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# Physical Chemistry Help Watch

1. Onegram of magnesium is reacted with excess fluorine gas in acalorimeter with a heat capacity of 2 kJ K-1causing the temperature to rise from 25°C to 39°C.

a)Write a balanced chemical equation for this reaction.
b)Calculate the enthalpy of formation (ΔfHθ)at 298K

Also can you explain how you got the answers too, methods please
2. (Original post by chemistry2014)
Onegram of magnesium is reacted with excess fluorine gas in acalorimeter with a heat capacity of 2 kJ K-1causing the temperature to rise from 25°C to 39°C.

a)Write a balanced chemical equation for this reaction.
b)Calculate the enthalpy of formation (ΔfHθ)at 298K

Also can you explain how you got the answers too, methods please
The enthalpy of formation is energy per mole of product.

The heat capacity of the calorimeter means that 2kJ of energy are needed to increase the temperature by 1 degree Celsius (or Kelvin).
3. (Original post by chemistry2014)
Onegram of magnesium is reacted with excess fluorine gas in acalorimeter with a heat capacity of 2 kJ K-1causing the temperature to rise from 25°C to 39°C.

a)Write a balanced chemical equation for this reaction.
b)Calculate the enthalpy of formation (ΔfHθ)at 298K

Also can you explain how you got the answers too, methods please
Calculating the enthalpy of formation depends on how you've been taught it. Have you done thermochemical cycles?

EDIT: Actually, q=m x c x deltaT may be more appropriate for the information you're given.
4. (Original post by Nistar)
Calculating the enthalpy of formation depends on how you've been taught it. Have you done thermochemical cycles?

EDIT: Actually, q=m x c x deltaT may be more appropriate for the information you're given.
This is not needed as you are given the heat capacity of the calorimeter ...
5. (Original post by charco)
This is not needed as you are given the heat capacity of the calorimeter ...
Haha, in all honesty I've confused myself.
Why do I keep thinking you can calculate the energy change with q = m x c x deltaT then divide by moles of product to get the enthalpy of formation?
6. (Original post by Nistar)
Haha, in all honesty I've confused myself.
Why do I keep thinking you can calculate the energy change with q = m x c x deltaT then divide by moles of product to get the enthalpy of formation?
You just need to calculate q = heat capacity x temperature change, there is no need for any mass ...

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