At Equilibrium The Concentration of Hi 0.069 M Calculate Kc
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Reviewed by Calculator Editorial Team
When a chemical reaction reaches equilibrium, the equilibrium constant (Kc) describes the ratio of product concentrations to reactant concentrations. This calculator helps determine Kc when the concentration of hydrogen iodide (HI) is 0.069 M, assuming a simple dissociation reaction.
Introduction
The equilibrium constant Kc is a fundamental concept in chemical equilibrium. For a general reaction:
aA + bB ⇌ cC + dD
The equilibrium constant is expressed as:
Kc = [C]c[D]d / [A]a[B]b
Where [X] represents the molar concentration of species X at equilibrium.
Formula for Kc
For the dissociation of hydrogen iodide:
2HI(g) ⇌ H2(g) + I2(g)
The equilibrium constant expression becomes:
Kc = [H2][I2] / [HI]2
This formula relates the concentrations of hydrogen gas, iodine gas, and hydrogen iodide at equilibrium.
Calculation Example
Suppose we have a system where the concentration of HI is 0.069 M at equilibrium. If we know the concentrations of H2 and I2, we can calculate Kc.
For example, if [H2] = 0.0345 M and [I2] = 0.0345 M:
Kc = (0.0345 × 0.0345) / (0.069)2 = 0.0012
This means the equilibrium favors the reactants (HI) over the products (H2 and I2) by a factor of 0.0012.
Interpreting Results
The value of Kc tells us about the position of equilibrium:
- If Kc > 1, the reaction favors products at equilibrium
- If Kc = 1, the reaction is at equilibrium with equal concentrations
- If Kc < 1, the reaction favors reactants at equilibrium
In our example with Kc = 0.0012, the reaction strongly favors the reactants (HI).
FAQ
What units are used for concentrations in Kc?
Concentrations in Kc are typically expressed in molar (M) units, which is moles per liter (mol/L).
Can Kc be calculated without knowing all concentrations?
No, Kc requires knowing the concentrations of all species involved in the reaction at equilibrium.
How does temperature affect Kc?
Kc is temperature-dependent. The relationship is described by the van't Hoff equation, which connects Kc to temperature changes.