Calculate Kp from Kc.
Understand the Problem
The question is asking how to convert the equilibrium constant in concentration terms (Kc) to the equilibrium constant in pressure terms (Kp). This involves understanding the relationship between Kp and Kc, typically expressed by the equation Kp = Kc(RT)Δn, where R is the gas constant, T is the temperature in Kelvin, and Δn is the change in the number of moles of gas during the reaction.
Answer
$$ K_p = K_c(RT)^{\Delta n} $$
Answer for screen readers
$$ K_p = K_c(RT)^{\Delta n} $$
Replace $K_c$, $R$, $T$, and $\Delta n$ with the specific values to find the final answer.
Steps to Solve
- Understand the relationship between Kp and Kc
To convert from Kc to Kp, we use the formula:
$$ K_p = K_c(RT)^{\Delta n} $$
where:
- $R$ is the universal gas constant (0.0821 L·atm/(K·mol)),
- $T$ is the temperature in Kelvin,
- $\Delta n$ is the change in moles of gas, which is calculated by subtracting the moles of gaseous products from the moles of gaseous reactants.
- Determine the change in moles of gas ($\Delta n$)
You can find $\Delta n$ from the balanced chemical equation. For example, for the reaction:
$$ aA(g) + bB(g) \rightleftharpoons cC(g) + dD(g) $$
The change in moles of gas is calculated as:
$$ \Delta n = (c + d) - (a + b) $$
- Calculate Kp
Once you have Kc, R, T, and $\Delta n$, plug these values into the equation:
$$ K_p = K_c(RT)^{\Delta n} $$
Perform the calculations step by step to get the value of Kp.
$$ K_p = K_c(RT)^{\Delta n} $$
Replace $K_c$, $R$, $T$, and $\Delta n$ with the specific values to find the final answer.
More Information
The relationship between Kc and Kp helps chemists understand how changes in temperature and pressure affect chemical equilibria. This is especially important in physical chemistry and chemical engineering.
Tips
- Incorrectly calculating $\Delta n$: Ensure to properly count moles of gaseous reactants and products.
- Using the wrong units for R or T: Make sure R is in the proper units and T is in Kelvin.
- Not recognizing that Kp and Kc are temperature-dependent: Kp and Kc values change with temperature, so ensure you are using the correct temperature for the calculation.
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