Calculate the amount of heat needed to melt 79.2 g of solid octane and bring it to a temperature of -52.5 C. Be sure your answer has a unit symbol and the correct number of significant digits.

Answer 1

We need more information to answer this question.

We need to know ...

freezing/melting point of octane

specific heats for the different phases of octane

∆Hfusion of octane

etc.

EIDT: THIS IS A TERRIBLE QUESTION IF NONE OF THE THERMOCHEMICAL DATA ARE PROVIDED

I was able to find the freezing point of octane to be -57ºC BUT unable to find the other information needed. Here is how to do the problem if YOU can find the missing data.

Assuming the solid octane is at -57ºC (and not lower than that, which isn't stated in the problem), you will have to find the ∆Hfusion for octane and use it in units of J/g or kJ/g.

q = ∆Hfusion x 79.2 g = heat needed to melt the solid octane (phase transition)

Then find the specific heat of liquid octane (C) and be sure it is in units of J/gº

q = (79.2 g)(specific heat in J/gº)(4.5º) = heat needed to get the liquid from -57º to -52.5º

Add the 2 results together to get your answer. It will be in units of Joules.