Record qualitative and quantitative data in tables with headings and units, process them with correct significant figures and uncertainties, and present them in graphs that support the conclusion.
Tę umiejętność sprawdzają 34 zadania wzorowane na arkuszach IB z lat 2023–2026.
(a) The graph shows how the water level of the Salton Sea has changed since 1950. The reference point for the water level is sea level. (i) Suggest a reason why the values plotted on the vertical axis are negative. (ii) Describe the general trend in the rate…
Suggest how the total quantity of light emitted in each run could be obtained from the graph.
Explain how the rate at which the light intensity was falling after 15 minutes in the 44.8 °C run could be determined from the graph.
The graph shows the maximum rate of decrease in light intensity for each run, plotted against temperature. (i) Draw the best-fit curve on the graph. (ii) Suggest two possible conclusions that can be drawn from the investigation.
Calculate the change in temperature for trial 5 and its uncertainty. Give the temperature change to a suitable number of decimal places and the uncertainty to a suitable number of significant figures.
Determine the mean specific energy of ethanol from the five trials, explaining your method. If you did not obtain an answer to (c), use 8000 J g−1 for trial 5; this is not the correct value.
Before the samples were measured, an absorption spectrum was recorded to find the best wavelength to use. (i) Describe the contents of the two solutions required to record the spectrum: the reference solution and the blank. (ii) The spectrum obtained is shown.…
Colorimetry is an alternative technique for determining concentration. Iron(II) ions can be converted to a red complex ion by adding 1,10-phenanthroline. (i) Outline why the concentration of iron(II) in a solution can be measured by colorimetry after this…
Explain how the calibration curve is then used to determine the concentration of KMnO4 in a reaction mixture of unknown concentration.
Each student used a different mass of the hydrated salt. The results of the whole class are shown below (Mr of H2O = 18.02). (i) Determine the two missing values in the table. The class results were plotted on the graph below. (ii) Draw a line of…
Bathers release nitrogen-containing compounds, including ammonia, into the pool water. Ammonia reacts with hypochlorous acid to form chloramines. (i) Deduce an equation for the reaction of ammonia with hypochlorous acid that forms trichloramine,…
The following burette readings are recorded in one of the titrations. Final burette reading = 26.15 ± 0.05 cm3 Initial burette reading = 1.15 ± 0.05 cm3 Calculate the percentage uncertainty in the titre volume.
Use the volumes collected at 120 s in Experiment 1 and Experiment 3 to calculate by what percentage the final volume of carbon dioxide falls for each 100 g added to the piston.
The data for 0.6 g of catalyst seem anomalous. Suggest a possible cause.
The results in Figure 1 were processed to give Figure 2, which shows how the initial rate of reaction varies with the mass of catalyst. (i) Outline how the y-axis values in Figure 2 were obtained from the results in Figure 1. (ii) Suggest, giving a reason,…
The concentration of hydrogen peroxide in a reaction mixture was followed for 600 s and the results are plotted in the graph. (i) Determine the instantaneous rate of the reaction, to two significant figures, when [H2O2] = 0.160 mol dm−3.…
The uncertainty in each mass reading is ±0.04 g. (i) Calculate the percentage uncertainty in the total mass loss. (ii) Using your answer to (i), calculate the absolute uncertainty in the number of moles of water per mole of MgSO4, that is the…
Two methods of making ethyl ethanoate are compared using the Eco-Scale. The penalty points are given in the table. Method 1: ethanoic acid reacts with ethanol, with concentrated sulfuric acid as the catalyst. The mixture is heated in a microwave reactor for 40…
The student then followed the reaction with a spectrophotometer, which records the light absorbed by the mixture and so gives the concentration of the dye throughout the reaction. The graph shows [D+] against time for experiment 3. (i) Use the graph to…
Young mussels were placed in a contaminated harbour. Samples were taken at regular intervals and the tin content of the soft tissue was determined. (i) The tin content follows a linear trend during the first six weeks. Deduce the equation for this part of the…
The concentration of tin in a sample of mussel tissue is 0.0064 ± 0.0002 mg Sn g−1. (i) Calculate the mass of tin, in mg, in 2.416 g of the sample. (ii) Calculate the percentage uncertainty of the concentration.
(i) State which two further mass measurements are needed to find the oxide composition. (ii) Outline how these measurements give the mass of oxygen removed from the sample.
A conductivity probe is used to follow the concentration of sodium chloride in dilute aqueous solutions. A solution of concentration 0.015 mol dm−3 gives a conductivity of 1.8 mS cm−1. On the axes, draw a graph of conductivity…
The concentration of copper(II) ions in wastewater from a plating works was determined by colorimetry. Excess ammonia solution was added to each solution so that all the copper(II) ions formed the deep blue complex ion [Cu(NH3)4]2+, and the absorbance…
The concentration of copper(II) ions in a sample of pond water is determined with a colorimeter. The absorbance of standard solutions of known concentration is measured and a calibration curve is plotted. Sketch the typical shape of the calibration curve on…
A student prepared standard solutions of copper(II) sulfate and measured the absorbance of each with a colorimeter. The graph shows the calibration line. A sample of copper(II) sulfate solution of unknown concentration has an absorbance of 0.600. State its…
The rate constant, k, for the alkaline hydrolysis of ethyl ethanoate was determined at several temperatures. The processed data are shown in the graph. Determine the activation energy for this reaction, stating the units. Use sections 1 and 2 of the data…
Determine the identity of the amino acid in spot B by calculating its RF value from the chromatogram.
Heat treatment at 90 °C is used to destroy spoilage micro-organisms in pineapple juice. The concentration of vitamin C was measured over 56 days in untreated juice and in heat-treated juice from the same batch. (i) Identify the dependent variable in this…
The concentration of vitamin C and the pH of five fruit juices were measured. Use the data to deduce whether pH and the concentration of vitamin C are correlated, giving a reason.
(i) Identify the dependent variable plotted on the graph. (ii) Calculate the decrease in the concentration of vitamin C, in μg cm−3, caused by the heat treatment. (iii) Calculate the average rate of decrease of the vitamin C concentration in…
The concentration of vitamin C and the pH of juice from five different fruits were measured. Deduce, with a reason, whether the data show a correlation between the concentration of vitamin C and pH.
The concentration of protein in an extract can be found by mixing it with a dye that binds to protein and measuring the absorbance at 595 nm. The calibration line for standard protein solutions is shown. Its equation is y = 0.2903x + 0.0090, where y is the…
The concentration of protein in egg white was determined by a dye-binding method. The absorbance at 595 nm of protein solutions of known concentration was used to draw a calibration line, with the equation shown. Calculate, using the linear equation, the…
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