Chemistry HL Paper 1B, November 2025, TZ1

Calculate the mass of solid potassium hydroxide that has to be weighed out.

Describe how the student should prepare this standard solution from the weighed solid using a 250.0 $\mathrm{cm^3}$ volumetric flask.

The student pipetted 25.00 $\mathrm{cm^3}$ of the potassium hydroxide solution into a conical flask and titrated it with nitric acid, $\ce{HNO3(aq)}$, of concentration 0.1250 $\mathrm{mol\,dm^{-3}}$. The burette readings before and after the titration are…

Using the concentration determined in 1c and the intended concentration of 0.1500 $\mathrm{mol\,dm^{-3}}$, calculate the percentage error in the concentration of the potassium hydroxide solution. If you have no value from 1c, take the concentration to be…

Explain why the potassium hydroxide solution has to be standardized before it is used in the titration. Assume that there are no systematic errors in the procedure.

The student then used the potassium hydroxide solution standardized in 1c to titrate ethanoic acid, $\ce{CH3COOH}$, whose concentration was not known. (i) Neutralizing 25.00 $\mathrm{cm^3}$ of the acid required 40.00 $\mathrm{cm^3}$ of the standardized…

Using sections 1 and 2 of the data booklet, determine the amount of heat that the water in beaker B gained from the metal.

Assume that the heat released by the metal is equal to the heat absorbed by the water in beaker B, calculated in 2a. Determine the specific heat capacity of the metal. Use section 1 of the data booklet. If you have no answer to 2a, take the heat transferred to…

Using the table below, state the name of the metal from which the block is made. Metal Specific heat capacity / $\mathrm{J\,g^{-1}\,K^{-1}}$ Tin 0.228 Zinc 0.388 Titanium 0.523 Magnesium 1.02

Deduce, from the results obtained, two sources of systematic error in this procedure.

State one other physical property that could be measured to identify the metal while leaving the block intact.

Each beaker used as a chromatography chamber was covered with a watch glass while the solvent rose up the paper. Explain why the chamber has to be covered for the experiment to be properly designed.

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.

For the orange dye, calculate the retardation factor, $R_\mathrm{F}$, obtained in each solvent system. Dye $R_\mathrm{F}$ Orange dye, system 1 (25 % ethanol) Orange dye, system 2 (75 % ethanol)

Deduce, giving a reason, which of the two dyes, orange or violet, is the more polar.

The student suspected that the ink contained more than four dyes, and that one of the spots was two dyes that had not separated. Suggest how the student could modify the chromatography experiment to test this idea.

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