Unit 7: Topic 1 - Introduction to Equilibrium Flashcards
Define what a reversible process is, and give some examples. How is this different from a reversible reaction?
A reversible process is any physical or chemical process where both the forward reaction (reactants to products) and the reverse reaction (products to reactants) both proceed in most situations. For example, evaporation of water is a reversible process because the reverse, condensation of steam, proceeds relatively quickly in most situations.
A reversible reaction is a reaction in which conversion of reactants to products occurs simultaneously with the conversion of products to reactants. For example, when a weak acid such as HF dissociates, the reaction is HF + H2O ⇌ F(-) + H3O(+), with the double arrow implying that HF dissociates to H3O+ and simultaneously H3O reacts to form HF.
What is equilibrium in terms of a chemical reaction?
A chemical reaction in equilibrium shows no observable signs of change. Reactants and products are both present in concentration (and/or pressure), and this amount stays constant when the system reaches equilibrium.
Explain what happens when a chemical reaction reaches equilibrium.
Even though chemical equilibrium shows no observable signs of change and concentrations of reactants and products stay constant, equilibrium is dynamic. Both forward and reverse reactions proceed at equal rates so that the net concentrations do not change.
Interpret this graph of rates with the reaction N2O4 ⇌ 2NO2 and determine when the reaction reaches equilibrium.
From the graph, the rate of reaction of NO2 (the reverse reaction) increases from 0 and eventually plateaus around 0.25 * 10^6 M/s. Similarly, the rate of reaction of N2O4 (the forward reaction) decreases from the initial rate down to 0.25 * 10^6 M/s. Eventually, the forward and reverse reaction rates will become equal and stay constant. Equilibrium will occur around 2000ns, as based on the graph.
