8.1 Define an acid in terms of the Lowry-Brønsted theory. (2) 8.2 Consider the following acid-base reaction: H2PO4+ NH3 → HPO42- + NH4+ 8.2.1 Identify the conjugate acid-base pairs in the above reaction. (4) 8.2.2 Define the term ampholyte. (1) 8.2.3 Choose an ampholyte in the above reaction. (2) 8.3 Ten grams (10 g) of … Read more
Three forces, P, Q and R, of magnitudes 500 N, 200 N and 300 N respectively, act ona point O in the directions shown in the diagram below. The forces are NOT drawn to scale. 2.1 Refer to the information in the diagram above and give a reason why forcesP, Q and R are classified … Read more
Methane is used as an alternative fuel. The combustion of methane releases carbondioxide and water. The balanced equation for this reaction is:CH4(g) + O2 (g) → CO2 (g) + 2H2O (g) + 891 kJ.mol-1 The activation energy for this reaction is 172 kJ.mol-1. 7.1 Is this reaction ENDOTHERMIC or EXOTHERMIC? Give a reason for theanswer. … Read more
Learners made a mini volcano in a science laboratory by adding sodium bicarbonate toethanoic acid. They added 100 mâ„“ of a 0,2 mol. dm-3 ethanoic acid solution to 10 g of NaHCO3 to start the reaction of the volcano.The balanced equation for this reaction is: CH3COOH(aq) + NaHCO3(s) → CH3COONa(aq) + H2O(l) + CO2(g) 6.1 … Read more
5.1 Define the term concentration. (2) 5.2 Eight (8) grams of Na2S2O3 is dissolved in water to prepare 500 cm3 ofsolution. Calculate the concentration of the Na2S2O3 solution. (3) 5.3 A 10 g sample of a compound contains 2,66 g of potassium, 3,54 g ofchromium and 3,81 g of oxygen. 5.3.1 Define the term empirical … Read more
The reaction between dichromate ions (Cr2O7-2) and iron(II) ions (Fe2+) in an acidic medium is given below. 9.1 Determine the oxidation number of CHROMIUM in Cr2O7-2(aq).(2) 9.2 Define reduction in terms of electron transfer.(2) 9.3 Write down the FORMULA of the substance that undergoes oxidation. Explainthe answer in terms of oxidation numbers.(2) 9.4 Write down … Read more
3.1 As availability of water is becoming a major problem in South Africa, morepeople are intending to save water. Therefore some of them areinvestigating how they are billed and if the billing is correctly calculated. Mrs. Treace is one of those people and stays in Cape Town. She studied thewater tariffs for 2013–2014 carefully. Below … Read more
4.1 Charles’ Law describes the relationship between the volume and temperatureof an enclosed mass of gas at constant pressure. The volumes of a gas atdifferent temperatures at constant pressure are given in the table below. 4.1.1 Explain Charles’ Law in terms of the kinetic molecular theoryof gases. (2) 4.1.2 Draw a graph of volume versus … Read more
Learners conduct an experiment to investigate the effects of intermolecular forces onboiling points. They use 20 mâ„“ of each of the following compounds in theirinvestigation: water, sunflower oil, nail polish remover, glycerine and methylated spirits.The results are shown in the table below: 3.1 Define the term boiling point. (2) 3.2 Formulate an investigative question for … Read more
2.1.1 The total cost for Call package A is given by the following formula:Total cost (in Rand) = R100 + number of minutes more than 100 x R0,80 (a) Write down a formula which can be used to calculate thetotal cost in Rand for Call package B. (3) (b) If Call package B is used, … Read more