ANSWER
EXPLANATION
Given that
The energy released by the system is 12.4J
Work done on the surrounding is 4.2J
Follow the steps below to find the change in energy
In the given data, energy is said to be released to the surroundings
Recall, that exothermic reaction is a type of reaction in which heat is released to the surroundings. Hence, change in enthalpy is negative
Step 1; Write the formula for calculating change in energy

Since heat is released to the surrounding, then q = -12J
Recall, that work done by the system on the surroundings is always negative
Hence, w = -4.2J
Step 2; Substitute the given data into the formula in step 1

Therefore, the change i
Soap is the sodium or potassium salt of long chain of fatty acid. Fatty acids when treated with NaOH or KOH forms Soap. This process is called as Saponification. Examples of Soap are as follow,
1. Sodium Stearate C₁₇H₃₅COONa
2. Potassium Oleate C₁₇H₃₃COOK
Reaction of Soap with MgCl₂;
When Soap is treated with MgCl₂ or CaCl₂ it forms insoluble precipitate called S.C.U.M. The reactions with MgCl₂ are as follow,
2C₁₇H₃₅COONa + MgCl₂ --------> 2C₁₇H₃₅COOMg + 2 NaCl
2C₁₇H₃₃COOK + MgCl₂ --------> 2C₁₇H₃₅COOMg + 2 KCl
These reaction are often found in hard water. And this reaction decreases the effectiveness of soap.
4 Quantum numbers are used
1.Azimuthal
2.Principal
3.Spin
4.Magnetic
Answer : The correct option is (c) 
Explanation :
The given balanced chemical reaction is,

From the balanced chemical reaction, we conclude that
As, 3 moles of
react to give 2 mole of 
So, 1 mole of
react to give
moles of 
Thus, the conversion factor needed to convert the number of moles of
to the number of moles of
produced is 
Hence, the correct option is (c) 