Ice must absorb heat to melt into water. What must water do to evaporate?
2 answers:
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Answer :
Charles's Law : It is defined as the volume is directly proportional to the temperature of the gas at constant pressure and number of moles.
Mathematically,
Boiling water bath Cool bath 1 Cool bath 2
Temperature (⁰C) 99 17 2
Temperature (K)(T) 273+99=372 273+17=290 273+2=275
Volume of water 0.0 27.0 34.0
in cool flask (mL)
Volume of water= 135.8 135.8 135.8
Air in flask (mL)
Volume of air 135.8 108.8 101.8
in cool flask (V)
The graph volume versus temperature for a gas is shown below.
As long as the equation in question can be expressed as the sum of the three equations with known enthalpy change, its can be determined with the Hess's Law. The key is to find the appropriate coefficient for each of the given equations.
Let the three equations with given be denoted as (1), (2), (3), and the last equation (4). Let
,
, and
be letters such that
. This relationship shall hold for all chemicals involved.
There are three unknowns; it would thus take at least three equations to find their values. Species present on both sides of the equation would cancel out. Thus, let coefficients on the reactant side be positive and those on the product side be negative, such that duplicates would cancel out arithmetically. For instance, shall resemble the number of
left on the product side when the second equation is directly added to the third. Similarly
:
:
:
Thus
and
Verify this conclusion against a fourth species involved- for instance. Nitrogen isn't present in the net equation. The sum of its coefficient shall, therefore, be zero.
Apply the Hess's Law based on the coefficients to find the enthalpy change of the last equation.