What is the molar heat of combustion for ethanol?

[bada man]

The question i am stuck on is "If 2.9g of ethanol burn with the evolution of 87 kj of heat, what is the molar heat of combustion of ethanol?" thank you for your help if it possible you can tell me how to do this question.

 

[Borek]

2.9g ethanol - how many moles?

 

[bada man]

so basically so find how many moles of ethanol in 2.9g

So u do, 2.9g/46 (46 being the molar mass of ethanol)

 

[Borek]

87 kJ for 2.9/46 moles, how much for 1 mole?

 

[LudusRex]

The molar heat of combustion for ethanol can be calculated using the given information. First, we need to convert the mass of ethanol from grams to moles. Since the molar mass of ethanol is 46.07 g/mol, we can divide the given mass of 2.9g by the molar mass to get 0.063 moles of ethanol.

Next, we can use the equation q = nΔH to calculate the molar heat of combustion, where q is the heat released, n is the number of moles, and ΔH is the molar heat of combustion.

Substituting the given values, we get:

87 kJ = (0.063 mol)ΔH

Solving for ΔH, we get a molar heat of combustion of approximately 1381 kJ/mol for ethanol.

To verify this result, we can also use the balanced chemical equation for the combustion of ethanol:

C2H5OH + 3O2 -> 2CO2 + 3H2O

According to this equation, for every 2 moles of ethanol combusted, 1381 kJ of heat is released. This supports our calculated value of 1381 kJ/mol for the molar heat of combustion of ethanol.

I hope this helps in solving the question. Remember to always use proper units and check your calculations for accuracy.