Calorific value is the amount of heat energy produced by complete combustion of unit mass of a fuel. SI unit is J/kg, often expressed as kJ/kg or MJ/kg. Previously, kcal/kg or cal/g was used. 1 cal = 4.184 J. Higher calorific value indicates better fuel. Example: hydrogen has very high calorific value ~150 MJ/kg. Exam note: Calorific value is measured by bomb calorimeter.
Explanation:
A catalyst lowers the activation energy barrier by providing a different reaction mechanism. This allows more reactant molecules to have sufficient energy to react. It does not change the thermodynamics (ΔH, equilibrium constant) or get consumed in the reaction. Enzymes are biological catalysts.
Explanation:
Fermentation of sugars (glucose, fructose) by yeast enzymes produces ethanol and carbon dioxide: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂. Starch is first hydrolysed to glucose. Proteins and fats are not directly fermented to ethanol.
Explanation:
Atomic radius increases down a group as the number of shells increases. Iodine (I) is in Period 5, below F (2), Cl (3), Br (4). Thus iodine has the largest atomic radius among these halogens.
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