Consider the reaction: NH4HS(s) ⇌ NH3(g) + H2S(g). An equilibrium mixture of this reaction at a certain temperature has [NH3] = 0.278 M and [H2S] = 0.355 M. What is the value of the equilibrium constant (Kc) at this temperature?

Verified step by step guidance

Identify the balanced chemical equation: NH4HS(s) ⇌ NH3(g) + H2S(g).

Recognize that the equilibrium constant expression (Kc) for this reaction involves only the gaseous products, since solids are not included in the expression.

Write the expression for the equilibrium constant: Kc = [NH3][H2S].

Substitute the given equilibrium concentrations into the Kc expression: Kc = (0.278)(0.355).

Calculate the product of the concentrations to find the value of Kc.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Chemical Equilibrium

Chemical equilibrium occurs when the rates of the forward and reverse reactions are equal, resulting in constant concentrations of reactants and products. In this state, the system is dynamic, meaning that reactions continue to occur, but there is no net change in the concentrations of the substances involved.

Equilibrium Constant (Kc)

The equilibrium constant (Kc) is a numerical value that expresses the ratio of the concentrations of products to reactants at equilibrium, each raised to the power of their coefficients in the balanced equation. For the reaction NH4HS(s) ⇌ NH3(g) + H2S(g), Kc is calculated using the formula Kc = [NH3][H2S], as solids do not appear in the expression.

Concentration Units

Concentration is a measure of the amount of a substance in a given volume of solution, typically expressed in molarity (M), which is moles of solute per liter of solution. Understanding how to interpret and manipulate concentration values is essential for calculating equilibrium constants and analyzing chemical reactions.

Recommended video:

Guided course

02:13

SI Units

Related Practice

Textbook Question

Consider the reaction: N₂(g) + 3 H₂(g) ⇌ 2 NH₃(g) Complete the table. Assume that all concentrations are equilibrium concentrations in M.

T (K) [N₂] [H₂] [NH₃] K_c

500 0.115 0.105 0.439 _

575 0.110 _ 0.128 9.6

775 0.120 0.140 _ 0.0584

Textbook Question

Consider the following reaction: H₂(g) + I₂(g) ⇌ 2 HI(g) Complete the table. Assume that all concentrations are equilibrium concentrations in M.

T (°C) [H₂] [I₂] [HI] Kc

25 0.0355 0.0388 0.922 _

340 _ 0.0455 0.387 9.6

445 0.0485 0.0468 _ 50.2

Textbook Question

Consider the reaction: 2 NO(g) + Br₂(g) ⇌ 2 NOBr(g) K_p = 28.4 at 298K In a reaction mixture at equilibrium, the partial pressure of NO is 108 torr and that of Br₂ is 126 torr. What is the partial pressure of NOBr in this mixture?