The following reaction is at equilibrium at a pressure of 1 atm, in a closed container.
NaOH(s) + CO2(g) NaHCO3(s); ΔH°rxn < 0
Which, if any, of the following actions will decrease the concentration of CO2 gas present at equilibrium?
A. lowering the temperature
B. adding more solid NaOH… solids don’t affect Keq.
C. increasing the volume of the container... technically, this makes sense, but think thermodynamics regarding the problem
D. adding N2 gas to double the pressure… not in reaction
why is the answer A
Because when you lower the temperature, it's like giving a cold shoulder to CO2. It becomes less motivated to stay in the equilibrium party and decides to leave, decreasing its concentration. It's the equivalent of CO2 saying, "No chilly vibes for me, I'm outta here!"
The answer is A - lowering the temperature.
When the temperature is lowered in an exothermic reaction (ΔH°rxn < 0), the equilibrium will shift in the direction that produces heat. In this case, CO2 gas is on the product side of the reaction, and by decreasing the temperature, the equilibrium will shift toward the side that produces heat, favoring the formation of more NaHCO3 solid instead of CO2 gas. As a result, the concentration of CO2 gas present at equilibrium will decrease.
The answer is A. lowering the temperature.
To understand why lowering the temperature decreases the concentration of CO2 gas at equilibrium, we need to consider Le Chatelier's principle.
Le Chatelier's principle states that when a system at equilibrium is subjected to a stress, it will shift in a way that minimizes the effect of the stress.
In this reaction, the forward reaction is the formation of NaHCO3 from NaOH and CO2, and the reverse reaction is the decomposition of NaHCO3 to NaOH and CO2. Lowering the temperature is considered a stress because it reduces the kinetic energy of the particles in the system.
According to Le Chatelier's principle, when the temperature is lowered, the system will shift in the direction that produces more heat. Since the forward reaction is exothermic (ΔH°rxn < 0), it will be favored in the direction that produces heat. Therefore, the equilibrium will shift to the right, resulting in a decrease in the concentration of CO2 gas.
To summarize, lowering the temperature of the system will cause the equilibrium position to shift to the right, resulting in a decrease in the concentration of CO2 gas at equilibrium.
Write the reaction this way.
NaOH(s) + CO2(g) ==>NaHCO3(s) + heat (and I REALLY don't like it that you can't put in an arrow.)
A. So adding heat MUST drive the reaction to the left; therefore, lowering the T will do the opposite.
B. right.
C. No it doesn't make sense. Decreasing volume is increasing pressure which shifts reaction to the right(fewer moles) so decreasing pressure will shift to the left and the problem wants to decrease CO2.
D. See C.