Since the penny was minted in 1969, only 95.00% by mass of the penny is copper. If the had a mass of 3.110 g, what is the mass of copper in the metal? penny How many moles of copper metal are in the penny? How many atoms of copper are in this many moles of copper?

What is the total mass (amu) of carbon in each of the following molecules? CH4 CHCl3 C12H12O6 CH3CH2CH2CH2CH3

You find a compound composed only of element X and chlorine, and you know that it is 13.102% element X by mass. Each molecule has 6 times as many chlorine atoms as X atoms. What is element X?

With the advent of techniques such as scanning tunneling microscopy, it is now possible to write with individual atoms by manipulating and arranging atoms on an atomic surface. a. If an image is prepared by manipulating iron atoms and their total mass is 1.05 1020 g, what number of iron atoms were used? b. If the image is prepared on a platinum surface that is exactly 20 platinum atoms high and 14 platinum atoms wide, what is the mass (grams) of the atomic surface? c. If the atomic surface were changed to ruthenium atoms and the same surface mass as determined in part b is used, what number of ruthenium atoms is needed to construct the surface?

By x-ray diffraction it is possible to determine the geometric pattern in which atoms are arranged in a crystal and the distances between atoms. In a crystal of silver, four atoms effectively occupy the volume of a cube 0.409 nm on an edge. Taking the density of silver to be 10.5 g/cm3, calculate the number of atoms in one mole of silver.

If one can find the ratio of the number of moles of the elements in a compound to one another, one can find the formula of the compound. In a certain compound of copper and oxygen, CuxOy, we find that a sample weighing 0.9573g contains 0.7649gCu. a. How many moles of Cu are there in the sample? (MolesofCu=massofCumolarmassofCu) _moles b. How many gram of O are there in the sample? The mass of the sample equals the mass of the Cu plus the mass of O. _g c. How many moles of O are there in the sample. _moles d. What is the mole ratio (molesofCu/molesofO) in the sample? _:1 e. What is the formula of the oxide? The atom ratio equals the mole ratio and is expressed using the smallest integers possible. _ f. What is the molar mass of the copper oxide? _g/mol

A jar contains some number of jelly beans. To find out precisely how many are in the jar, you could dump them out and count them. How could you estimate their number without counting each one? (Chemists need to do just this kind of bean counting when they work with atoms and molecules. Atoms and molecules are too small to count one by one, so chemists have worked out other methods to determine the number of atoms in a sample.)

Atomic masses are relative masses. What does this mean?

f an average sodium atom weighs 22.99 amu, how many sodium atoms are contained in 1.981013 amu of sodium? What will 3.011023 sodium atoms weigh?

erhaps the most important concept in introductory chemistry concerns what a mole of a substance represents. The mole concept will come up again and again in later chapters in this book. What does one mole of a substance represent on a microscopic, atomic basis? What does one mole of a substance represent on a macroscopic, mass basis? Why have chemists defined the mole in this manner?