1. Calculate heat change,q, using equation: q = mass* C * ∆T
• given that volume = 230ml ,therefore mass of water = 230g
,
• ∆T = Tfinal-Tinitial =30.5-22.9 = 7.6°C
,
• Specific heat capacity of water , C= 4.184J/°C*g
• Therefore , q = mass* C * ∆T
= 230 * 4.184 * 7.6
=7313.6 J /1000
q= 7.314KJ
2. Calculate Molar enthalpy using ∆H = q/n
• given : mass of methanol burned = Mass F-Mass initial
=(2.51-1.65) = 0.86 g
• So ,moles of methanol , n = mass methanol/Mol. mass methanol
= 0.86g/32.04g/mol
=0.027 moles
• Finally , ∆H = q/n
= 7.314KJ / 0.027mol
=270.85KJ/mol
• However, this is an exorthemic reaction, heat is lost through combustion, our molar enthalpy should be negative.
This means that ∆H= -270.85KJ/mol