Nernst equation for the reaction
`aA+bBoverset("ne"-)rarr cC+ dD` is
`E_(cell)=E_(cell)^(@)-(RT)/(nF) "ln" Q`
what is Q in the Nernst equation

Options

A. `([A]^(a)[B]^(b))/([C]^(c )[D]^(d))`
B. `([A]^(a)[D]^(d))/([B]^(b )[C]^(C ))`
C. `([C]^(c )[D]^(d))/([A]^(a)[B]^(b))`
D. `([C ]^(c)[A]^(a))/([D]^(d)[B]^(b))`

Explanation

To solve the question about the Nernst equation and specifically what Q represents, we can break it down into the following steps:

### Step 1: Understand the Nernst Equation
The Nernst equation is given as:
\[ E_{cell} = E_{cell}^\circ - \frac{RT}{nF} \ln Q \]
Where:
- \( E_{cell} \) = cell potential under non-standard conditions
- \( E_{cell}^\circ \) = standard cell potential
- \( R \) = universal gas constant (8.314 J/(mol·K))
- \( T \) = temperature in Kelvin
- \( n \) = number of moles of electrons transferred in the reaction
- \( F \) = Faraday's constant (approximately 96485 C/mol)
- \( Q \) = reaction quotient

### Step 2: Define the Reaction Quotient (Q)
The reaction quotient \( Q \) is a measure of the relative amounts of products and reactants present in a reaction at any point in time. It is defined for a general reaction:
\[ aA + bB \rightleftharpoons cC + dD \]
as:
\[ Q = \frac{[C]^c [D]^d}{[A]^a [B]^b} \]

### Step 3: Identify the Components of Q
In the expression for \( Q \):
- The concentrations of the products (C and D) are raised to the power of their coefficients in the balanced equation.
- The concentrations of the reactants (A and B) are also raised to the power of their coefficients.
- \( [C] \), \( [D] \), \( [A] \), and \( [B] \) represent the molar concentrations of the respective species.

### Step 4: Distinguish Between Q and K
It is important to note that:
- \( Q \) can be calculated at any point during the reaction, regardless of whether the system is at equilibrium.
- When the system reaches equilibrium, \( Q \) becomes the equilibrium constant \( K \).

### Final Answer
Thus, in the context of the Nernst equation, \( Q \) is the reaction quotient, which is calculated as:
\[ Q = \frac{[C]^c [D]^d}{[A]^a [B]^b} \]