All changes saved 30. Sodium metal is placed in a beaker of water. When the two substances make contact, sparks form and heat can be felt coming out of the reaction. This is due to the bonds of water breaking and a new substance known as sodium hydroxide being formed. Which of the following observations would indicate that this reaction is a chemical change? O The substances were in a beaker. Sodium metal is shiny. O Heat was formed. Water is a liquid.

Reaction of 2.0 L of hydrogen gas with 1.0 L of oxygen gas yields 2.0 L of water vapor. All gases are at the same temperature and pressure. Show how these data support the idea that oxygen gas is a diatomic molecule. Must we consider hydrogen to be a diatomic molecule to explain these results?

These questions concern the work of J. J. Thomson. a. From Thomsons work, which particles do you think he would feel are most important for the formation of compounds (chemical changes), and why? b. Of the remaining two subatomic particles, which do you place second in importance for forming compounds, and why? c. Propose three models that explain Thomson's findings and evaluate them. To be complete you should include Thomsons findings

Scientists J. J. Thomson and William Thomson (Lord Kelvin) made numerous contributions to our understanding of the atom’s structure. Which subatomic particle did J. J. Thomson discover, and what did this lead him to postulate about the nature of the atom? William Thomson postulated what became known as the “plum pudding” model of the atom’s structure. What did this model suggest?

Each of the following statements is true, but Dalton might have had trouble explaining some of them with his atomic theory. Give explanations for the following statements. a. The space-filling models for ethyl alcohol and dimethyl These two compounds have the same composition by mass (52% carbon, 13% hydrogen, and 35% oxygen), yet the two have different melting points, boiling points, and solubilities in water. b. Burning wood leaves an ash that is only a small fraction of the mass of the original wood. c. Atoms can be broken down into smaller particles. d. One sample of lithium hydride is 87.4% lithium by mass, while another sample of lithium hydride is 74.9% lithium by mass. However, the two samples have the same chemical properties.

Both atomic elements and molecular elements exist. Are there such entities as atomic compounds and molecular compounds? If so, provide an example and microscopic drawing. If not, explain why not.

Reference Section 5-2 to find the atomic masses of 12C and 13C, the relative abundance of 12C and 13C in natural carbon, and the average mass (in u) of a carbon atom. If you had a sample of natural carbon containing exactly 10,000 atoms, determine the number of 12C and 13C atoms present. What would be the average mass (in u) and the total mass (in u) of the carbon atoms in this 10,000-atom sample? If you had a sample of natural carbon containing 6.0221 1023 atoms, determine the number of 12C and 13C atoms present What would be the average mass (in u) and the total mass (in u) of this 6.0221 1023 atom sample? Given that 1 g = 6.0221 1023 u, what is the total mass of I mole of natural carbon in units of grams?

Indium oxide contains 4.784 g of indium for every 1.000 g of oxygen. In 1869, when Mendeleev first presented his version of the periodic table, he proposed the formula In2O3 for indium oxide. Before that time it was thought that the formula was InO. What values for the atomic mass of indium are obtained using these two formulas? Assume that oxygen has an atomic mass of 16.00.

The CRC Handbook, a large reference book of chemical and physical data, lists two isotopes of rubidium (Z=37). The atomic mass of 72.15 of rubidium atoms is 84.9118u. Through a typographical oversight, the atomic mass of the second isotope is not printed. Calculate that atomic mass.

How many platinum atoms are in a pure platinum ring weighing 4.32 g?