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Calculate the change in enthalpy for the chemical reaction N2(g) + 3H2(g) --> 2NH3(g)
Δ H = Bonds Broken - Bonds Formed
The coffee cup calorimeter is used to calculate heat flow so that mean pressure needs to remain constant.
Enthalpy of Combustion: Product - Reactant
Product: (2 * -393.5) + ( 3 * -285.8) = -1644.4
Reactant: ( -84.7 )
Enthalpy of Combustion: -1644.4 + ( -84.7) = -1559.7
The following question is from the ACS Study Guide. It would be better to ask which diagram best represents the change in enthalpy for the dissolution process.
The dissolution process - where solid, liquid, gas particles are broken into solutes. To break apart molecules from each other requires energy therefore this is an endothermic reaction as shown in graph A.
q(alloy) = q(water)
Only 1 mole of the compound is formed from its constituent elements. Therefore, the first option is right.
ΔH reaction = Product - Reactant
Freezing a liquid requires energy to be removed so it is an exothermic process. Melting requires adding energy so it is an endothermic process.
Heat of Vaporization is 40.7 kJ/mol
2 H2O2 ---> 2H2 + 2 O2 ΔH = 376
2H2 + O2 ----> 2H2O ΔH = -572
2H2O ---> O2 + 2H2O ΔH =-196
When 192 J of energy are added to a sample of gallium that is initially at 25.0 oC, the temperature rises to 35.0 oC. What is the volume of the sample in cubic centimeter?
q = 192 J
q = mC ΔT
m = q / (C ΔT)
m = 192 / ( 0.372 x 10) = 51.6 g
51.6 g x ( 1cm^3/ 5.904 g) = 8.74 cm 3