A 4.305-g sample of a nonelectrolyte is dissolved in 105 g of water. the solution freezes at -1.23c. calculate the molar mass of
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Answer : The correct option is, (A) -101.37 KJ
Explanation :
First we have to calculate the moles of HCl and NaOH.
The balanced chemical reaction will be,
From the balanced reaction we conclude that,
As, 1 mole of HCl neutralizes by 1 mole of NaOH
So, 0.1392 mole of HCl neutralizes by 0.1392 mole of NaOH
Thus, the number of neutralized moles = 0.1392 mole
Now we have to calculate the mass of water.
As we know that the density of water is 1 g/ml. So, the mass of water will be:
The volume of water =
Now we have to calculate the heat absorbed during the reaction.
where,
q = heat absorbed = ?
= specific heat of water =
m = mass of water = 174 g
= final temperature of water = 317.4 K
= initial temperature of metal = 298 K
Now put all the given values in the above formula, we get:
Thus, the heat released during the neutralization = -14.11 KJ
Now we have to calculate the enthalpy of neutralization.
where,
= enthalpy of neutralization = ?
q = heat released = -14.11 KJ
n = number of moles used in neutralization = 0.1392 mole
Therefore, the enthalpy of neutralization is, -101.37 KJ