How can I find the amount of heat released in an enthalpy reaction?

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In summary, heat released in enthalpy refers to the amount of thermal energy released or absorbed during a chemical reaction at constant pressure. It is measured using a calorimeter and is affected by factors such as the nature and number of reactants and products, temperature and pressure, and physical state. The sign of the enthalpy change can indicate the spontaneity of a reaction, with negative values indicating exothermic reactions and positive values indicating endothermic reactions. This information can also be used to predict the direction of a reaction, but other factors such as entropy must also be considered.
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viper2308
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Hi, new to the forum.

I need help on how to find out how much heat is released in an enthalpy reaction.

The problem is: 4 Fe(s) + 3 O2(g) 2 Fe2O3(s) Delta H = -1652 kJ
(a) How much heat is released when 4.68 mol iron is reacted with excess O2?
 
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  • #2
make a conversion factor (aka as unit factor) out of your equation

4 moles of Fe = -1652 kJ

4.68 mol of Fe = x kJ
 
  • #3


Hi there,

To find out how much heat is released in an enthalpy reaction, we can use the equation: q = m x c x delta T, where q is the heat released, m is the mass of the substance, c is the specific heat capacity, and delta T is the change in temperature. In this case, we can use the given enthalpy change (Delta H = -1652 kJ) to find the heat released.

First, we need to determine the number of moles of Fe2O3 produced in the reaction. From the balanced chemical equation, we can see that for every 4 moles of Fe reacted, 2 moles of Fe2O3 are produced. Therefore, if 4.68 mol of Fe is reacted, we can expect to produce 2.34 mol of Fe2O3.

Next, we need to calculate the heat released per mole of Fe2O3 produced. To do this, we divide the given enthalpy change by the number of moles of Fe2O3 produced: -1652 kJ / 2.34 mol = -705 kJ/mol. This means that for every mole of Fe2O3 produced, 705 kJ of heat is released.

Finally, to find the heat released when 4.68 mol of Fe is reacted, we multiply the heat released per mole by the number of moles of Fe reacted: 705 kJ/mol x 4.68 mol = 3300 kJ. Therefore, when 4.68 mol of Fe is reacted with excess O2, 3300 kJ of heat is released.

I hope this helps! Let me know if you have any further questions. Good luck!
 

1. What is heat released in enthalpy?

Heat released in enthalpy refers to the amount of thermal energy released or absorbed during a chemical reaction at constant pressure. It is a measure of the change in the internal energy of a system.

2. How is heat released in enthalpy measured?

Heat released in enthalpy is typically measured using a calorimeter, which is a device that can accurately measure the heat transferred during a reaction. This measurement is usually done at constant pressure, and the resulting value is known as the enthalpy change.

3. What factors affect the amount of heat released in enthalpy?

The amount of heat released in enthalpy is affected by several factors, including the nature and number of reactants and products, the temperature and pressure of the reaction, and the physical state of the reactants and products.

4. How does heat released in enthalpy relate to the spontaneity of a reaction?

The sign of the enthalpy change (positive or negative) can indicate the spontaneity of a reaction. A negative enthalpy change indicates that the reaction is exothermic and releases heat, making it more likely to occur spontaneously. A positive enthalpy change indicates an endothermic reaction, which requires an input of heat and is less likely to occur spontaneously.

5. Can heat released in enthalpy be used to predict the direction of a reaction?

Yes, the direction of a reaction can be predicted using the enthalpy change. In an exothermic reaction, the products have a lower enthalpy than the reactants, so the reaction will proceed in the forward direction. In an endothermic reaction, the products have a higher enthalpy, so the reaction will proceed in the reverse direction. However, other factors such as entropy also play a role in determining the direction of a reaction.

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