Question

10) (10pts) A cold pack consists of a small inner bag that contains water inside another larger bag that contains solid ammonium nitrate. When a cold pack is needed, the inner bag is broken and the water and ammonium nitrate are shaken together to dissolve the solid. If the inner bag contains 117 mL of water (density 1.00 g/mL), how many grams of ammonium nitrate must the outer bag contain to lower the temperature of the water from 23.0 °C to 5.0 °C? Neglect the contribution of the ammonium nitrate to both the mass and the specific heat of the water (these effects cancel each other) and the heat capacity of the plastic bag. NH4NO3 (s) + H2O(1) ► NH4+ (aq) + NO3(aq) AH= 25.69 kJ/mol

Answer 1

Given that AH = 25.69 kJ/mol - die when I mole of NHINO2 is dissolved , 25.69 kJ of heat is evolved. I mole of NH4NO3=80.043 g lie molar man of NHINO = 80.043 g mol' heat Gracity of cocter c = 4.186 J/gºc heat released in bringing the temperature of water from 23% to sc q= mass of water x cx (23°c-5°c) = 117 9 x 4.186 5/90 (18°c) q= 8815.716 J 8815.7165 No. of moles of NHA nez required = title = 25.69Kfmoi! = 0.343157 mo! - weight of NHANO required = 0.343157 molx 80.043g mol = 27.467g required. q