Chemistry 2025 · May/June

Activated carbon is a form of carbon with the ability to adsorb solutes from solutions. The adsorption of ethanedioic acid molecules, (COOH) , from dilute ethanedioic acid, (COOH)

, onto the surface of activated carbon is studied in a series of experiments. Before beginning the experiment, 500.0 cm of 0.139 mol dm (COOH)

, solution X, is made. The activated carbon is placed in an oven at 120 °C for three hours. The experimental procedure involves the following steps. step 1 Prepare 100.0 cm of 0.00556 mol dm (COOH)

from solution X. step 2 Transfer 50.0 cm of the 0.00556 mol dm (COOH)

into a conical flask. step 3 Add 0.500 g of activated carbon to the conical flask and start a stopwatch. step 4 Shake the flask and immediately remove a 5.0 cm sample from the flask. Determine the mass of non-adsorbed (COOH) in the sample using chromatography. step 5 Repeat step 4 at suitable time intervals until there is no further change in the mass of non-adsorbed (COOH) in the sample.

Solid ethanedioic acid has the formula (COOH)

Calculate the mass of (COOH) O

required to prepare 500.0 cm of 0.139 mol dm (COOH)

, solution X. mass = g

The mass of (COOH) O

calculated in

Give the name and capacity of any apparatus used. Write your answer using a series of numbered steps.

(COOH) O

is corrosive. Other than wearing eye protection and a lab coat, state one safety precaution that should be taken when using (COOH) O

Suggest why the activated carbon is placed in the oven before use.

In step 1, solution X is diluted to a concentration of 0.00556 mol dm Calculate the volume of solution X needed to make 100.0 cm of 0.00556 mol dm (COOH)

volume of solution X = cm

Identify the most appropriate piece of equipment to transfer 50.0 cm of diluted (COOH)

in step 2.

Suggest a reason why the conical flask is shaken in step 4.

The results of the experiment are shown in Table 1.1. Table 1.1 time, t / min mass of non-adsorbed (COOH) in 5.0 cm sample / mg mass of (COOH) adsorbed by activated carbon in 5.0 cm sample / mg 0 2.50 0.00 5 1.90 15 1.52 30 1.43 45 0.99 60 0.88 90 0.81 120 0.80 150 0.80

Complete T able 1.1.

Plot a graph on the grid in Fig. 1.1 to show the relationship between mass of (COOH) adsorbed by activated carbon in 5.0 cm sample and time, t. Use a cross (×) to plot each data point. Draw a curved line of best fit.

Identify the independent variable.

Suggest one variable that needs to be controlled that is not stated in the experimental procedure.

Circle the one point on the graph that you consider to be most anomalous. Explain the error in timing that may have led to this anomalous point. 0.2 0 20 40 60 80 time, t / min mass of (COOH) adsorbed by activated carbon in 5.0 cm sample / mg 100 120 140 160 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 Fig. 1.1 * 0000800000005 *

The experiment is repeated using dif ferent concentrations of (COOH)

prepared in step 1. The results are shown in Table 1.2. Table 1.2 1 2 3 4 5 / mg m / mg (m- m ) / mg q / mg g -1 m 2.5 0.80 1.70 34.0 0.0235 5.0 2.10 2.90 58.0 0.0362 7.5 4.03 3.47 69.4 0.0581 10.0 6.41 3.59 71.8 0.0893 12.5 8.87 3.63 72.6 0.1222 is the initial mass of (COOH) in 5.0 cm sample. is the mass of non-adsorbed (COOH) in the final 5.0 cm sample at the end of step 5. is the mass of (COOH) adsorbed per gram of activated carbon.

A plot of against m gives the line of best fit shown in Fig. 1.2. Use Fig. 1.2 to determine the gradient of the line of best fit. State the coordinates of both points you used in your calculation. coordinates 1 coordinates 2 Include units in your answer. gradient = units =

The adsorption parameter , q , is the maximum mass of (COOH) adsorbed per gram of activated carbon. The equation of the line of best fit plotted in Fig. 1.2 is shown. + constant Use the gradient determined in

, then use the value 0.0136 for the gradient. This is not the correct answer.] = mg g [1] * 0000800000006 * 0.02 0 2 4 6 8 / mg/ g 0.04 0.06 0.08 0.10 0.12 0.14

The experiment is repeated and the value of q is calculated to be 78.1 mg g . The total percentage error from the experimental procedure is 6.5%. The data book value of q is 86.0 mg g Use this information to determine whether the error in the repeated experiment could be accounted for by experimental errors or is caused by other factors. Show your working. [Total: 20] * 0000800000007 * , of butane, C , can be determined using the apparatus shown in Fig. 2.1. metal can thermometer watertap gas container of butane tripod gas burner The following steps are carried out. step 1 Use a 500 cm measuring cylinder to transfer 320 cm of water into a metal can. step 2 Place a thermometer into the water . Record the initial temperature of the water in the metal can. step 3 Weigh the gas container with burner and record the initial mass. step 4 Set up the apparatus as shown in Fig. 2.1. step 5 Light the burner and allow the flame to heat the water in the metal can for three minutes. step 6 Switch off the burner and record the maximum temperature reached. step 7 When cool, reweigh the gas container with burner and record the final mass. The results are shown in Table 2.1. Table 2.1 initial temperature of water / °C maximum temperature of water / °C change in temperature of initial mass of gas container with burner / g final mass of gas container with burner / g mass of butane burned / g 19.3 76.6 183.56 181.46

Complete Table 2.1. Record your answers to the appropriate number of decimal places. [2] * 0000800000008 * 1.00 cm of water has a mass of 1.00 g. q = J [1] , of butane, in kJ mol Give your answer to three significant figures. = kJ mol

Without changing the apparatus, suggest what should be done in step 6 before recording the maximum temperature reached to improve the experimental procedure.

The 500 cm measuring cylinder has graduations every 5 cm Calculate the percentage error in the measurement of the volume of water . Show your working. percentage error = % [1] of butane because of heat lost during the experiment. Suggest one change to the apparatus that would reduce the heat lost.

The experiment was repeated but the burner was switched of f after only two minutes. of butane. of butane. [Total: 10] * 0000800000009 * BLANK PAGE * 0000800000010 * Important values, constants and standards molar gas constant R = 8.31 J Kmol Faraday constant F = 9.65 × 10 C mol Avogadro constant L = 6.02 × 10mol electronic charge e = -1.60 × 10-19 molar volume of gas V = 22.4 dmmol at s.t.p. (101 kPa and 273 K) = 24.0 dmmol at room conditions ionic product of water K = 1.00 × 10-14mol (at 298 K (25 °C)) (4.18 J g ) * 0000800000011 * To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge Assessment International Education Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cambridgeinternational.org after the live examination series. Group The Periodic Ta ble of Elements hydrogen 1.0 helium 4.0 12 13 14 15 16 17 18 3456789 10 11 12 lithium 6.9 beryllium 9.0 atomic number atomic symbolKey name relative atomic mass sodium 23.0 magnesium 24.3 potassium 39.1 calcium 40.1 rubidium 85.5 strontium 87.6 caesium 132.9 barium 137.3 francium radium boron 10.8 aluminium 27.0 gallium 69.7 indium 114.8 thallium 204.4 carbon 12.0 silicon 28.1 germanium 72.6tin 118.7 lead 207.2 titanium 47.9 zirconium 91.2 hafnium 178.5 rutherfordium vanadium 50.9 niobium 92.9 tantalum 180.9 dubnium chromium 52.0 molybdenum 95.9 tungsten 183.8 seaborgium manganese 54.9 technetium rhenium 186.2 bohrium iron 55.8 ruthenium 101.1 osmium 190.2 hassium cobalt 58.9 rhodium 102.9 iridium 192.2 meitnerium nickel 58.7 palladium 106.4 platinum 195.1 darmstadtium copper 63.5 silver 107.9 gold 197.0 roentgenium zinc 65.4 cadmium 112.4 mercury 200.6 copernicium flerovium livermorium nitrogen 14.0 phosphorus 31.0 arsenic 74.9 antimony 121.8 bismuth 209.0 oxygen 16.0 sulfur 32.1 selenium 79.0 tellurium 127.6 polonium fluorine 19.0 chlorine 35.5 bromine 79.9 iodine 126.9 neon 20.2 argon 39.9 krypton 83.8 xenon 131.3 radon nihonium moscovium tennessine oganesson scandium 45.0 yttrium 88.9 57-71 lanthanoids 89-103 actinoids lanthanum 138.9 lanthanoids actinoids actinium cerium 140.1 thorium 232.0 praseodymium 140.9 protactinium 231.0 neodymium 144.2 uranium 238.0 promethium neptunium samarium 150.4 plutonium europium 152.0 americium gadolinium 157.3 curium terbium 158.9 berkelium dysprosium 162.5 californium holmium 164.9 einsteinium erbium 167.3 fermium thulium 168.9 mendelevium ytterbium 173.1 nobelium lutetium 175.0 lawrencium - * 0000800000012 *