40.0 ml of 1.00 m koh(aq) and 40.0 ml of 0.500 m h2so4(aq) are mixed in a coffee-cup calorimeter, both at 21.00°c. the final solution has a density of 1.02 g/ml, a volume of 80.0 ml, a specific heat of 4.00 j g-1 °c -1 , and a temperature of 27.85°c. calculate the enthalpy change of this reaction per mole of h2o formed.

-56.4 kJ/mol

Explanation:

There are two heat flows in this experiment.

Heat released by reaction + heat absorbed by solution = 0

                     q1                   +                     q2                     = 0

                   nΔH                 +                  mCΔT                  = 0

1. Moles of water formed

                  KOHL + H2SO4 → K2SO4 + 2H2O

V/mL:          40.0        40.0

c/(mol/L)      1.00       0.500

   Moles of KOH = 40.0 mL × (1.00 mmoL/1 mL)     = 40.00 mmol KOH

Moles of H2SO4 = 40.0 mL × (0.500 mmoL/1 mL) = 20.00 mmol H2SO4

Moles of H2O from KOH

= 40.00 mL KOH × (2.00 mmol H2O/2 mmoL KOH)  = 40.00 mmol H2O

Moles H2O from of H2SO4

= 20.00 mL × (2 mmoL H2O/1 mmol H2SO4)             = 40.00 mmol H2O

KOH and H2SO4 are present in equimolar amounts.

They form 40.00 mmol = 0.040 00 mol of water.

2. Calculate q1

q1 = 0.04000 mol × ΔH = 0.040 00ΔH J

3. Calculate q2

Mass of water formed = 0.040 00 mol × (18.02 g/1 mol) = 0.7208 g

                  V(solution) = 40.00 + 40.00 = 80.00 mL

        Mass of solution = 80.00 mL × (1.02 g/1 mL) = 81.60 g

                 Total mass = 81.60 + 0.7208 = 82.32 g

                              ΔT = T2 - T1 = 27.85 - 21.00 = 6.85 °C

                              q2 = 82.32 × 4.00 × 6.85 = 2256 J

4. Calculate ΔH

0.040 00ΔH + 2256 = 0

            0.040 00ΔH = -2256

                           ΔH = -2256/0.040 00 = = -56 400 J/mol = -56.4 kJ/mol

The enthalpy of neutralization is -56.4 kJ/mol.

both adhesion and cohesion are attractions.

they are different in that adhesion is the force of attraction between the molecules of two different substances, whereas cohesion is the force of attraction between molecules of the same substance.

possible examples include capillary action, in which the adhesion between water and glass causes the water to rise in a narrow tube against the force of gravity.

because of hydrogen bonding, water is extremely cohesive.

this causes molecules on the surface of water to be drawn inward, which is why drops of water form beads on smooth surfaces.

hope this .

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