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##K_w## and auto-ionization of water
The ##K_w## value decreases as the temperature decreases. Is the auto-ionization of water an exothermic or endothermic reaction in the forward direction?
Water is able to auto-ionize into ##H_3O^{+1}## and ##OH^{-1}## in an equilibrium reaction:
##H_2O_{(L)} + H_2O_{(L)} \leftrightharpoons H_3O^{+1}_{(aq)} + OH^{-1}_{(aq)}##
The equilibrium constant for this reaction is defined as ##K_w = [H_3O^{+1}][OH^{-1}]##. It is known that the ##K_w## value increases as the temperature increases and decreases as the temperature decreases.
If ##K_w## is decreasing because temperature is decreasing, it means that the concentration of products is decreasing and so the reaction must move forward to produce more products and restore equilibrium. This means that heat must be a by-product of the reaction and therefore the overall reaction must be exothermic so that the equilibrium will shift right as the temperature decreases.
Is this reasonable?
Homework Statement
The ##K_w## value decreases as the temperature decreases. Is the auto-ionization of water an exothermic or endothermic reaction in the forward direction?
Homework Equations
The Attempt at a Solution
Water is able to auto-ionize into ##H_3O^{+1}## and ##OH^{-1}## in an equilibrium reaction:
##H_2O_{(L)} + H_2O_{(L)} \leftrightharpoons H_3O^{+1}_{(aq)} + OH^{-1}_{(aq)}##
The equilibrium constant for this reaction is defined as ##K_w = [H_3O^{+1}][OH^{-1}]##. It is known that the ##K_w## value increases as the temperature increases and decreases as the temperature decreases.
If ##K_w## is decreasing because temperature is decreasing, it means that the concentration of products is decreasing and so the reaction must move forward to produce more products and restore equilibrium. This means that heat must be a by-product of the reaction and therefore the overall reaction must be exothermic so that the equilibrium will shift right as the temperature decreases.
Is this reasonable?
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