You mix 200. mL of 0.400M HCl with 200. mL of 0.400M NaOH in a coffee cup calorimeter. The temperature of the solution goes from 25.10°C to 27.78° C. What is the molar enthalpy of neutralization of the acid in kJ/mol? Assume all densities are 1.00 g/mL and the specific heat capacities are 4.184 J/g*K.

Respuesta :

Answer : The enthalpy of neutralization is, 56.012 kJ/mole

Explanation :

First we have to calculate the moles of HCl and NaOH.

[tex]\text{Moles of HCl}=\text{Concentration of HCl}\times \text{Volume of solution}=0.400mole/L\times 0.200L=0.08mol[/tex]

[tex]\text{Moles of NaOH}=\text{Concentration of NaOH}\times \text{Volume of solution}=0.400mole/L\times 0.200L=0.08mol[/tex]

The balanced chemical reaction will be,

[tex]HCl+NaOH\rightarrow NaCl+H_2O[/tex]

From the balanced reaction we conclude that,

As, 1 mole of HCl neutralizes by 1 mole of NaOH

So, 0.08 mole of HCl neutralizes by 0.08 mole of NaOH

Thus, the number of neutralized moles = 0.08 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 = [tex]200mL+200L=400mL[/tex]

[tex]\text{Mass of water}=\text{Density of water}\times \text{Volume of water}=1g/ml\times 400mL=400g[/tex]

Now we have to calculate the heat absorbed during the reaction.

[tex]q=m\times c\times (T_{final}-T_{initial})[/tex]

where,

q = heat absorbed = ?

[tex]c[/tex] = specific heat of water = [tex]4.18J/g^oC[/tex]

m = mass of water = 400 g

[tex]T_{final}[/tex] = final temperature of water = [tex]27.78^oC=273+25.10=300.78K[/tex]

[tex]T_{initial}[/tex] = initial temperature of metal = [tex]25.10^oC=273+27.78=298.1K[/tex]

Now put all the given values in the above formula, we get:

[tex]q=400g\times 4.18J/g^oC\times (300.78-298.1)K[/tex]

[tex]q=4480.96J[/tex]

Thus, the heat released during the neutralization = -4480.96 J

Now we have to calculate the enthalpy of neutralization.

[tex]\Delta H=\frac{q}{n}[/tex]

where,

[tex]\Delta H[/tex] = enthalpy of neutralization = ?

q = heat released = -4480.96 J

n = number of moles used in neutralization = 0.08 mole

[tex]\Delta H=\frac{-4480.96J}{0.08mole}=-56012J/mole=-56.012kJ/mol[/tex]

The negative sign indicate the heat released during the reaction.

Therefore, the enthalpy of neutralization is, 56.012 kJ/mole

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