The equilibrium constant of a chemical reaction

Options

A. is constant at a given temperature
B. has only numerical value and carries no units
C. its value always depends upon the units in which the concentrations of species involved in chemical reaction are measured
D. changes if the sioichiometric coofficients of all the species involved in the chemical equation are changed

Answer

To solve the question regarding the equilibrium constant of a chemical reaction, we will analyze the statements provided and determine their validity step by step.

### Step 1: Understand the Definition of Equilibrium Constant
The equilibrium constant (K_eq) is a numerical value that expresses the ratio of the concentrations of products to the concentrations of reactants at equilibrium for a given chemical reaction at a specific temperature.

**Hint:** Remember that K_eq is defined based on the balanced chemical equation.

### Step 2: Analyze the First Statement
The first statement claims that the equilibrium constant is constant at a given temperature. This is true. The value of K_eq does not change unless the temperature changes.

**Hint:** Consider how temperature affects chemical reactions and their equilibria.

### Step 3: Analyze the Second Statement
The second statement asserts that the equilibrium constant has only a numerical value and carries no unit. This statement is incorrect. The equilibrium constant can have units depending on the reaction and the concentrations of the species involved.

**Hint:** Think about how concentrations are expressed in molarity (M) and how this affects the units of K_eq.

### Step 4: Analyze the Third Statement
The third statement states that the value of the equilibrium constant always depends on the units in which the concentrations of species involved in the chemical reaction are measured. This statement is true. The units can vary based on the stoichiometry of the reaction.

**Hint:** Reflect on how different concentration units can lead to different representations of K_eq.

### Step 5: Analyze the Fourth Statement
The fourth statement claims that the equilibrium constant changes if the stoichiometric coefficients of all species involved in the chemical equations are changed. This statement is incorrect. The equilibrium constant is derived from the balanced chemical equation, and changing the coefficients alters the expression of K_eq, but it does not change the constant itself for the same reaction.

**Hint:** Consider the importance of a balanced equation in determining K_eq.

### Conclusion
After analyzing all the statements:
- The first statement is **true**.
- The second statement is **false**.
- The third statement is **true**.
- The fourth statement is **false**.

Thus, the correct statements are the first and third.

**Final Answer:** The correct statements are A and C.