Q=MCdelta T w/phase change, cant get a logical answer
Join Date: Mar 2006
Posts: 5,162
**Found my Error, Ignore**
I need to figure this out before i get tested on something similar
cup of 200 ml water at 95C. Put 40g dry ice(molar mass=44g/mol) initially at negative 78C, with enthalpy of sublimation of 8.76kJ/mol. Assume final temp of CO2 gas and water are equal. what is final temp?
specific heat of water 4.186j/gC
"" of C02 gas .85 j/gC
How i went about doing it,
40gCO2/46mol * 8.76kj/mol= 7617 j to sublime dry ice.
I took 7617j and Q=mcdeltaT to find the water drops 9.01C to sublime ice, then i took the new water temp and used it in the MCdeltaT=MCdeltaT style.
(200)(4.186)(T-85.99)=(40)(.850)(T- -78)
And i end up with a number that says the water is getting warmer, BLEEEEH.
Please help i need to figure how to do a problem like this before a test.