Question 1

Which of the following is the main component of natural gas used for cooking and heating in households?

Accepted Answer

Methane (CH₄) is the primary component of natural gas, typically comprising 70–90% of the gas mixture. It is a simple hydrocarbon that burns cleanly to produce heat and is the most abundant component in commercial natural gas supplied to homes.

Question 2

Which of the following is the chemical formula for common salt used in kitchens?

Accepted Answer

Common salt, also known as table salt or sodium chloride, has the chemical formula NaCl. It consists of one sodium atom and one chlorine atom bonded together.

Question 3

Which of the following is an example of a physical change?

Accepted Answer

A physical change is a change in the physical properties of a substance without altering its chemical composition. Melting of ice is a physical change because ice and water are the same substance (H₂O) in different physical states.

Question 4

What is the pH value of pure distilled water at 25°C?

Accepted Answer

Pure distilled water at 25°C has a pH of 7, which is considered neutral. At this pH, the concentration of hydrogen ions (H⁺) equals the concentration of hydroxide ions (OH⁻).

Question 5

Which gas is released when an acid reacts with a carbonate or bicarbonate?

Accepted Answer

When an acid reacts with a carbonate (e.g., CaCO₃) or bicarbonate (e.g., NaHCO₃), carbon dioxide (CO₂) gas is released along with water and a salt. This is a characteristic reaction of carbonates and bicarbonates.

Question 6

What is the main component of natural gas used for cooking and heating in homes?

Accepted Answer

Methane (CH₄) is the primary component of natural gas, typically comprising 70–90% of the gas mixture. It is a hydrocarbon and is the simplest alkane.

Question 7

Which of the following statements correctly explains why salt (sodium chloride) dissolves in water but not in kerosene oil?

Accepted Answer

Salt (NaCl) is an ionic compound that dissolves in polar solvents like water but not in non-polar solvents like kerosene. Water's polar molecules can surround and separate Na⁺ and Cl⁻ ions through ion-dipole interactions, while kerosene's non-polar molecules cannot.

Question 8

Milk of magnesia, commonly used as an antacid, contains magnesium hydroxide [Mg(OH)₂]. Why is it effective in treating acidity in the stomach?

Accepted Answer

Magnesium hydroxide is a weak base that neutralizes excess hydrochloric acid (HCl) in the stomach through an acid-base reaction: Mg(OH)₂ + 2HCl → MgCl₂ + 2H₂O. This reduces stomach acidity and provides relief from heartburn and indigestion.

Question 9

When iron filings are exposed to air and moisture, they rust. Which of the following best describes the chemical process occurring during rusting?

Accepted Answer

Rusting is an oxidation reaction where iron (Fe) reacts with oxygen (O₂) and water (H₂O) to form hydrated iron(III) oxide (Fe₂O₃·xH₂O). This is a redox reaction where iron is oxidized and oxygen is reduced, requiring both oxygen and moisture to occur.

Question 10

Which of the following is the primary reason why water is called a universal solvent in everyday chemistry?

Accepted Answer

Water dissolves more substances than any other liquid because of its polar nature. The bent molecular structure of H₂O creates a partial positive charge on hydrogen atoms and partial negative charge on oxygen, allowing it to dissolve both ionic compounds and polar molecules effectively.

Question 11

In everyday life, baking soda (sodium bicarbonate) reacts with vinegar (acetic acid) to produce carbon dioxide gas. Which of the following correctly identifies all the products of this reaction?

Accepted Answer

The reaction between sodium bicarbonate (NaHCO₃) and acetic acid (CH₃COOH) is: NaHCO₃ + CH₃COOH → CH₃COONa + H₂O + CO₂. The three products are sodium acetate, water, and carbon dioxide gas (the gas that causes fizzing).

Question 12

Which of the following correctly describes the difference between a mixture and a compound?

Accepted Answer

Mixtures and compounds are fundamentally different in their composition, properties, and how they are formed. This is a foundational chemistry concept.

Question 13

In chemistry, the pH of a solution is defined as the negative logarithm (base 10) of hydrogen ion concentration. At 25°C, a solution with a hydrogen ion concentration of 10⁻⁵ mol/L would have a pH of approximately:

Accepted Answer

pH = -log[H⁺]. When [H⁺] = 10⁻⁵ mol/L, pH = -log(10⁻⁵) = -(-5) = 5. This is an acidic solution (pH < 7). The question tests understanding of logarithmic pH scale and its practical application in identifying solution acidity.

Question 14

Which of the following statements about hard water is CORRECT?

Accepted Answer

Hard water contains dissolved minerals, primarily calcium and magnesium salts. Understanding its properties and effects is important for everyday chemistry.

SSC MTS Chemistry — Everyday Concepts

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