504 Scientific Proceedings, Royal Dublin Society. 
6. Find the heat of formation of hydrocyanic acid from its 
heat of combustion 
é[2HCON + 50 = H,0 + 200, + N.] = 316K’. 
— 2EHON - 5€0 + €H.O + 2€CO, + EN, = 316K°. 
—-316+69 +1886+0 = 25H ON. 
EHON = 29:2K™. 
7. Find the heat of formation of dilute sulphuric acid from 
the following data :— 
ESO, =76°8, éHCl = 39:3, AJel(O) = @Y), 
73°9. 
ll 
E[SO; = Cl, + 2H.0 = FSO, + 2HCl] 
~ ESO; - ECL, - 26H.0 + EHSO, - 2éHCl = (3°), 
EH:S0, = + &SO, + €Cl, + 2EH.O -— 2EHCl + 73:9 
= 76°38 + 0 + 138 -786 + 73:9 
= DPI. 
For the heat of formation of pure sulphuric acid we have 
& (H2S80.) = INC, 
EH,SO, = EH.80; + & (HS80,) 
= 21071 - 17 
= Ilsrile 
8. Given the heat of formation of hydrochloric acid, the heat of 
solution of chlorine, the heat of neutralization of hydrochloric acid 
and hydriodic acid by caustic potash, and the heat of substitution 
of iodine by chlorine in iodide of potassium: find the heat of 
formation of hydriodic acid in solution 
GEICH = 139555) 9 Cl— Wor 
