[Frederick95]

Calculate the molar enthalpy of combustion of acetone, using the experimental evidence.

           Given:
           Mass (m) of water: 100.0 g
           Specific heat capacity(c) of aluminum: 0.91 J/ g degrees Celsius
           Mass (m) of aluminum can: 50.0 g
           Initial temperature (Ti) of calorimeter: 20.0 degrees Celsius
           Final temperature(Tf) of calorimeter: 25.0 degrees Celsius
           Mass (m) of acetone burned: 0.092 g

MY WORK IS AS FOLLOWS
           
           Required:
     Molar enthalpy of combustion of acetone?

     Analysis
           ΔT = tf - ti
           = 25.0 oC - 20.0 oC
           = 5.0 oC

           Q = mc DT
              = (100.0 g) (0.91 J/(goC)) (5.0 oC)
              = 455 J
           H = - Q = - 455 J = -0.455 kJ
     Number of moles (n) = (given mass (g))/(gram-formula mass)
                                    =


HOW DO I ACCOMPLISH THIS STEP?
THANKS AGAIN

[Borek]

Stop starting new threads with the same information, if you have additional questions - reuse your old thread. This is final warning.

[mo_1984]

i have the same rpoblem as fredrick listed. it is the EXACT same question he asked any1 plz help me how to do it.

[ARGOS++]

Dear Frederick95, Dear Mo_1984;

First Part:  ΔT is OK!

But Part 2:  Q = ….. is wrong!    It must be:  Q = Q_Water + Q_Al !!
(Remember: m_Water is not equal m_Al.)

Frederick95:  I think you know, since a short while, how to finish.

I hope it helps for both of you.


Good Luck!
                    ARGOS⁺⁺

[mo_1984]

yea but if u r putting in the mass of alu then u have to add the heat capacity also???

[ARGOS++]

Dear Mo_1984;

You’re right!, –   c_Al for Al, and c_Water  for …. !

Good Luck!
                    ARGOS⁺⁺

[mo_1984]

so when using q= mct formula for m add alu and water masses and for c add heat capacity for both???
and r u sure abt this man because every time i ask some1 they are telling me different answers so i am soo confused.

[Frederick95]

Can you show us an example of this Argos?

Please

Thank you for any further help

[ARGOS++]

Dear Mo_1984;

NO!,  –   I told you:  Q_Total  = Q_Water + Q_Al !!
You need twice: Q = mcΔT !!!

Good Luck!
                    ARGOS⁺⁺

[ARGOS++]

Dear Frederick95, Dear Mo_1984;

Q_Total  = Q_Water + Q_Al   =  m_Wc_WΔT + m_Alc_AlΔT.

I hope I have been of help to you.

Good Luck!
                    ARGOS⁺⁺

[Frederick95]

Thank you Argos:)

[Frederick95]

Argos, do you have a link to any website that explains this formula?

[ARGOS++]

Dear Frederick95;

Not at the moment, -  but think about: 

At begin both (Water and Calorimeter, build from Al) have the Temperature T_i.
After burning the Acetone both must have the identical Temperature T_f.
Conclusion:
    Both must have taken enough Heat corresponding to their individual Mass m and individual  c!

That’s all.             You have to make you “A Picture” (see below).


Good Luck!
                    ARGOS⁺⁺

[ARGOS++]

Dear Frederick95, Dear Mo_1984;

Two (of a Lot) Links that may help a bit:

"Calorimetry”      "Calorimeter”

Good Luck!
                    ARGOS⁺⁺

[Frederick95]

Argos -----Thanks

But.. My sum is 2317.5 kJ

I must find the molar enthalpy.

Is there a formula for this? I cannot find it:(