Nitrogen dioxide gas is heated in a sealed container at 700 K until the system comes to equilibr

Nitrogen dioxide gas is heated in a sealed container at 700...

Nitrogen dioxide gas is heated in a sealed container at $700 \mathrm{K}$ until the system comes to equilibrium. The nitrogen dioxide dissociates into nitrogen monoxide and oxygen in an endothermic process (Section $1.9)$ $$2 \mathrm{NO}_{2}(\mathrm{g}) \rightleftharpoons 2 \mathrm{NO}(\mathrm{g})+\mathrm{O}_{2}(\mathrm{g})$$ The equilibrium constant at $700 \mathrm{K}$ is $2.78 \times 10^{-2} \mathrm{moldm}^{-3}$ (a) Write an expression for $K_{c}$ (b) State how the position of equilibrium would be affected by: (1) an increase in temperature (ii) an increase in the total pressure. (c) At equilibrium at $700 \mathrm{K}$, the concentration of nitrogen monoxide was found to be $0.017 \mathrm{moldm}^{-3}$. What was the concentration of nitrogen dioxide in the equilibrium mixture?

Nitrogen dioxide gas is heated in a sealed container at $700 \mathrm{K}$ until the system comes to equilibrium. The nitrogen dioxide dissociates into nitrogen monoxide and oxygen in an endothermic process (Section $1.9)$ $$2 \mathrm{NO}_{2}(\mathrm{g}) \rightleftharpoons 2 \mathrm{NO}(\mathrm{g})+\mathrm{O}_{2}(\mathrm{g})$$ The equilibrium constant at $700 \mathrm{K}$ is $2.78 \times 10^{-2} \mathrm{moldm}^{-3}$
(a) Write an expression for $K_{c}$
(b) State how the position of equilibrium would be affected by:
(1) an increase in temperature
(ii) an increase in the total pressure.
(c) At equilibrium at $700 \mathrm{K}$, the concentration of nitrogen monoxide was found to be $0.017 \mathrm{moldm}^{-3}$. What was the concentration of nitrogen dioxide in the equilibrium mixture?

Key Concepts

Chemical Equilibrium

Chemical equilibrium refers to the state in which reactants and products are formed at the same rate and their concentrations remain constant over time. In this state, the forward reaction proceeds at the same rate as the reverse reaction, even though both reactions continue to occur continuously.

Equilibrium Constant Expression (Kc)

The equilibrium constant, Kc, is a numerical value that expresses the ratio of the concentrations of products to reactants, with each raised to the power of their respective stoichiometric coefficients. This expression only includes species in the gaseous or aqueous phases, and it quantitatively describes the position of equilibrium in a chemical reaction.

Le Chatelier's Principle

Le Chatelier's Principle states that if an external change is imposed on a system at equilibrium, the system will adjust its position to partially counteract the change. This principle is used to predict the direction in which the equilibrium will shift when conditions such as temperature, pressure, or concentration are altered.

Effect of Temperature on Equilibrium in Endothermic Reactions

For endothermic reactions, heat is absorbed as the reaction proceeds. Increasing the temperature adds more heat to the system, which, according to Le Chatelier's Principle, shifts the equilibrium towards the production of more products to absorb the excess heat. Conversely, lowering the temperature would shift the equilibrium towards the reactants.

Effect of Pressure on Gaseous Equilibria

For reactions involving gases, changes in the total pressure (or volume) can affect the equilibrium position. An increase in pressure generally favors the side of the reaction with fewer moles of gas, because the system adjusts in accordance with Le Chatelier's Principle to minimize the change in pressure. Conversely, a decrease in pressure favors the reaction side with more moles of gas.

Transcript

00:02 Given the following equilibrium, we have two no2 gas in equilibrium with 2 no gas and o2 gas.

00:15 And o2 gas for part a, we're asked to write the kc expression, products over reactants, this will be no squared, o2, coefficients become exponents, n02 squared, and there is our kc expression.

00:31 For b, how would the equilibrium be affected by one and increase in temperature? we're told that this is endothermic, so our enthalpy would be on the left -hand side here.

00:49 So if we increase the temperature, then that would result in the heat term increasing, and this would show a shift to the right.

01:01 So an increase in temperature would result in a shift towards the right or towards the products.

01:10 And for change number two, if we increase the total pressure, going back to our equilibrium here, if we increase the pressure, this side here would be our low pressure side as there are two moles of gas.

01:36 This side here would be our high pressure side, as there are three moles of gas.

01:40 Increase the pressure.

01:42 Lachiatide's principle would want to do the opposite.

01:43 It would want to bring the pressure back down to low.

01:46 So this would result in a shift towards the left or shift towards the reactants.

02:01 For part c, given that the nitrogen monoxide was drawn to be 0 .017 molar at equilibrium.

02:13 What was the concentration of nitrogen dioxide in the equilibrium mixture? so we'll set up an ice table here...

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