Answer : The change in enthalpy of the reaction is, -310 kJ
According to Hess’s law of constant heat summation, the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps.
According to this law, the chemical equation can be treated as ordinary algebraic expression and can be added or subtracted to yield the required equation. That means the enthalpy change of the overall reaction is the sum of the enthalpy changes of the intermediate reactions.
The given main reaction is,
The intermediate balanced chemical reaction will be,
(1) 
(2) 
(3) 
Now we will reverse the reaction 1 and multiply reaction 1 by 2, reaction 2 by 2 and reaction 3 by 3 then adding all the equations, we get :
(1) 
(2) 
(3) 
The expression for enthalpy of formation of 
will be,
Therefore, the change in enthalpy of the reaction is, -310 kJ
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There are many different forms of energy such as electrical, thermal, nuclear, mechanical, electromagnetic, sound, and chemical.
Answer:
3. Her angular speed increases because her angular momentum is the same but her moment of inertia decreases
Explanation:
II ωi the intial angular momentum of the skater. Her angular momentum changes to If ωf after pulling her arms in.
It must be noted that If is less than II, then it is because her arms now go round not far from the rotation axis which brings down the mementos of inertia.
Angular momentum does not change since torque is O.
Note: the mathematical representations are better written on the attached diagram.
You'd use the equation kinetic energy=mass*0.5*speed^2
So you'd rearrange this to get mass =kinetic energy /0.5 *speed^2
Which is mass= 1500J/0.5*35^2
=2.44897959183673469........kg
