In the laboratory, hydrogen chloride gas is produced by adding concentrated sulfuric acid to potassium chloride. Write an equation for this reaction.
Explain why hydrogen iodide is not made by adding concentrated sulfuric acid to sodium iodide.
A sample of $\\text{HI(g)}$ is placed in a sealed $2.00\\,\\text{dm}^3$ vessel at $764\\,\\text{K}$ and left until equilibrium is reached.\n\nReaction 1:\n$2\\text{HI(g)} \\rightleftharpoons \\text{H}_2\\text{(g)} + \\text{I}_2\\text{(g)}$ with $K_c = 0.0217$ at $764\\,\\text{K}$.\n\nAt equilibrium the mixture contains $1.70\\,\\text{mol}$ of $\\text{HI(g)}$.\n\nState one difference in appearance between the initial mixture and the mixture at equilibrium.
Deduce the equilibrium constant expression $K_c$ for reaction 1.\n\n$K_c =$
Calculate the concentration of $\\text{I}_2$ in the equilibrium mixture. Show your working.
The experiment is carried out again at $500\\,\\text{K}$. Under these conditions, $K_c$ is $0.00625$. Describe how the composition of the equilibrium mixture at $500\\,\\text{K}$ differs from that at $764\\,\\text{K}$.
Use Le Chatelier’s principle to decide whether the decomposition of $\\text{HI(g)}$ is endothermic or exothermic. Explain your answer.