Map aa Sapling Learning macmillan learning In a constant pressure calorimeter, 7

Question

Map aa Sapling Learning macmillan learning In a constant pressure calorimeter, 70.0 mL of 0.940 M H2SO4 was added to 70.0 mL of 0.320 M NaOH. The reaction caused the temperature of the solution to rise from 21.65 °C to 23.83 °C. If the solution has the same density and specific heat as water (1.00 g/mL and 4.184 J/g K, respectively), what is AH for this reaction (per mole of H20 produced)? Assume that the total volume is the sum of the individual volumes. Number kJ mol H, O AH 9.708 Previous 3 Give Up & View Solution Try Again Next Exit Explanation First, calculate the amount of heat, q, absorbed by the solution. CAT where c 4.184 J/(g. OC). The mass, m, in grams is equal to the total volume in ters because the density is 1.00 g/mL. The change in temperature is AT J final nitial The heat absorbed by the solution is equal to the heat released in the reaction, but then must be scaled per mole of H20. Thus, you'll need to determine the moles of H20 produced, keeping in mind that there may be a limiting reactant. Also pay attention to the sign of your answer. H,SO, NaOH

Explanation / Answer

moles of H2SO4 = 70 x 0.940 / 1000 = 0.0658

moles of NaOH = 70 x 0.320 / 1000 = 0.0224

total volume = 70 + 70 = 140 mL

mass of solution = 140 g

dT = 23.83 -21.65 = 2.18 oC

Q = m Cp dT

Q = 140 x 4.184 x 2.18 = 1277 J

Q = 1.277 kJ

H2SO4 + 2NaOH ----------------------> Na2SO4 + 2H2O

1                  2

0.0658      0.0224

NaOH is limiting reagent so moles of H2O formed = 0.0224

deltaH = - 1.277 kJ / 0.0224

           = - 57.0 kJ / mol

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