A scientist measures the standard enthalpy change for the following reaction to be -888.2 kJ :

2NH₃(g) + 3 N₂O(g)http://cxp.cengage.com/contentservic...mage/Arrow.gif4N₂(g) + 3 H₂O(g)

Based on this value and the standard enthalpies of formation for the other substances, the standard enthalpy of formation of N₂O(g) is

Ca(OH)₂(aq) + 2 HCl(aq)http://cxp.cengage.com/contentservic...mage/Arrow.gifCaCl₂(s) + 2 H₂O(l)

Based on this value and the standard enthalpies of formation for the other substances, the standard enthalpy of formation of H₂O(l) is

A scientist measures the standard enthalpy change for the following reaction to be -51.0 kJ:

Ca(OH)₂(aq) + 2 HCl(aq)http://cxp.cengage.com/contentservic...mage/Arrow.gifCaCl₂(s) + 2 H₂O(l)

Based on this value and the standard enthalpies of formation for the other substances, the standard enthalpy of formation of H₂O(l) is

A scientist measures the standard enthalpy change for the following reaction to be 154.4 kJ :

CaCO₃(s)http://cxp.cengage.com/contentservic...mage/Arrow.gifCaO(s) + CO₂(g)

Based on this value and the standard enthalpies of formation for the other substances, the standard enthalpy of formation of CaO(s) is

A scientist measures the standard enthalpy change for the following reaction to be 154.4 kJ :
CaCO₃(s)http://cxp.cengage.com/contentservic...mage/Arrow.gifCaO(s) + CO₂(g)

Based on this value and the standard enthalpies of formation for the other substances, the standard enthalpy of formation of CaO(s) is

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Originally Posted by Curlyben

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[IMG]file:///C:\Users\Safron\AppData\Local\Temp\msohtmlclip1\01 \clip_image001.gif[/IMG]H°_rxn = (2 mol)[IMG]file:///C:\Users\Safron\AppData\Local\Temp\msohtmlclip1\01 \clip_image001.gif[/IMG]H°_f(CO₂(g)) + (1 mol)[IMG]file:///C:\Users\Safron\AppData\Local\Temp\msohtmlclip1\01 \clip_image001.gif[/IMG]H°H°_f(N₂(g))(N₂(g)) - [(2 mol)[IMG]file:///C:\Users\Safron\AppData\Local\Temp\msohtmlclip1\01 \clip_image001.gif[/IMG]H°_f(CO(g)) + (2 mol)[IMG]file:///C:\Users\Safron\AppData\Local\Temp\msohtmlclip1\01 \clip_image001.gif[/IMG]H°H°_f(NO(g))](NO(g))] = -780.8 kJ

Solve for[IMG]file:///C:\Users\Safron\AppData\Local\Temp\msohtmlclip1\01 \clip_image001.gif[/IMG]H°_f(CO₂(g)) in the above equation:
[IMG]file:///C:\Users\Safron\AppData\Local\Temp\msohtmlclip1\01 \clip_image001.gif[/IMG]H°_f(CO₂(g)) = [[IMG]file:///C:\Users\Safron\AppData\Local\Temp\msohtmlclip1\01 \clip_image001.gif[/IMG]H°_rxn - (1 mol)[IMG]file:///C:\Users\Safron\AppData\Local\Temp\msohtmlclip1\01 \clip_image001.gif[/IMG]H°H°_f(N₂(g))(N₂(g)) + (2 mol)[IMG]file:///C:\Users\Safron\AppData\Local\Temp\msohtmlclip1\01 \clip_image001.gif[/IMG]H°_f(CO(g)) + (2 mol)[IMG]file:///C:\Users\Safron\AppData\Local\Temp\msohtmlclip1\01 \clip_image001.gif[/IMG]H°H°_f(NO(g))](NO(g))] / (2 mol)

= [(-780.8 kJ) - (1 mol)(0.0 kJ/mol) + (2 mol)(-110.5 kJ/mol) + (2 mol)(90.3 kJ/mol)]/(2 mol)
= -410.6 kJ/mol