S4 Pure Chemistry Extra Planning Revision 2024 Prelim

MGS 2024: In another experiment, the solubility of the organic acid, C, in different solvents, water, ethanol and acetone is investigated. Plan an investigation to find the effect of the nature of solvent on the solubility of the organic acid, C. You may assume the apparatus normally found in the school laboratory is available for the investigation. Outline: Variables / Conditions to be controlled: 1m Volume of solvent, temperature, speed of stirring, dry beaker Independent variable: type of solvent: 1m Dependent variable: maximum mass of the organic acid that has dissolved: 1m Add a known mass of the solid organic acid + stir to dissolve completely: 1m Continue adding until no more of the solid organic acid dissolves: 1m SST 2024: Iron nails rust in the presence of air and water. Iron nails can be coated with more reactive metals to protect them from rusting, through sacrificial protection. You have been given two unknown metals, A and B. These metals are either more or less reactive than iron. You are to outline a method to determine which metal A or B is more suitable to be used as a coating for the iron nails. You can assume that all apparatus and reagents normally found in a school laboratory are available. In your method you should note any assumptions that you make, include the observations you would record and explain how you would use your results to determine the metal to be used as a coating for the iron nails. Outline: 1. Set up two test tubes each with 25.0 cm3 of water inside. 2. Put one nail in each test tube, with metal A in the first test tube and metal B in the second test tube. 3. Leave both test tubes overnight and observe if each nail had any presence of rust. 4. Should there be a presence of rust in the nail, the metal coating protecting the nail is less reactive than iron. If there is no rust on the nail, the metal is more reactive than iron. Independent variable: metals A and B Dependent variable: presence of rust on nails Assumptions:

Each nail was rust-free before the start of the experiment. There are no impurities in metal coating provided. Nan Hua 2024 When an iron(III) sulfate sample crystallises from aqueous solution, it forms a trihydrated solid, Fe2(SO4)3.3H2O, which contains three molecules of water of crystallization per formula. Describe a method to show by experiment that the crystallised solid is a trihydrated solid. This method must not involve titration. You can assume all the apparatus and reagents normally found in a school laboratory are available. You should include any measurements you would take and explain how you would use your results to confirm that it is a trihydrated solid. [Ar: Fe, 56; S, 32; O, 16; H, 1] 1. Measure 1 g of the trihydrated solid (Fe2(SO4)3.3H2O) using an electronic balance. 2. Heat the trihydrated salt in a boiling tube until no change in mass. 3. Measure the mass of the anhydrous salt using the electronic balance and