Zadania z chemii IB HL

Explain why the start line must be horizontal and must be above the level of the solvent when the strip is placed in the chamber.

Explain how the dyes are separated from one another in paper chromatography.

Describe the steps the student would follow to recrystallize the crude benzoic acid.

State the most important property that water must have, with respect to benzoic acid, for it to be a suitable solvent for this recrystallization.

Outline how each of the two by-products is removed from the benzoic acid during the recrystallization. By-product that is almost insoluble in hot water: ... By-product that is much more soluble than benzoic acid: ...

The volume of hot water used to dissolve the crude solid must be chosen carefully. Deduce the effect on the yield or on the purity of the recrystallized benzoic acid of using too much water and of using too little water. Too much water: ... Too little water:…

Describe the setup that would connect the $\ce{Sn^4+}/\ce{Sn^2+}$ half-cell to a second half-cell for comparing the two electrode potentials.

Most pools, including this lido, are dosed with sodium hypochlorite solution, $\ce{NaOCl(aq)}$, instead of chlorine gas. Suggest why pool operators avoid dosing the water with chlorine gas itself.

The student measures the hydrogensulfite concentration by titrating samples against a standard iodine solution, with starch as the indicator. Every three days, 25.00 $\mathrm{cm^3}$ of cordial is withdrawn from each flask, diluted to 250.0 $\mathrm{cm^3}$ with…