A catalyst that slows down a reaction is known as: MCQ with Answer and Explanation

Explanation:
Across a period, nuclear charge increases while electrons are added to the same shell, leading to stronger attraction, so atomic radius decreases and ionization energy generally increases (with some exceptions like N to O due to half-filled stability). Metallic character decreases, non-metallic character increases. Electron affinity becomes more negative (increases in magnitude). Exam note: Ionization energy trend: Increases across period, decreases down group.

Explanation:
CNG (methane) has a higher H/C ratio, so combustion produces less CO₂ per unit energy compared to petrol/diesel. It also burns completely without generating smoke or particulate matter, and contains no sulfur, thus no SO₂. It reduces NOx and unburned hydrocarbons. It is used in vehicles and is safer in spills because it is lighter than air and disperses quickly.

Explanation:
The carbon-fluorine bond is one of the strongest covalent bonds, making PTFE resistant to attack by chemicals and heat. The fluorine atoms also shield the carbon backbone.