Le Chatelier's principle

Which change would shift the position of this equilibrium towards the products? $\ce{H2(g) + I2(g) <=> 2HI(g)}$ $\Delta H = -9\ \mathrm{kJ\,mol^{-1}}$ A. Increase pressure B. Decrease pressure C. Increase temperature D. Decrease temperature

The amount of $\ce{NO2}$ prepared was checked by titration. The gas was first absorbed in water: $\ce{2NO2(g) + H2O(l) -> HNO3(aq) + HNO2(aq)}$ The resulting solution was made up to 200.0 $\mathrm{cm^3}$ in a volumetric flask, and 20.0 $\mathrm{cm^3}$ portions…

Cresolphthalein is a weak acid that can be represented as HIn. Using an equation, explain why the colour of a solution containing cresolphthalein depends on its pH.

When potassium thiocyanate solution is added to a pale yellow solution containing iron(III) ions, the following equilibrium is established. $\ce{[Fe(H2O)6]^3+(aq) + SCN^-(aq) <=> [Fe(SCN)(H2O)5]^2+(aq) + H2O(l)}$ $\ce{[Fe(H2O)6]^3+(aq)}$ is pale yellow and…

(i) An equilibrium mixture in a 25.0 $\mathrm{dm^3}$ reactor at 500 °C contains 15.0 mol $\ce{N2}$, 22.5 mol $\ce{H2}$ and 5.25 mol $\ce{NH3}$. Calculate the equilibrium constant, $K$, for the reaction. (ii) The volume of the reactor containing the equilibrium…

The gas-phase decomposition below has reached equilibrium in a sealed vessel: $\ce{PCl5(g) <=> PCl3(g) + Cl2(g)}$ $\Delta H^\ominus = +88\ \mathrm{kJ\,mol^{-1}}$ The pressure is then changed. Which row pairs the change correctly with the direction in which the…

Iron(III) ions and thiocyanate ions form a deep red complex ion in aqueous solution. $\ce{Fe^3+(aq) + SCN^-(aq) <=> [Fe(SCN)]^2+(aq)}$ Which of the following correctly predicts the effect of a change on this equilibrium? A. Adding iron(III) nitrate solution…

The container holding the equilibrium mixture below is compressed to half its volume while the temperature is kept constant. Which row gives the change in the amount of $\ce{PCl5}$ and the effect on the equilibrium constant, $K$?…

(i) Sketch the Maxwell–Boltzmann distribution curve for 298 K on the same axes as the 800 K curve. (ii) On the graph, annotate the position corresponding to the activation energy, $E_\mathrm{a}$. (iii) With reference to the graph, explain why a lower…

The pool operators add sodium carbonate to the water to raise its pH. Explain why a larger proportion of the dissolved chlorine reacts with water after the sodium carbonate has been added.

A student writing a report on chlorine as a disinfectant collects, from several websites and reference books, values for how much chlorine dissolves in pure water at various temperatures. Source Temperature / °C Solubility of chlorine A 5 1.18 g per 100…

Some users have asked for the water to be heated in winter. Suggest two reasons why leaving the water unheated is the better choice for the environment.

Suggest two reasons why less carbon dioxide is collected in the syringe when a greater mass rests on the piston.

The equilibrium constant, $K_\mathrm{c}$, for the reaction in (f) is $6.4 \times 10^{-5}$ at 80 °C. (i) $1.00\ \mathrm{dm^3}$ of a mixture that is initially $0.20\ \mathrm{mol\,dm^{-3}}$ in octadecanoic acid and $0.20\ \mathrm{mol\,dm^{-3}}$ in butan-2-ol is…

An indicator, HIn, is a weak acid with $\mathrm{p}K_a = 5.0$. HIn is yellow and its conjugate base, $\ce{In-}$, is blue. $\ce{HIn(aq) <=> H+(aq) + In^-(aq)}$ Which statements are correct? I. At pH 2.0 the indicator appears yellow. II. At pH 5.0 the…