The decomposition of ammonium hydrogen sulfide that is shown below is an endothermic process.
NH4HS(s) reverse reaction arrow NH3(g) + H2S(g)
A 6.1589 g sample of the solid is placed in an evacuated 4.000 L vessel at exactly 24°C. After equilibrium has been established, the total pressure inside is 0.709 atm. Some solid NH4HS remains in the vessel.
a.)If the volume of the vessel were doubled at constant temperature, what would happen to the amount of solid in the vessel?
So K = p(NH3)*p(H2S)
If the volume is doubled, the pressure is halved; therefore, the reaction will shift to the right and more of the NH4HS will decompose. Thus, the solid will be decreased.
Based on Le Chatelier's principle, when the volume of the vessel is doubled at constant temperature, the system will try to counteract the change by shifting towards the side with fewer moles of gas. In this case, the gaseous products (NH3 and H2S) have a total of 2 moles of gas, while the solid NH4HS has 0 moles of gas.
Therefore, to decrease the overall moles of gas, the reverse reaction (formation of NH4HS) will be favored. As a result, more solid NH4HS will form in the vessel.
To determine what would happen to the amount of solid in the vessel if the volume were doubled at constant temperature, we need to consider Le Chatelier's principle.
Le Chatelier's principle states that when a system at equilibrium is subjected to a change, it will tend to counteract that change and establish a new equilibrium position.
In this case, if we double the volume of the vessel while keeping the temperature constant, it can be considered as a decrease in pressure. According to Le Chatelier's principle, the system will try to counteract this change by shifting the equilibrium in a direction that increases the pressure.
The decomposition of NH4HS into NH3 and H2S is an endothermic process, meaning it absorbs heat from the surroundings. When the pressure decreases, the reaction will shift in the direction that produces more gas molecules to increase the total pressure.
In the given reaction, NH4HS(s) reverse reaction arrow NH3(g) + H2S(g), the number of gas molecules increases from one (NH4HS) to two (NH3 and H2S). Therefore, the reaction will shift towards the products (NH3 and H2S) to increase the total gas pressure.
As a result, if the volume of the vessel is doubled under constant temperature conditions, more of the solid NH4HS will decompose to produce NH3(g) and H2S(g). Thus, the amount of solid NH4HS remaining in the vessel will decrease.