[shilohmedia]

I have a three part question:

Aqueous sodium hydrogen carbonate solution reacts with hydrogen chloride. The reaction produces salt, water and carbon dioxide gas. The reaction absorbs 12.7KJ of heat. Answer the following questions:

A. Write the balanced thermochemical equation representing this reaction.

B. How much energy will be absorbed if 1/2 moles of carbon dioxide gas were produced in this reaction. Write the balanced thermochemical equation for this reaction.

C. How much energy will be absorbed if 3.01 x 1023 molecules of aqueous HCl were present in the system. Write the balanced thermochemical equation for this reaction.

[Arkcon]

Well, lets try to start this.  Begin by drawing a balanced chemical reaction.  That's not only what part a asks for, you'll also need it to figure out the rest.  You've been given products and reactants, and you've been told the reaction absorbs heat, so where would that go?

[shilohmedia]

Here's what I have to start with:

NaHCO₃ + HCl  NaCl + H₂O + CO₂ 12.7KJ

[UG]

NaHCO₃ + HCl  NaCl + H₂O + CO₂ 12.7KJ

This reaction you have written is good, but you need to add your change in enthalpy sign in front of the number (for example, ΔH_reaction = 12.7 kJ/mol ). You are told that the reaction absorbs 12.7 kJ of heat, this means that for every mole of the reaction you have written above the energy absorbed is 12.7 kJ. Part B asks how much heat is absorbed if 0.5 moles of CO₂ gas is produced, ie, the entire reaction is halved, this part should be simple enough? For part C you need to find firstly how many moles of HCl is 3.01 x 10²³ molecules of HCl, do you know how to do this with Avagadro's number?

[shilohmedia]

I think I do. The problem I am finding is the changes to the equation gives me the same answer and it doesn't seem right that both answers would be the same. 1/2 CO₂ and 3.01 x 10²³ means I half the entire equation in both instances, correct?

[UG]

1/2 CO₂ and 3.01 x 10²³ means I half the entire equation in both instances, correct?

Yes I agree, the answer will be the same on both instances.

[shilohmedia]

Here's what I came up with for both:

1/2NaHCO₃ + 1/2HCl  1/2NaCl + 1/2H₂O + 1/2CO₂ ΔH=6.35KJ

Correct?

[shilohmedia]

Do any of you guys know what my professor is talking about when he asks me to define "isolated reaction"?

[UG]

1/2NaHCO₃ + 1/2HCl   1/2NaCl + 1/2H₂O + 1/2CO₂ ΔH=6.35KJ

Correct?

Yes, very much so.

Do any of you guys know what my professor is talking about when he asks me to define "isolated reaction"?

Apart from maybe "a reaction which occurs in an isolated system" I have no idea what he means. 

http://en.wikipedia.org/wiki/Isolated_system

[shilohmedia]

Could he be talking about an isolation reaction? Not that I know what that is, but it sounds more familiar ...

[UG]

I can't really say without knowing what context these terms were used in.

[shilohmedia]

Unfortunately it is from a list of definitions he expects us to know. The list is as follows:

Photon
Principle Quantum Number
Enthalpy
Heat of reaction
Isolated reaction

I have all the others, but this one cannot be found anywhere.
 

[UG]

Ah ok, if you're talking about enthalpy and heat of reaction then isolated reaction could very well mean what I said before "a reaction which occurs in an isolated system, there is no exchange of energy and mass". I am 90% sure this is what he wants

[shilohmedia]

Dude, thank you so much. This has been eating at me because I cannot find it in the book in those terms anywhere or on the internet. I have been haunted by thinking he surely has a typo here. The problem is my test is this weekend (a weekend only class). That makes sense when you describe it.