Question

Consider the statement: The equilibrium constant of a reacting mixture of solid \(\mathrm{NH}_{4} \mathrm{Cl}\) and gaseous \(\mathrm{NH}_{3}\) and \(\mathrm{HCl}\) is \(0.316 .\) List three important pieces of information that are missing from this statement.

Short answer

The missing information from the statement includes: the temperature at which the reaction is happening, the balanced chemical equation representing the reaction, and whether the equilibrium constant is in terms of pressure or concentration.

Step-by-step solution

Missing Information 1

One piece of missing crucial information is temperature. Temperature affects the magnitude of the equilibrium constant. Therefore, we need to know the temperature at which the reaction equilibrium constant is 0.316. This would enable to understand and compare this equilibrium constant with others.

Missing Information 2

The consideration of the involved chemical entities is missing. Although solids such as \(\mathrm{NH}_{4} \mathrm{Cl}\) and gases like \(\mathrm{NH}_{3}\) and \(\mathrm{HCl}\) have been mentioned, the actual chemical reaction has not been provided. The stoichiometry of the reaction affects the equilibrium constant. Knowing the reaction will allow us to understand how the substances interact in order to reach the equilibrium state. A balanced chemical equation would provide clarity.

Missing Information 3

The third missing piece of information is about the pressure or concentration of gases. For gaseous reactions, the equilibrium constant can be expressed in terms of either partial pressures or molar concentrations. It is crucial to specify whether the equilibrium constant given is in terms of concentration (\(K_c\)) or pressure (\(K_p\)).

Key concepts

Temperature dependence of equilibrium

The equilibrium constant, a fundamental concept in chemistry, plays a crucial role in determining the concentration of reactants and products in a chemical reaction at equilibrium. However, this constant is not fixed and can vary with changes in temperature. Temperature affects how reactants and products interact during a chemical reaction, which in turn affects the equilibrium position.
When temperature changes, the balance between the forward and reverse reactions can shift. According to Le Chatelier's principle, if you increase the temperature, the equilibrium will shift in the direction that absorbs heat, while a decrease in temperature will shift it towards the reaction that releases heat. This essentially means that the equilibrium constant (\(K\)) will change based on the temperature because the rates of both forward and reverse reactions are temperature dependent.

• In exothermic reactions, increasing the temperature causes the equilibrium constant to decrease.
• Conversely, in endothermic reactions, increasing temperature results in an increase in the equilibrium constant.

Therefore, knowing the temperature at which an equilibrium constant is calculated is vital as it helps to compare it accurately with the equilibrium constants calculated at other temperatures.

Stoichiometry of reactions

Stoichiometry refers to the quantitative relationship between the reactants and products in a chemical reaction. Understanding stoichiometry is essential for figuring out how compounds interact during a chemical reaction to achieve balance.
A balanced chemical equation provides a clear picture of the stoichiometry of the reaction. It shows the ratio of molecules and moles of reactants transforming into products. Without this information, it is difficult to comprehend the full scope of the reaction, or how equilibrium is achieved.

• Stoichiometry helps determine the proportion of substances needed for complete reactions.
• It allows us to calculate concentrations and partial pressures, which are critical for understanding the equilibrium state.

Since the equilibrium constant is derived from the concentrations of reactants and products at equilibrium, knowing the stoichiometry will enable us to grasp how substances change and redistribute in a reaction system.

Partial pressure and concentration in equilibrium

In chemical reactions involving gases, equilibrium can be described using two main measurements: partial pressures and molar concentrations. Understanding the difference between these two forms of expression is essential to accurately interpret the equilibrium constant, which can be represented as either (\(K_c\)) or (\(K_p\)).
Partial pressure refers to the pressure exerted by a single type of gas in a mixture of gases. It is an important measure for gases because it helps to determine each gas's individual contribution to the total pressure of the system. On the other hand, molar concentration measures how many moles of a substance are present in a given volume.

• (\(K_p\)) is used when the equilibrium constant is expressed in terms of partial pressures.
• (\(K_c\)) is used when the constant is expressed in terms of molar concentrations.

Being clear about which of these expressions is used makes a big difference in understanding the dynamics of the equilibrium state. This clarity can prevent confusion and inaccurate calculations when analyzing or predicting reactions.