Explanation

Number of neutrons = Mass number − Atomic number = 19 − 9 = 10

Atomic number (9) is the number of protons; mass number (19) is protons + neutrons.

Explanation

LPG (Liquefied Petroleum Gas) mainly consists of hydrocarbons like propane and butane.

These are gases composed of hydrogen and carbon atoms.

It is used as fuel for cooking and heating.

Explanation

Burning pure hydrogen produces only water vapor as a byproduct, causing no harmful pollution like carbon or sulfur oxides.

Hence, hydrogen is considered a clean fuel with no emission of pollutants such as sulphur dioxide or carbon dioxide.

Explanation

Helium (He) is a noble gas.

Its atoms do not naturally bond with each other under standard conditions.

It exists as monoatomic (single-atom) molecules.

Nitrogen (N₂), Oxygen (O₂), and Hydrogen (H₂) are diatomic molecules.

It means they naturally form bonds between two atoms of the same element.

Explanation

The atomic number of silver (Ag) is 47. Its electronic configuration is [Kr] 4d¹⁰ 5s¹.

The valence electrons are in the outermost shell, which is the 5s orbital with 1 electron.

The number of valence electrons is 1.

Explanation

Calcium carbonate (CaCO₃) is insoluble in water due to its strong ionic lattice and low solubility product.

In contrast, salts like sodium and potassium compounds are generally highly soluble in water.

Explanation

CaCO₃ → CaO + CO₂

This reaction absorbs heat to break calcium carbonate into calcium oxide and carbon dioxide.

It is a classic endothermic decomposition reaction, requiring continuous heating to proceed.

Explanation

2H₂ + O₂ → 2H₂O

This balanced equation ensures 4 hydrogen atoms and 2 oxygen atoms on both sides.

It correctly represents the formation of water from hydrogen and oxygen gases.

Explanation

Explanation

Skimmed milk has nearly all fat removed, making it ideal for producing non-fat yogurt.

This type of yogurt contains less than 0.5% fat, suitable for low-calorie or fat-free diets.