Question 10

Gold and iron are two of many minerals mined in South Africa. Iron is mined inopen-cast mines, while gold is usually found in deep-shaft (underground) mines.During the process of refining, the following chemical reactions take place to extractthe metal from the ore: Gold is dissolved in a solution containing cyanide ions (CN–) to extract it … Read more

Question 9

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

Question 7

The equation for the combustion of butane gas is given below. 7.1 Define the term activation energy.(2) 7.2 Is the combustion reaction of butane exothermic or endothermic? Give areason for the answer.(2) 7.3 Draw a sketch graph of potential energy versus course of reaction for thereaction above. Clearly indicate the following on the graph: Activation … Read more

Question 4

In an experiment to investigate the relationship between pressure and temperature ofan enclosed gas, 48 g of oxygen gas was sealed in a container. The results obtainedare recorded in the table below. 4.1 Draw a graph of pressure versus temperature on the attached ANSWERSHEET. Extrapolate the graph so that it intersects the y-axis. (4) 4.2 … Read more

Question 3

Consider the list of six substances with their formulae and boiling points in the tablebelow. 3.1 Explain why ethanol is soluble in water. Refer to the relative strength of theintermolecular forces in ethanol and water. (3) 3.2 Explain why the boiling point of iodine is higher than that of bromine. Refer tothe intermolecular forces present … Read more