Question

[1] Mass of salt (g) 2.005 1.993 [2] Volume of DI water (mL) 49.8 50.0 Mass of DI water (g) [3] Temperature of DI water (°C) 23.4 23.5 [4] Temperature of mixture after dissolution (°C) 20.4 30.9 Temperature difference (°C) -3 7.4 [5] Total mass in reaction (g) 2.1 2.0 Total moles reacted (mol) .026 Total heat of the reaction (cal) [6] Enthalpy of solution ΔHsolution (cal/mol)

Answer 1

The reaction between hydrogen ion and hydroxide ion will be as follows.

       

so, ratio between hydrogen and hydroxide ions is 1 : 1.

Therefore, moles of  = volume × concentration of

                            =

                             = 0.06 mol

Similarly, moles of  = volume × concentration of

                              =

                             = 0.1 mol

Therefore, ratio of moles of hydrogen and hydroxide ions is as follows.

                                    0.06 : 0.1

                                 = 0.6 : 1

As, hydroxide ions are present in excess so, hydrogen ions are the limiting reagent.

Hence, moles of water formed = moles of  ions = 0.06 mol.

So,    heat released = moles of

                               = 0.062 × 62.0 kJ/mol

                               = 3.72 kJ

                               = 3.72 × 1000 J

                               = 3720 J

Let T is the initial temperature. So,

             Heat released = Heat absorbed by the solution

                                      =

           3720 J =

                         T =

Thus, we can conclude that initial temperature is .