I with how to do change in enthelpy

[NickP717]

The problem says: Enthalpy is always reported with respect to a reactant. Calculate the enthalpy change, DeltaH, for each reaction in terms of kJ/mol for one of the reactants. (i.e either HCL or NaOH).

I had three reactions:

1. NaOH + HCL---->H20 +NaCl
2.NH4Cl +NaOH---->H20 +NH3 +NaCl
3. HCl +NH3---->NH4

The first reaction I measured out 25.3mL of 2.0M HCl into a foam cup, then I dumped in 25.4mL of NaOH solution into the cup... my lowest temperature was 22.6 degrees C (before two solutions re combined., and my highest was 35.7 degrees C (when the solutions were mixed).

The second reaction I measured 25mL of 2.0M NaOH into a foam cup and then dumped 25.4mL of 2.0M NH4Cl solution. My lowest temperature was 22.5 degrees C (before mixing), and highest was 23.8 degrees C (after mixing).

The third reaction I measured 25.3mL of 2.0M HCl into a foam cup and then dumped 25.5 mL of 2.0M NH3 solution. My lowest temperature was 22.4 degrees C (before mixing), and highest was 31. 7 degrees C (after mixing thr two solutions.

Can somebody help me and show me what to do possibly, I really have no clue. Thank you so much!

 

[GCT]

You need to figure out the heat of the reaction by the change in temperature of the water. What is the equation that needs to be used for this?

Find the equation that relates enthalpy to energy.

Then it is a matter of dividing by the appropriate units of the reactant to get your answer. If you have trouble , simply consult NIST or CRC.

 

[Blueshift5]

I can provide some guidance on how to approach calculating the enthalpy change for these reactions. First, it is important to understand that enthalpy is a measure of the heat energy released or absorbed during a reaction. It is reported with respect to a reactant, meaning the enthalpy change for a reaction will be different depending on which reactant is used as the reference point.

In this case, the problem asks for the enthalpy change in terms of kJ/mol for one of the reactants, either HCl or NaOH. To calculate the enthalpy change, you will need to use the heat capacity equation: q = m x C x deltaT, where q is the heat energy released or absorbed, m is the mass of the substance, C is the specific heat capacity, and deltaT is the change in temperature.

For the first reaction, you will need to calculate the heat energy released or absorbed by the reaction using the temperature change and the heat capacity of the solution (which can be found in a reference table). This will give you the enthalpy change in terms of kJ. Then, you can divide by the moles of the chosen reactant (either HCl or NaOH) to get the enthalpy change per mole.

Repeat this process for the other two reactions, and you will have the enthalpy change in terms of kJ/mol for each reaction. Remember to use the same reactant as the reference point for all three reactions.

I hope this helps guide you in calculating the enthalpy change for these reactions. If you have any further questions, please don't hesitate to ask for clarification. Good luck!