Some Basic Concepts of Chemistry: NEET questions with solutions

NEET uses this chapter for fast mole-concept arithmetic: counting particles, limiting reagents, empirical formulae and concentration conversions (molarity, molality, mole fraction). Marks are lost to unit slips (g vs kg, solution vs solvent mass), to skipping the limiting-reagent check, and to counting molecules when the question asks for atoms.

1. 1.How many hydrogen atoms are present in 5.1 g of ammonia (NH₃)?Mole concept and molar massesEasySingle correct
2. 2.A mass is recorded as 0.020300 g. How many significant figures does this reading contain?Uncertainty in measurement: significant figuresEasySingle correct
3. 3.5.4 g of aluminium is heated with 14.2 g of chlorine gas. The reaction is 2Al(s) + 3Cl₂(g) → 2AlCl₃(s). What is the maximum mass of AlCl₃…Limiting reagentMediumSingle correct
4. 4.12.0 g of urea (molar mass 60 g mol⁻¹) is dissolved in 200 g of water. The density of the resulting solution is 1.05 g mL⁻¹. What is the…Reactions in solutions: molarityMediumSingle correct
5. 5.An organic compound contains 54.5% carbon, 9.1% hydrogen and 36.4% oxygen by mass. Its vapour density (relative to hydrogen) is 44. What is…Empirical and molecular formulaMediumSingle correct
6. 6.Which observation is a direct illustration of the law of multiple proportions?Laws of chemical combinationsEasySingle correct
7. 7.Consider the following statements:Atomic and molecular massesMediumStatement based
8. 8.An aqueous solution of NaCl is 3.00 M and has a density of 1.25 g mL⁻¹. What is its molality?Reactions in solutions: molarity to molalityHardSingle correct
9. 9.25.0 g of a limestone sample that is 80% CaCO₃ by mass (the rest is unreactive) is treated with 200 mL of 1.5 M HCl.Stoichiometry with purity and limiting reagentHardSingle correct