When a 6.50-g sample of solid sodium hydroxide dissolve in 100.0 g

When a 6.50-g sample of solid sodium hydroxide dissolve in 100.0 g of water in a coffee-cup calorimeter, the temperature rises from 21.6 C to 37.8 C. Calculate Delta H (in kJ/mol NaOH) for the solution process

    NaOH(s) ---> Na+(aq) + OH-(aq)

Assume that the specific heat of the solution is the same as that of pure water.

2 Answers

  • DeltaH = m C DeltaT

    m = 106.5 g

    C = 4.18 J/(g.K)

    DeltaT = 37.8 - 21.6 = 16.2 C = 16.2 K

    6.5 g NaOH = 0.1625 mol NaOH

    So DeltaH = (106.5 g) . (4.18 J/(g.K)) . (16.2 K) = 7.211754 kJ

    Now: 7.211754 kJ / 0.1625 mol NaOH = 44.4 (kJ/mol NaOH)

  • answer is -44.4

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