A student added 5.350 g of ammonium chloride to 100.00 cm3 of water. the initial temperature of the water was 25.55℃ but it decreased to 21.79℃. calculate the enthalpy change that would occur when 1 mol of the solute is added to 1.0000 dm3 of water.

Question

Chemistry

Zack

23 March, 11:07

A student added 5.350 g of ammonium chloride to 100.00 cm3 of water. the initial temperature of the water was 25.55℃ but it decreased to 21.79℃. calculate the enthalpy change that would occur when 1 mol of the solute is added to 1.0000 dm3 of water.

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Julie Bridges · Answer 1

Answer is: 16,56 kJ.

1) m (NH₄Cl) = 5,35g.

m (H₂O) = d (H₂O) · V (H₂O) = 1g/cm³ · 100cm³ = 100g.

ΔT = 25,55°C - 21,79°C = 3,76°C.

Q = m (solution) · C (specific heat capacity of water) ·ΔT.

Q = 105,35g · 4,18 J/g·°C · 3,76°C = 1655,76J.

2) m (NH₄Cl) = 1mol · 53,5g/mol = 53,5g.

m (water) = d (H₂O) · V (H₂O) = 1g/cm³ · 1000cm³ = 1000g.

m (solution) = 1053,5g, ten times more than first solutn.

Q = 10 · 1655,76J = 16557,6J = 16,56 kJ.