Answer : The energy removed must be, 29.4 kJ
Explanation :
The process involved in this problem are :
The expression used will be:
where,
= heat released for the reaction = ?
m = mass of benzene = 94.4 g
= specific heat of solid benzene =
= specific heat of liquid benzene =
= enthalpy change for fusion =
Now put all the given values in the above expression, we get:
Negative sign indicates that the heat is removed from the system.
Therefore, the energy removed must be, 29.4 kJ
The balanced chemical reaction is written as:
2K + F2 = 2KF
We are given the amount of potassium to be used in the reaction. THis will be the starting point. We do as follows:
23.5 g K ( 1 mol / 39.10 g) (1 mol F2 / 2 mol K ) ( 22.4 L / 1 mol ) = 6.73 L F2 gas needed
A strong electrolyte like MgCl2 dissociates completely as per the following reaction:
As you can see, from 1 molecule of MgCl2 produces 3 ions on dissociation.
So, 1 mole of MgCl2 produces 3 moles of ions.
Now, Moles of MgCl2 = Volume x Molarity
= 0.04 x 0.345 [Change volume to Litres]
= 0.0138 moles
Now, total moles of ions = 0.0138 x 3 = 0.0414
The amount of heat needed would be the specific heat multiplied by the mass of the substance and the temperature difference. In this case, the mass would be 75.0–g, the specific heat would be 0.449 j/g °c, and the temperature difference would be <span>1535 -25= 1510
Then the calculation would be: </span>0.449 j/g °c * 75g * 1510°c = 50,849.25J
In calorie it would be: 50849.25J / 4.184J/cal= 12,153.26 calorie