Chapter 2, Problem 2.13E

Two elements, R and Q, combine to form two binary compounds. In the first compound, 14.0 g of R combines with 3.00 g of Q. In the second compound, 7.00 g of R combines with 4.50 g of Q. Show that these data are in accord with the law of multiple proportions. If the formula of the second compound is RQ, what is the formula of the first compound?

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 Thomsons findings and evaluate them. To be complete you should include Thomsons findings.

A sample of metallic element X, weighing 4.315 g, combines with 0.4810 L of Cl2 gas (at normal pressure and 20.0C) to form the metal chloride with the formula XCl. If the density of Cl2 gas under these conditions is 2.948 g/L, what is the mass of the chlorine? The atomic weight of chlorine is 35.45 amu. What is the atomic weight of X? What is the identity of X?

2.90 Naturally occurring europium has an average atomic weight of 151.964 amu. If the only isotopes of europium present are 151Eu and 153Eu, describe how you would determine the relative abundance of the two isotopes. Include in your description any information that would need to be looked up.

Early tables of atomic weights (masses) were generated by measuring the mass of a substance that reacts with 1.00 g of oxygen. Given the following data and taking the atomic mass of hydrogen as 1.00, generate a table of relative atomic masses for oxygen, sodium, and magnesium. Element Mass That Combines with 1.00g Oxygen Assumed Formula Hydrogen 0.126 g HO Sodium 2.875 g NaO Magnesium 1.500 g MgO How do your values compare with those in the periodic table? How do you account for any differences?

2.74 The accompanying table provides the identity of the two naturally occurring isotopes for four elements and the atomic weights for those elements. (In each case, the two isotopes differ in mass number by two.) Which element has the mass spectrum shown? Explain your answer.

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 ether are shown below. These two compounds have die 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 Ls 74.9% lithium by mass. However, the two samples have the same chemical properties.

What evidence led to the conclusion that cathode rays had a negative charge?

See the definition for isobars in Question 15. Consider Cr-54, Fe-54, Fess, and Ni-S8. (a) Which of these are isobars? Which are isotopes? (b) What do Fe-S4 and Fe-58 have in common? (c) Which atoms have the same number of neutrons?