Zadania z chemii IB HL

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.