Free Chemistry in Daily Life MCQs with Answers

191. Which has the lowest pH?

• A. Hepatic Bile
• B. Gastric Juice
• C. Saliva
• D. Pancreatic Juice

Explanation: Gastric juice contains hydrochloric acid and normally has a pH of about 1 to 3, making it the most acidic option. Bile, saliva and pancreatic juice are generally alkaline or near neutral.

192. Which law states that the rate of the effusion of a gas is inversely proportional to the square root of its density?

• A. Graham's Law
• B. Gay-Lussac's law
• C. Boyle's law
• D. None of these

Explanation: Graham’s law states that the rate of effusion of a gas is inversely proportional to the square root of its density. Thus, lighter gases escape through a small opening faster than heavier gases.

193. Which law states that the volume of a given amount of gas held at constant pressure is directly proportional to the Kelvin temperature?

• A. Charles' Law
• B. Avogadro's Law
• C. Graham's Law
• D. Boyle's law

Explanation: Charles’ law links volume and absolute temperature at constant pressure: heating a gas increases its volume in direct proportion to its Kelvin temperature. Temperature must be expressed in Kelvin, not Celsius.

194. Which law states that "equal volumes of all gases, at the same temperature and pressure, have the same number of molecules?

• A. Boyle's law
• B. Charles' law
• C. Gay-Lussac's law
• D. Avogadro's law

Explanation: Avogadro’s law states that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules. This is why gas volume can be related directly to the amount of gas under fixed conditions.

195. Which gas is used to extinguish fire?

• A. Nitrous Oxide
• B. Methane
• C. Carbon Dioxide
• D. Carbon Dioxide & Nitrous Oxide

Explanation: Carbon dioxide helps extinguish fire by displacing oxygen around the flames and does not support combustion. It is therefore used in fire extinguishers, especially for electrical and flammable-liquid fires.

196. __________ gas is released when coal is burnes in ln lack of Oxygen?

• A. Carbon Dioxide
• B. Methane
• C. Ethene
• D. Carbon Monoxide

Explanation: Burning coal with insufficient oxygen causes incomplete combustion, producing carbon monoxide rather than the maximum possible carbon dioxide. Carbon monoxide is poisonous because it interferes with oxygen transport in blood.

197. Which of the following acid is used in Ink?

• A. Valeric
• B. Acetic
• C. Formic
• D. Tannic

Explanation: Tannic acid is used in traditional ink formulations, especially iron-gall ink, where it reacts with iron salts to produce a dark pigment. Acetic, formic, and valeric acids have different household and industrial uses.

198. How is ammonia synthesized?

• A. Herber process
• B. Regrigration process
• C. Contact process
• D. All of these

Explanation: Ammonia is manufactured by the Haber, or Haber-Bosch, process, which combines nitrogen and hydrogen under high pressure with an iron catalyst. The Contact process makes sulphuric acid, not ammonia.

199. Which is the purest form of water?

• A. Rain water
• B. Heavy water
• C. Tap water
• D. None of these

Explanation: Rainwater is generally regarded as the purest naturally occurring water among these choices because it forms through condensation and has not yet passed through soil or pipelines. It can still collect dust and gases while falling, so distilled water would be purer if it were listed.

200. Mohs' Scale" is used to indicate the_________?

• A. Degree of hardness of minerals
• B. Degree of viscosity of a liquid
• C. Degree of elasticity of a material
• D. Degree of brittleness of a substance

Explanation: The Mohs scale ranks minerals by their resistance to scratching, from talc at 1 to diamond at 10. It measures hardness, not viscosity, elasticity, or brittleness.