If 8.00 g ammonium nitrate is dissolved in 1.0 l water, the water decreases in temperature from 21.0 °c to 20.39 °c. determine the molar heat of solution (in kj/mol) of the ammonium nitrate. the density of water is 1.0 g/ml and assume that the resulting solution has the same specific heat as water (4.184 j/goc).

When Heat of solution ΔH solution = m. C.ΔT

when m is the mass of solution = mass of water + mass of ammonium nitrate

mass of water = Volume * density = 1L * 1000 g/L = 1000 g

by substitution:

m of solution = 1000 g + 8 g = 1008 g

ΔT = 21°C - 20.39 °C = 0.61°C

C = 4.184 J / g. C°

by substitution in ΔH formula:

ΔH = 1008 * 4.184 * 0.61 = 2572.7 J / 1000 = 2.57KJ

∴ molar heat of solution = heat of solution / no of mol of solute

no of moles of solute (NH4NO3) = weight / molecular weight = 8g / 80 g/mol

= 0.1 mol

∴molar heat of solution = 2.57KJ / 0.1 mol

= 25.7 KJ/mol