An atom has 18 electrons and 22 neutrons. Its mass number is: MCQ with Answer and Explanation

Explanation:
Petroleum (crude oil) is a complex mixture of hydrocarbons including alkanes, cycloalkanes, aromatics, and smaller amounts of other compounds containing sulfur, nitrogen, oxygen. It is separated into fractions by fractional distillation.

Explanation:
Ethane: H₃C-CH₃. There is one C-C single bond and six C-H single bonds, total 7 covalent bonds. Each bond is a sigma bond. The structural formula shows 7 bonds. Methane has 4, propane 10. Counting bonds is simple: each line represents a covalent bond.

Explanation:
Enzymes are proteinaceous substances that act as biological catalysts, speeding up biochemical reactions in living organisms without being consumed. They are highly specific and work under mild conditions (pH, temperature). Examples: amylase breaks down starch, pepsin digests proteins. Inorganic catalysts are like Pt, Ni. Lipids are fats, not catalysts. Negative catalysts (inhibitors) slow reactions. Enzymes may be deactivated by high temperature or extreme pH.