Le Chatelier's Principle: Flashcards

10 cards

Question
State Le Chatelier's principle.
Answer
If an equilibrium is disturbed, its position shifts in the direction that partly counteracts the change.
Question
A reactant is added to an equilibrium mixture. Which way does it shift?
Answer
To the right (toward products): Q becomes smaller than K.
Question
A product is removed. Which way does the equilibrium shift?
Answer
To the right, to replace some of the product.
Question
How does increasing the pressure (smaller volume) affect a gas equilibrium?
Answer
It shifts toward the side with fewer moles of gas.
Question
Which way does $\ce{N2 + 3H2 <=> 2NH3}$ shift at higher pressure?
Answer
Right: 4 mol of gas become 2 mol.
Question
How does raising the temperature affect an exothermic equilibrium?
Answer
It shifts left (the endothermic direction) and K decreases.
Question
Which change alters the value of K?
Answer
Only a change in temperature.
Question
What does a catalyst do to an equilibrium?
Answer
Nothing to its position or K; equilibrium is just reached faster.
Question
$\ce{N2O4 <=> 2NO2}$ (ΔH = +57 kJ; NO₂ is brown). What happens to the colour on heating?
Answer
It gets darker: the endothermic forward reaction is favoured, forming more NO₂.
Question
Does pressure affect $\ce{H2 + I2 <=> 2HI}$ ?
Answer
No: there are 2 mol of gas on each side.