- Answer: <em><u>The compounds containing CFCs (chlorofluorocarbons) are mainly responsible for ozone layer depletion as these compounds react with ozone in the presence of ultraviolet rays to form oxygen molecule and thus, destroying ozone.</u></em>
Explanation: <em><u>Human activities cause the emission of halogen source gases that contain chlorine and bromine atoms. These emissions into the atmosphere ultimately lead to stratospheric ozone depletion. The source gases that contain only carbon, chlorine, and fluorine are called chlo- rofluorocarbons usually abbreviated as CFCs.</u></em>
<u>Answer:</u> The
for the reaction is -1406.8 kJ.
<u>Explanation:</u>
Hess’s law of constant heat summation states that the amount of heat absorbed or evolved in a given chemical equation remains the same whether the process occurs in one step or several steps.
According to this law, the chemical equation is treated as ordinary algebraic expressions and can be added or subtracted to yield the required equation. This means that the enthalpy change of the overall reaction is equal to the sum of the enthalpy changes of the intermediate reactions.
The chemical reaction for the formation reaction of
is:

The intermediate balanced chemical reaction are:
(1)
( × 6)
(2)
( × 3)
(3)
( × 2)
(4)

The expression for enthalpy of formation of
is,
![\Delta H^o_{formation}=[6\times \Delta H_1]+[3\times \Delta H_2]+[2\times \Delta H_3]+[1\times \Delta H_4]](https://tex.z-dn.net/?f=%5CDelta%20H%5Eo_%7Bformation%7D%3D%5B6%5Ctimes%20%5CDelta%20H_1%5D%2B%5B3%5Ctimes%20%5CDelta%20H_2%5D%2B%5B2%5Ctimes%20%5CDelta%20H_3%5D%2B%5B1%5Ctimes%20%5CDelta%20H_4%5D)
Putting values in above equation, we get:
![\Delta H^o_{formation}=[(-74.8\times 6)+(-185\times 3)+(323\times 2)+(-1049\times 1)]=-1406.8kJ](https://tex.z-dn.net/?f=%5CDelta%20H%5Eo_%7Bformation%7D%3D%5B%28-74.8%5Ctimes%206%29%2B%28-185%5Ctimes%203%29%2B%28323%5Ctimes%202%29%2B%28-1049%5Ctimes%201%29%5D%3D-1406.8kJ)
Hence, the
for the reaction is -1406.8 kJ.
<u>Answer:</u> The concentration of the solution is 0.25 M
<u>Explanation:</u>
Let the volume of solution of 2.5 M NaCl be 10 mL
We are given:
Dilution ratio = 1 : 10
So, the solution prepared will have a volume of = 
To calculate the molarity of the diluted solution, we use the equation:
where,
are the molarity and volume of the concentrated NaCl solution
are the molarity and volume of diluted NaCl solution
We are given:
Putting values in above equation, we get:

Hence, the concentration of the solution is 0.25 M