Postulate of Dalton’s Theory: Consistent with the Law of Conservation of Mass.
Observation: Heating 100 grams of solid calcium carbonate produces 44 grams of carbon dioxide and 56 grams of calcium oxide.
Explanation: Total mass of reactants (100 g) equals total mass of products (44 g + 56 g = 100 g).
Postulate Violated: Dalton's postulate states that all atoms of a given element are identical in mass and properties.
Observation: Two samples of titanium dioxide show different percentages of titanium (59.95% and 60.10%).
Explanation: This variation implies that the titanium in those samples has different isotopic compositions or mixtures, thus violating the postulate.
Observation: Iron nail corroding forms rust (Iron (III) oxide).
(a) Expectation for Mass Change: Mass increases after rust formation.
Explanation: Iron combines with oxygen, gaining mass from the added oxygen.
(b) Mass Calculation:
Final mass = 24.1 g, initial mass = 23.2 g.
Mass gained = 24.1 g - 23.2 g = 0.9 g (mass of oxygen combined).
Fermentation process: Yeast converts glucose to ethanol and carbon dioxide.
(a) Total Mass of Products: If 200.0 g of glucose is fully converted, the mass of ethanol and carbon dioxide remains 200.0 g.
(b) Expectation for Mass Change in Open Container: Mass would be less after fermentation.
Explanation: CO2 escapes into the atmosphere, reducing total mass.
(c) Mass of Ethanol Calculation:
If 97.7 g of CO2 is produced, the mass of ethanol = 200.0 g - 97.7 g = 102.3 g.
Ion Symbol Writing:
(a) Ion with 1+ charge, atomic number 55, mass number 133: Cs⁺ (Cesium)
(b) Ion with 54 electrons, 53 protons, 74 neutrons: I⁻ (Iodine)
(c) Ion with atomic number 15, mass number 31, 3− charge: P³⁻ (Phosphide)
(d) Ion with 24 electrons, 30 neutrons, 3+ charge: Cr³⁺ (Chromium)
Protons, Electrons, Neutrons in Isotopes:
(a) Boron-10: 5 protons, 5 electrons, 5 neutrons.
(b) Mercury-199: 80 protons, 80 electrons, 119 neutrons.
(c) Copper-63: 29 protons, 29 electrons, 34 neutrons.
(d) Carbon-13: 6 protons, 6 electrons, 7 neutrons.
(e) Selenium-77: 34 protons, 34 electrons, 43 neutrons.
Element's Natural Abundances and Isotopic Masses:
Abundances/Isotopic masses:
90.92% at 19.99 amu
0.26% at 20.99 amu
8.82% at 21.99 amu
Average atomic mass calculation = (0.9092 * 19.99) + (0.0026 * 20.99) + (0.0882 * 21.99)
Average Atomic Mass of Bromine:
Isotopes: 79Br (mass: 78.9183, abundance: 50.69%) and 81Br (mass: 80.9163, abundance: 49.31%).
Calculation:
Average atomic mass = (0.5069 * 78.9183) + (0.4931 * 80.9163)
Average Atomic Mass of Lithium Sources:
Natural Composition: 7.5% for 6Li (6.01512 amu) and 92.5% for 7Li (7.01600 amu).
Commercial Source: 3.75% for 6Li (with the rest as 7Li).
Calculations for both sources regarding average atomic mass.
Variations in Average Atomic Mass of Boron:
Isotopes: 10B (10.0129 amu) and 11B (11.0931 amu).
Percent Abundance Calculations:
Calculate abundances leading to average atomic masses of 10.807 and 10.819.
Oxygen Isotopes in Meteorites:
Observation: 18O:16O abundance ratio is greater in meteorites than on Earth.
Conclusion: Average mass of oxygen atoms in meteorites is greater than that of terrestrial oxygen atoms.