Mean molar mass：平均摩尔质量

Mean molar mass：平均摩尔质量 Name Date Pd CP Chemistry – Unit 5 Worksheet 3 1. Element X has two natural isotopes. The isotope with a mass number of 6 has a relative abundance of 7.5%. The isotope with a mass number of 7 has a relative abundance of 92.5%. Determine the average molar mass for the element from these figures. What is the true identity and atomic number of element X? 2. The element copper is found to contain the naturally occurring isotopes 6365Cu and Cu. The relative abundances are 69.1% and 30.9% 2929 respectively. Calculate the average molar mass of copper. 2343. Uranium has three isotopes with the following percent abundances: U 92 235 238(0.0058%), U(0.71%), U (99.23%). What do you expect the 9292 molar mass of uranium to be in whole numbers? Why? 107 4. A sample of silver as it occurs in nature is 51.8% of isotope Agand 47 109.48.2% of isotope Ag What is the average molar mass of silver? 47 Modeling Chemistry 1 U5 cp ws 3 2010 5. Ninety-two percent of the atoms of an element have a mass of 28.0 amu, 5.0% of the atoms have a mass of 29.0 amu, and the remaining atoms have a mass of 30.0 amu. Calculate the average molar mass and identify the element. 6. .Boron exists in two stable isotopes, boron-10 and boron-11. The average molar mass of boron is 10.80 g/mole. Calculate the relative abundance of each isotope of boron. 7. Antimony (Sb) exists in two stable isotopes, Sb-121 and Sb-123. From the average molar mass found in the Periodic Table, determine the relative abundances of these two isotopes. 8. Iridium (Ir) exists in two stable isotopes, Ir-191 and Ir-193. From the average molar mass found in the Periodic Table, determine the relative abundances of these two isotopes. Modeling Chemistry 2 U5 cp ws 3 2010