Kc Flashcards
What is Kc?
the equilibrium constant
How can we calculate the number of moles in a equilibrium mixture?
titration if we know the equatiom we can work out the number of moles from the other components
How can we find the concentration?
moles / volume
What is the expression for Kc?
aA + bB <=> xX + yY
eqm Mwans concentration at equilibrium
[X]eqmx + [Y]eqmy
[A]eqma + [B]eqmb
What are the cocndition for Kc to be accurate?
the expression is constant if the temperature is constant
What is the general rule for the temperature change and the effect on the equilibrium constant?
exothermic - increasing the temperature decreases the equilibrium constant
endothermic - increasing the temperature increases the equilibrium constant
What is the effect on Kc if concentrations changed?
Kc remains constant as long as temperature isconstant
adding something to the bottom of the equilibrium law expressions makes it larger
to restore the situation, what was added to the bottom line reacts, restoring the concentration on the bottom line, thus increases the value in the top lime
the combined effect is to restore the fraction to the original value of Kc
What can the value of Kc tell us about the position of the equilibrium?
equilibrium expression is always in the form products / reactants
so:
if Kc is is greater than 1, the equilbrium position is to the right, vice versa
When do units cancel?
when there are an equal number of moles on either sides of the equation
Why does V not need to be known in equation N2 + O2 → 2NO
- V cancels in expression
- moles of reactants = moles of products
- The value of Kc for this reaction is 1 × 10–5 at 1500 K.
- Explain the significance of this value for an industrial chemist interested in manufacturing nitrogen monoxide by the direct combination of the elements.
- The product yield is very small
- Yield does not justify cost of producing high temp
