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### Topic: Enthalpy changes.  (Read 3145 times)

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#### zakid

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##### Enthalpy changes.
« on: February 17, 2009, 02:59:47 PM »
I want to find out if my reasoning is correct...

I want to calculate the enthalpy change of this reaction
NaHCO3 + HCl -> NaCl + CO2 + H2O

...using Hess's Law...

1)  2NaHCO3 -> Na2CO3 + CO2 + H2O

2)  Na2CO3 + 2HCl -> 2NaCl + CO2 + H2O

1) 7g of hydrogencarbonate
50cm^3 of hydrochloric acid
deltaT=5K

2) 4g of hydrogencarbonate
50cm^3 of hydrochloric acid
deltaT=9,5K

2H1=H2+H3

H2= 0,057 x 4,18 x 5 = -1,19kJ

H3=0,054 x 4,18 x 9,5 = 2,14kJ

H1=(-1,19kJ - 2,14kJ):2= -1,665kJ

Is this correct?
« Last Edit: February 17, 2009, 03:30:10 PM by zakid »

#### Astrokel

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##### Re: Enthalpy changes.
« Reply #1 on: February 17, 2009, 08:50:50 PM »
Quote
2H1=H2+H3
Which is which?
No matters what results are waiting for us, it's nothing but the DESTINY!!!!!!!!!!!!

#### Donaldson Tan

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##### Re: Enthalpy changes.
« Reply #2 on: February 18, 2009, 07:03:37 AM »
You might need to some labelling of your terms. Also use the sub and sup tags. It would help a lot in interpreting your text.
"Say you're in a [chemical] plant and there's a snake on the floor. What are you going to do? Call a consultant? Get a meeting together to talk about which color is the snake? Employees should do one thing: walk over there and you step on the friggin� snake." - Jean-Pierre Garnier, CEO of Glaxosmithkline, June 2006

#### zakid

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##### Re: Enthalpy changes.
« Reply #3 on: February 18, 2009, 01:31:21 PM »
Nevermind, I've already figured it out. I'll try using better notation next time.