Calculating Total Energy with Dimensional Analysis | Screenshot Included

[JessicaHelena]

Homework Statement

Please look at the screenshot.

Homework Equations

dimensional analysis

The Attempt at a Solution

Since the heat capacity is given as 11.3 kJ/(C*g), and energy is measured in Joules (or kJ), I thought to multiply 11.3 by the change in temp (7.3 C) and also 1.50 g of methane.

However, as you can see, what my teacher did is quite different (does not have the grams).

but he explicitly states that total energy = energy required per deg x no. of deg... where'd the grams go then?
Please help me out!

 

[boredfello]

Homework Statement

Please look at the screenshot.

Homework Equations

dimensional analysis

The Attempt at a Solution

Since the heat capacity is given as 11.3 kJ/(C*g), and energy is measured in Joules (or kJ), I thought to multiply 11.3 by the change in temp (7.3 C) and also 1.50 g of methane.

However, as you can see, what my teacher did is quite different (does not have the grams).
but he explicitly states that total energy = energy required per deg x no. of deg... where'd the grams go then?
Please help me out!

You’re given the SH of the bomb calorimeter. Then it seems to switch to what’s called a calorimeter constant, which is just J/C. The question seems oddly worded and is perhaps just a mistake in the notes?

You might want to email your professor and ask for clarification or wait for another reply here from someone to see something I missed or am misunderstanding myself.

 

[Borek]

My bet is that is a mistake, 11.3 looks like it is intended to be a heat capacity, not a specific heat capacity (note you are not given calorimeter mass which makes the question impossible to solve).

 

[epenguin]

I agree with the last two posters that to call it specific heat capacity is unfortunate, it is just a heat capacity (and should not contain g).
But as far as it goes the calculation appears to me correct.
Where have the grams gone? You just need to convert the kJ for that amount of octane in that particular experiment to something of more general value, the kJ per mole octane, or maybe for engineers kJ/Kg.