Use M1V1 = M2V2 to solve
3(V1) = 2.8 * 1.6
3(V1) = 4.48
V1 = 1.493 L of stock solution
1.05moles
Explanation:
Given parameters:
Number of molecules of C₂H₆ = 6.29 x 10²³molecules
Unknown:
Number of moles = ?
Solution:
The mole is the amount of substances that contains Avogadro's number of particles i.e 6.02 x 10²³
To find the number of moles:
number of moles = 
number of moles = 
number of moles = 1.05moles
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Energy= 2381 joules
heat= Mass(kg) *change in temperature(K) * Cp
2381=0.155*(15)*Cp
Cp=1024 J/kg K
Answer : The correct option is, (b) +115 J/mol.K
Explanation :
Formula used :

where,
= change in entropy
= change in enthalpy of vaporization = 40.5 kJ/mol
= boiling point temperature = 352 K
Now put all the given values in the above formula, we get:



Therefore, the standard entropy of vaporization of ethanol at its boiling point is +115 J/mol.K