All Free Everyday Science MCQs with Answers

451. What is the molecular weight of Ammonia (NH3) ________ ?

• A. 17.031 g/mol
• B. 18.031 g/mol
• C. 19.031 g/mol
• D. 27.033 g/mol

Explanation: Ammonia has one nitrogen atom and three hydrogen atoms, so its molar mass is about 14.01 + 3(1.008) = 17.03 g/mol. Therefore 17.031 g/mol is the matching value.

452. What is the molecular formula for Ammonia?

• A. NH
• B. NH2
• C. NH3
• D. NH4

Explanation: Ammonia consists of one nitrogen atom bonded with three hydrogen atoms, giving the molecular formula NH3. NH4 refers to the ammonium ion only when it carries a positive charge.

453. What is the Molecular Formula for Glucose _______ ?

• A. C4H10O6
• B. C5H11O6
• C. C6H12O6
• D. S6H12O6

Explanation: Glucose is a six-carbon sugar with twelve hydrogen atoms and six oxygen atoms, so its formula is C6H12O6. The other formulas have incorrect atom counts or elements.

454. Which of the following is a diverse group of hydrophobic molecules?

• A. Carbohydrates
• B. Lipids
• C. Proteins
• D. Nucleic acids

Explanation: Lipids are a chemically diverse group of mostly hydrophobic molecules, including fats, oils, waxes and steroids. Carbohydrates, proteins and nucleic acids are generally more polar and water-compatible.

455. What is the chemical formula for Sulfuric acid?

• A. C2H6O
• B. CaSO4
• C. C2H4O2
• D. H2SO4

Explanation: Sulfuric acid contains two hydrogen atoms, one sulfur atom and four oxygen atoms, giving H2SO4. CaSO4 is calcium sulfate, not an acid.

456. A mixture of sand and naphthalene can be separated by ________ ?

• A. Chromatography
• B. Fractional distillation
• C. Sublimation
• D. None of these

Explanation: Naphthalene sublimes directly from solid to vapour on heating, while sand does not, allowing sublimation to separate them. The naphthalene vapour can then be cooled and collected as a solid.

457. What is the chemical formula for Sodium carbonate _______ ?

• A. Na3CO2
• B. CNa2O3
• C. Na2CO3
• D. Na3CO3

Explanation: Sodium carbonate contains two sodium ions for each carbonate ion, so its formula is Na2CO3. The subscripts balance the carbonate ion's 2− charge with two Na+ ions.

458. A 'breath test' used by traffic police to check drunken driving uses ____?

• A. Turmeric on filter paper
• B. Silica gel coated with silver nitrate
• C. potassium permanganate-sulphuric acid
• D. Potassium dichromatic-sulphuric acid

Explanation: A breathalyser uses acidified potassium dichromate, which changes colour when ethanol in exhaled air is oxidised. The option says dichromatic, but it clearly intends potassium dichromate.

459. Brass gets discoloured in air because of the presence of which of the following gases in air ________ ?

• A. Carbon dioxide
• B. Oxygen
• C. Nitrogen
• D. Hydrogen sulphide

Explanation: Hydrogen sulphide reacts with the copper and zinc components of brass, producing dark sulphide compounds that discolour its surface. Oxygen and nitrogen are normal air components but are not the specific cause intended here.

460. Elements which have same number of protons but different number of neutrons are called as _________ ?

• A. Isotopes
• B. Isomers
• C. Allotropes
• D. Allomers

Explanation: Isotopes have the same atomic number, meaning the same number of protons, but different numbers of neutrons and therefore different mass numbers. Isomers have the same formula but different structures.