How do I do 2 and 3 2 Calculate the enthalpy H gained or los

How do I do 2 and 3

2. Calculate the enthalpy (H) gained or lost for each of the following. a 214g NaOH are dissolved in water b.35 mol H,O freezes c. 25.3 cm of ice melts (note: you must first d d 1003 g ethanol (C H.OH) evaporates etermine, via research, the density of ice to get its mass) 3. For cach of the occurrences in problem 2, above, indicate whether the heat change is exothermic (H) or endothermic (H):

Solution

2a Enthalpy change when one mole(40g) NaOH dissolved in water=-45.7Kj/mol

Enthalpy changes when 21.4g NaOH dissolves in water is =-45.7/40*21.4= -24.5Kj

2b Enthalpy changes when 18g water freezes = 6.01kj/mol

Enthaplpy changes when 3.5 moles of water freezes =3.5*6.01=21.03Kj

2 c) Density of ice = 0.91g/ml

Mass of ice taken =0.91*25.3= 23.02g

Enthalpy changes when 23.02g ice melt is = 23.01*(-6.01)/18= -7.68kj

2d Enthalpy of vaporisation of 1mol ethanol=39.3Kj/mol

Enthalpy changes when 100.5g ethanol evaporate =39.3/46.7*100.5=84.57kj

3) If heat change is negative than exothermic reaction André if heat change is postive than endothermic reaction

a for this reaction heat change is negative so exothermic reaction

b) heat change is negative so exothermic reaction

c) heat changes is positive so endothermic reaction

d) heat change is positive so endothermic reaction