Some Basic Concepts of Chemistry

Explanation

When the digit being dropped is exactly 5, the convention is to leave the preceding digit unchanged if it is even and raise it by one if it is odd. In 17.0145 the preceding digit is 4, which is even, so it stays: 17.014. In 21.0235 it is 3, which is odd, so it rises: 21.024.

Explanation

Butane is C₄H₁₀, molar mass 58 g mol⁻¹, so 116 g is 2 moles. Complete combustion gives 4 CO₂ per butane, so 8 moles of CO₂ are produced, and 8 × 44 = 352 g.

Explanation

Dalton’s theory was built to account for the mass laws, and it explains conservation of mass, constant proportions and multiple proportions directly from indivisible atoms combining in fixed whole-number ratios. Gay-Lussac’s law of combining gaseous volumes is about volumes rather than masses, and reconciling it required Avogadro’s hypothesis that equal volumes contain equal numbers of molecules — an idea Dalton rejected.