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Give concise explanations for each of the following - VCE - SSCE Chemistry - Question 6 - 2005 - Paper 1
Question 6
Give concise explanations for each of the following. a. Food chemists quote the energy content of food in kJ g⁻¹, rather than kJ mol⁻¹. b. Hydrogen gas is bubbled ... show full transcript
Worked Solution & Example Answer:Give concise explanations for each of the following - VCE - SSCE Chemistry - Question 6 - 2005 - Paper 1
Step 1
a. Food chemists quote the energy content of food in kJ g⁻¹, rather than kJ mol⁻¹.
Answer
Food chemists prefer to quote the energy content of food in kJ g⁻¹ because this unit provides a more practical and easily relatable measure of energy available per gram of food consumed. Since food is usually consumed in grams, using kJ g⁻¹ allows consumers to quickly assess the energy content without needing to convert the mass of food consumed into moles, which would complicate dietary calculations.
Step 2
b. Hydrogen gas is bubbled through a solution of 1.0 M Fe²⁺(aq) ions.
Answer
In theory, a redox reaction is expected to occur based on the electrochemical series where hydrogen can displace iron from its solution. However, in practice, the reaction does not occur at room temperature because the activation energy required for the reaction is too high, or the kinetics of the reaction do not favor progress at this temperature.
Step 3
c. The oxidation state of iron, in its compounds, is normally either +2 or +3, whereas that of calcium, in its compounds, is +2 only.
Answer
Iron is a transition metal and can exhibit multiple oxidation states due to its ability to lose different numbers of electrons from both the 3d and 4s orbitals. Calcium, however, is an alkaline earth metal and consistently has an oxidation state of +2, as it predominantly loses its two 4s electrons. This difference arises from their respective electronic configurations and their positions in the periodic table.