CDS Basic Concepts of Chemistry

According to the modern atomic theory, atoms of the same element must have the same number of:

What is the empirical formula of a compound containing 40% carbon, 6.67% hydrogen, and 53.33% oxygen by mass?

What is the SI unit of amount of substance?

How many significant figures are present in the measurement 0.00450 kg?

If 2.0 moles of oxygen gas (O₂) react completely with hydrogen to form water, how many moles of water are produced? (2H₂ + O₂ → 2H₂O)

When 2.4 g of carbon completely burns in oxygen, how many moles of CO₂ are produced? (Atomic mass: C = 12, O = 16)

If 5 moles of H₂ react with 2.5 moles of O₂ according to 2H₂ + O₂ → 2H₂O, which reactant is limiting?

Which of the following statements best defines the mole concept in chemistry?

What is the empirical formula of a compound that contains 40% carbon, 6.67% hydrogen, and 53.33% oxygen by mass?

Which of the following represents the correct relationship between molarity and molality for a dilute aqueous solution?

What is the oxidation state of sulfur in the compound H₂SO₄?

A solution has a pH of 3. What is its hydrogen ion concentration [H⁺] in mol/L?

Which law states that the total pressure of a mixture of gases is equal to the sum of partial pressures of individual gases?

A sample contains 3.011 × 10²³ atoms of carbon. Calculate the mass of carbon in grams. (Atomic mass of C = 12 u, Avogadro's number = 6.022 × 10²³)

Which of the following correctly represents the relationship between molarity (M), molality (m), and density (d) for a solution?

An element has an electron configuration of [Ar] 3d⁵ 4s². Its position in the periodic table and the number of unpaired electrons in the ground state are: