How much heat is produced when 100mL of 0.25 M HCl (Density 1.00g/mL) and 200 mL of 0.150 M NaOH (Densty 1.00g/mL) are mixed?
HCl + NaOH ? NaCl + H2O Ho298= -58kJ
If both solutions are the same temperatureand heat capaciy of the products is 4.19 j/gC, how much will the temperature increase? What assumption did you make in your calculation?

Respuesta :

Explanation:

The given data is as follows.

For HCl : Volume = 100 mL,  Density = 1.00 g/ml,  Molarity = 0.25 M

For NaOH : Volume = 200 mL,  Density = 1.00 g/ml,  Molarity = 0.150 M

Therefore, mass of HCl will be calculated as follows.

              Density = [tex]\frac{mass}{volume}[/tex]

                 1.00 g/ml = [tex]\frac{mass}{100 mL}[/tex]

                              mass = 100 g

Also, number of moles = [tex]Molarity \times Volume[/tex]

Hence, no. of moles of HCl = [tex]0.25 M \times 0.001 L[/tex]    (as 1 ml = 1000 L)

                                              = [tex]0.25 \times 10^{-3} mol[/tex]

On the other hand, mass of NaOH will be calculated as follows.

                 Density = [tex]\frac{mass}{volume}[/tex]

                 1.00 g/ml = [tex]\frac{mass}{200 mL}[/tex]

                              mass = 200 g

Also, number of moles = [tex]Molarity \times Volume[/tex]

Hence, no. of moles of HCl = [tex]0.150 M \times 0.002 L[/tex]    (as 1 ml = 1000 L)

                                              = [tex]0.3 \times 10^{-3} mol[/tex]

Total mass = (100 g + 200 g) = 300 g

Since, HCl is the limiting reagent over here. So, heat produced by [tex]0.25 \times 10^{-3} mol[/tex] will be calculated as follows.

         Q = [tex]0.25 \times 10^{-3} mol \times \Delta H^{o}_{298}[/tex]

              = [tex]0.25 \times 10^{-3} mol \times -58 kJ[/tex]

               = [tex]14.5 \times 10^{-3}[/tex] kJ

               =  [tex]14.5 \times 10^{-3} \times 10^{3}[/tex] J

Also, it is known that relation between Q and temperature change is:

                                Q = [tex]mC \Delta T[/tex]

Hence, putting the values into the above formula as follows.

                      Q = [tex]mC \Delta T[/tex]

      14.5 J = [tex]300 g \times 4.19 J/g ^{o}C \times \Delta T[/tex]      

                    [tex]\Delta T[/tex] = [tex]0.0115 ^{o}C[/tex]              

Thus, we can conclude that increase in temperature is [tex]0.0115 ^{o}C[/tex].