Notes 111709

# Notes 111709 - Coffee Cup calorimeter Closed System at...

This preview shows pages 1–3. Sign up to view the full content.

Coffee Cup calorimeter Closed System- at constant pressure, all of the heat from the process goes into the water, q h2o = -q process The specific heat of water is 4.182 J/gram K H = E + PV PV = nrt But for some chemical reactions we have: Delta H = Delta E + delta-n * RT where Delta n = n final –n initial If there is no net change in # of moles of gas then Delta H = Delta E Consider this reaction at 200 deg. C 2 NO + O2 2 NO2 Delta H – Delta E Delta n = 2 – 3 = -1 Delta-n * RT = (-1 mol ) (8.314 J/K mol) (473 K) Delta-n * RT = -3932 J = -3.93 kJ Delta H of a Reaction Tells how much energy is released/absorbed for the quantities as written in the equation: CH 4 + 2 O2 CO2 + 2H2O Delta H = -890 kJ

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Heat of Combustion – Example How much heat is absorbed or evolved when 16 g of O2 is reacted according to the reaction? SiH4 + 2 O2 SiO2 + 2H2O Delta H = -1515.7 kj/mol rxn 16 g / 32 g / mol = ½ mol of O2 Note 2 moles of O2 are required per mol-rxn Delta H for 16 g O2 = ¼ mol rxn (-1515.7 kj/mol rxn)
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 4

Notes 111709 - Coffee Cup calorimeter Closed System at...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online