Answer to Enthelpy Question: Which Outputs Most Energy?

• apchemstudent
In summary, the question is asking which reaction will output the most energy per mass of the reactants. The answer is b) because the enthalpy is given in terms of moles of reaction, and it is related to the moles of fuel and oxidant, both of which are reactants. The formula for calculating energy per mass is energy/{(mass of oxidant)(mass of fuel)}, and it is in terms of mass. To determine the mass of each reactant, their atomic masses are added up, and it is found that the reaction of hydrogen and oxygen to form water gives the most energy per mass of reactants.
apchemstudent
I'm not really sure what the question is asking for. But my guess is they are asking for which one will output the most energy per mass of the reactants. If this is correct, then I am guess the answer is b). If not can some one explain why? Thanks.

Attachments

• enthalpy question.jpg
26.9 KB · Views: 458
the enthalpy is given in terms of moles of reaction, you'll need to read up on this and then relate moles of reaction to moles of the fuel (compound being oxidized) and the oxidant...basically both are reactants.

energy/{(mass of oxidant)(mass of fuel)}, note it is in terms of mass.

GCT said:
the enthalpy is given in terms of moles of reaction, you'll need to read up on this and then relate moles of reaction to moles of the fuel (compound being oxidized) and the oxidant...basically both are reactants.

energy/{(mass of oxidant)(mass of fuel)}, note it is in terms of mass.

What i did was i said the enthalpy represented change in energy/(per reaction). Although it says moles, but that doesn't really make sense since each of the reactants and products have different coefficients.

So each reaction needs a certain amount of reactants and i simply added up their atomic masses. It seems like hyrogen + 1/2 O2 -> H2O gives the most energy per mass of reactants. But I am not sure...

1. What is enthalpy and why is it important?

Enthalpy is a thermodynamic property that measures the total energy of a system. It includes both the internal energy of a system and the work required to change the system's volume. Enthalpy is important because it helps us understand and predict the behavior of chemical reactions and physical processes.

2. How is the energy output of a system measured?

The energy output of a system can be measured in different units depending on the type of system. For a chemical reaction, the energy output can be measured in joules (J) or kilojoules (kJ). For physical processes, the energy output can be measured in calories (cal) or kilocalories (kcal). Additionally, the energy output can also be measured in terms of temperature change, such as degrees Celsius (°C) or kelvin (K).

3. Which factors affect the energy output of a system?

The energy output of a system can be affected by various factors, such as the type of reaction or process, the amount of reactants or substances involved, the temperature and pressure of the system, and the presence of catalysts or inhibitors. These factors can influence the amount of energy released or absorbed during a reaction or process.

4. How does the energy output of a system relate to its enthalpy?

The energy output of a system is directly related to its enthalpy. In an exothermic reaction or process, the energy output is negative, indicating a decrease in enthalpy. This means that the system releases energy in the form of heat or light. In an endothermic reaction or process, the energy output is positive, indicating an increase in enthalpy. This means that the system absorbs energy from its surroundings.

5. Can the energy output of a system be changed?

Yes, the energy output of a system can be changed by altering the conditions of the system, such as temperature, pressure, or reactant concentrations. For example, increasing the temperature of a reaction can lead to a higher energy output as more energy is required to break and form bonds. Additionally, the use of catalysts or inhibitors can also affect the energy output of a system by changing the rate of the reaction or process.

• Chemistry
Replies
4
Views
2K
• Chemistry
Replies
7
Views
1K
• Chemistry
Replies
3
Views
1K
• Chemistry
Replies
0
Views
250
• Chemistry
Replies
5
Views
1K
• Introductory Physics Homework Help
Replies
3
Views
682
• Chemistry
Replies
7
Views
2K
• Electrical Engineering
Replies
38
Views
2K
• Chemistry
Replies
46
Views
2K
• Chemistry
Replies
4
Views
1K