[adiabatic]

Consider the reaction (assume 300 K initial temp. of reactants)

CH4 + 2O2 --> CO2 + 2H2O

the Enthalpy of combustion of methane is Delta H = -889kJ/mole

Given that the heat capacities as gases are as follows:
CH4: 35.6 J/mole K (at 300 K)
O2: 29.3 J/mole K (at 300 K)
CO2 62.4 J/mole K (high temp. limit)
H2O 58.2 J/mole K (high temp. limit)

******Calculate the sum of the heat stored in the reactants (at 300 K) and the heat released in the reaction as written.******

******Calculate the theoretical adiabatic flame temperature******

[Borek]

You have to show your attempts at solving the question to receive help. This is a forum policy.

[Enthalpy]

Bizarre wording anyway.

With pure oxygen, the reaction won't produce CO₂ nor be complete. Expect CO, O₂, H₂ and many radicals, in proportions depending much on the temperature.

The heat capacity of CO₂ and H₂O are given arbitrarily as 7.5*R and 7.0*R but measured values differ and not little.

It would also be useful to know if methane's heat of combustion is measured at 300K and if the resulting H₂O is liquid.

The "heat stored in the reactants" makes little sense because the heat capacity changes so much at cold. The text should tell if this is an integral heat capacity measured from zero to 300K - including all phase changes in case the pressure isn't vanishingly small. Instead of following the hints, I'd feel more sensible to compute the final temperature starting from 300K, especially if (as is usual) the heat of combustion is measured at 300K.

[KarinBergling]

I have a quite similar problem!

I need to calculate the heat evolved or absorbed when 10g of Nacl is dissolved in 100g of water.  I know that the enthalpi of solution is 3.9 kJ/mole NaCl and that the specific heat capacity of the solution is 4.18J/(K×g). There is nothing said about temperatures

I really dont know where to start with this problem, I have the formula C=q/deltaT

Do you have any ideas?

[Corribus]

Enthalpy of solution is the amount of heat absorbed or released when 1 mole of the substance is dissolved in an "infinite" amount of solvent (i.e., in the limit of very low concentration). Does this definition help you?

[KarinBergling]

That definition will definetly help me! Thanks!

[Borek]

Enthalpy of solution is the amount of heat absorbed or released when 1 mole of the substance is dissolved in an "infinite" amount of solvent (i.e., in the limit of very low concentration).

Isn't it a definition of a "specific enthalpy of solution"?

[Corribus]

Yes, sorry, I felt that was understood.

[KarinBergling]

Whats the difference?  Between specific entalpy of solution and entalpy of solution?

[Corribus]

Basically, one is an extensive property (does not depend on the amount or size of the system) and the other isn't.