The volume and temperature was recorded during the very first appearance of salt crystals in the solution. Ten grams of KNO 3 was obtained and transferred to a test tube with 7.5 mL water. Hence, the purpose of this activity is to determine the thermodynamics variables of ∆H, ∆S, and ∆G for the dissolution reaction of potassium nitrate in water by investigating the dependence of the solubility equilibrium constant across a range of temperature. LnK = -∆H/RT + T∆S/RT = -∆H/R * (1/T) + ∆S/Rīy plotting In Ksp versus 1/T, the slope of the line is –ΔH/R and the y-intercept is ΔS/R. Which can then be rearranged equation into the form of a straight line as Equating the third and fourth equations results in
#Entropy and enthalpy free#
The equation can be simply written asĪ mathematical relationship also exists between the free energy change and the solubility equilibrium constant. The mathematical relationship between the changes in free energy, enthalpy, and entropy is illustrated by Gibbs-Helmholtz equation which can be derived by combining the First and Second Laws of Thermodynamics. The free energy change (ΔG) for a salt dissolving in water indicates whether the process will occur spontaneously. The energy difference between the solid salt and its dissolved ions is known as the enthalpy change (ΔH), and the relative disorder of the dissolved ions is an indication of the entropy change (ΔS). Interestingly, the solubility of a salt can be used to determine the thermodynamic properties of the reaction. As solubility increases with increasing temperature, the value for Ksp for a compound also increases with temperature. The equilibrium constant is a measure of solubility expressed as a product of the molar concentration of ions.
The equilibrium constant expression defines the equilibrium constant (Ksp) for KNO 3 dissolving in water which can expressed as K sp =
This is known as a saturated solution in which the rate of dissociation is equal to the rate of precipitation. The two-sided arrow indicates that the reaction is reversible and undissolved solid is in equilibrium with the dissolved ions. Aqueous potassium nitrate (KNO 3) dissociates When a soluble salt is dissolved in water, it will dissociate into ions.
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