Arrange the following elements (E, K, P, B) according to increasing atomic radius
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Answer : The standard enthalpy of formation of ethylene is, 51.8 kJ/mole
Explanation :
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 formation reaction of will be,
The intermediate balanced chemical reaction will be,
(1)
(2)
(3)
Now we will reverse the reaction 1, multiply reaction 2 and 3 by 2 then adding all the equations, we get :
(1)
(2)
(3)
The expression for enthalpy of formation of will be,
Therefore, the standard enthalpy of formation of ethylene is, 51.8 kJ/mole
Explanation:
(a). The given data is as follows.
Volume of one glass of water = ml = 220 ml
Volume of 4 glass of water = = 880 ml
We known that density of water is 1 g/ml. Therefore, calculate the mass of water as follows.
Mass of water =
= 880 gm
= 0.88 Kg (as 1 kg = 1000 g)
The relation between heat energy, mass and temperature change is as follows.
Q =
Putting the given values into the above formula as follows.
Q =
=
= 124.5 kJ
Hence, the body have to supply 124.5 kJ to raise the temperature of the water to 37 degree C.
(b). As we know that the heat of fusion of ice is 333 J/g.
So, energy required for g or 840 g is as follows.
= 279.72 kJ
Heat capacity of water= 4.184
Now, heat energy will be as follows.
Q =
= 130.03 kJ
Therefore, total heat required = (279.72 + 130.03) kJ
= 409.75 kJ
Hence, for the given situation your body should lose 409.75 kJ of heat.