, F

CCl₂, F₂

CF₂Cl, Cl

Since, chlorofluorocarbon compounds, i.e , freons (CFCs) are non-reactive, non-inflamable, non-toxic organic molecules, these are widely used in air conditioner, refrigerators, in electronic industry for cleaning computer parts. Due to very long life time (CF₂Cl₂-12 '139 years, CFCl₃-11 77 years), these compounds ultimately react the stratosphere where they get broken down by powerful UV radiations and release chlorine free radical. The chlorine free radicals react with ozone and cause its depletion.

${CF}_{2} {Cl}_{2} \overset{hv}{\to} \overset{\cdot}{C} l + \overset{\cdot}{C} F_{2} Cl {CFCl}_{3} \overset{hv}{\to} \overset{\cdot}{C} l + \overset{\cdot}{C} F_{2} Cl Hence, x + y = \overset{\cdot}{C} l + \overset{\cdot}{C} F_{2} Cl$