lecture6

When the reaction is ignited the temperature rises

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: = qP Example: A bomb calorimeter with a heat capacity of 476 J/K is charged with 0.5173 g of ethanol (C2H5OH) and excess O2 and immersed in a insulated tank containing 740 g of water. When the reaction is ignited, the temperature rises from 25.000° C to 29.289° C. Calculate ∆E for the reaction C2H5OH + 3 O2 Æ 2 CO2 + 3 H2 O heat released by the reaction = heat absorbed by the water and the bomb q = sm∆T + C∆T = (4.184 J/gK)(740 g)(4.289 K) + (476 J/K)(4.289 K) = 15.3 kJ 15.3kJ 46.07 g q(rxn) = x = -1,364 kJ 0.5173 g 1 mole 6-4 Chapter 6 Thermochemistry 6.3 Hess's Law Enthalpy is a function of state, so for a reaction A Æ B ∆H1 = HB - HA B Æ A ∆Hrev = HA - HB ∆Hrev = -∆Hfor ∆H is an extensive property (depends on amount) so for 2A Æ 2B, ∆H2 = 2∆H1 Hess’ Law: When a process is considered as a sequence of steps, the enthalpy change for the overall process is equal to the sum of the ∆H values for each individual step. C(graphite) + O2(g) Æ CO2(g) ∆H = -393.5 kJ C(diamond) + O2(g) Æ CO2(g) ∆H = -395.4 kJ Calculate ∆H for the reaction C(graphite) Æ C(diamond) C(graphite) + O2(g) Æ CO2(g) ∆H = -393.5 kJ CO2(g) Æ C(d...
View Full Document

This note was uploaded on 04/05/2014 for the course CHEM 1211 taught by Professor Jackduff during the Spring '13 term at SPSU.

Ask a homework question - tutors are online