One mole (mol) of ethanol (C2H8O) has a mass of 46.0684 g.  a. How many molecules of ethanol are in 2.1 mol of ethanol? (you will need to use Avogadro's number!) b. How many moles of ethanol are in an 18.0 g sample? c. What is the mass (in kg) of 2.1 mol of ethanol?

Moles within Moles and Molar Mass Part 1: a How many hydrogen and oxygen atoms are present in 1 molecule of H2O? b How many moles of hydrogen and oxygen atoms are present in 1 mol H2O? c What are the masses of hydrogen and oxygen in 1.0 mol H2O? d What is the mass of 1.0 mol H2O? Part 2: Two hypothetical ionic compounds are discovered with the chemical formulas XCl2 and YCl2, where X and Y represent symbols of the imaginary elements. Chemical analysis of the two compounds reveals that 0.25 mol XCl2 has a mass of 100.0 g and 0.50 mol YCl2 has a mass of 125.0 g. a What are the molar masses of XCl2 and YCl2? b If you had 1.0-mol samples of XCl2 and YCl2, how would the number of chloride ions compare? c If you had 1.0-mol samples of XCl2 and YCl2, how would the masses of elements X and Y compare? d What is the mass of chloride ions present in 1.0 mol XCl2 and 1.0 mol YCl2? e What are the molar masses of elements X and Y? f How many moles of X ions and chloride ions would be present in a 200.0-g sample of XCl2? g How many grams of Y ions would be present in a 250.0-g sample of YCl2? h What would be the molar mass of the compound YBr3? Part 3: A minute sample of AlCl3 is analyzed for chlorine. The analysis reveals that there are 12 chloride ions present in the sample. How many aluminum ions must be present in the sample? a What is the total mass of AlCl3 in this sample? b How many moles of AlCl2 are in this sample?

3.79 Consider two samples. Sample A contains 2 moles of N2 and 1 mole of O2, and Sample B contains 1 mole of N2O5. (a) Which sample contains more molecules? (b) Which sample contains more oxygen atoms? (c) Which sample contains more nitrogen atoms?

High-density lipoprotein (HDL) cholesterol is the good cholesterol because adequate levels reduce the risk of heart disease and stroke. HDL levels between 40. and 59 mg/dL are typical for a healthy individual. What is this range of HDL cholesterol in units of mol/L? The formula for cholesterol is C27H46O.

Consider the following diagram, where atom X is represented by a square and atom Y is represented by a circle. (a) Write the equation for the reaction represented by the diagram. (b) If each circle stands for a mole of Y and each square a mole of X, how many moles of X did one start with? How many moles of Y? (c) Using the same representation described in part (b), how many moles of product are formed? How many moles of X and Y are left unreacted?

An Alka-Seltzer tablet contains 324 mg of aspirin (C.9H8O4,), 1904 mg of NaHCO3, and 1000. mg of citric add (H3C6H5O7). (The last two compounds react with each other to provide the "fizz," bubbles of CO2, when the tablet is put into water.) (a) Calculate the amount (moles) of each substance in the tablet. (b) If you take one tablet, how many molecules of aspirin are you consuming?

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?

Considering your answer to Exercise 79, which type of formula, empirical or molecular, can be obtained from elemental analysis that gives percent composition?

Suppose that the atomic mass of C-12 is taken to be 5.000 amu and that a mole is defined as the number of atoms in 5.000 kg of carbon-12. How many atoms would there be in one mole under these conditions? (Hint: There are 6.0221023 C atoms in 12.00 g of C-12.)

Uranium is used as a fuel, primarily in the form of uranium(IV) oxide, in nuclear power plants. This question considers some uranium chemistry. A small sample of uranium metal (0.169 g) is heated to 900 °C in air to give 0.199 g of a dark green oxide, UxOy. How many moles of uranium metal were used? What is the empirical formula of the oxide UxOy? What is the name of the oxide? How many moles of UxOy, must have been obtained? The oxide UxOy is obtained if UO2NO3 · n H2O is heated to temperatures greater than 800 °C in air. However, if you heat it gently, only the water of hydration is lost. If you have 0.865 g UO2NO3 · n H2O and obtain 0.679 g UO2NO3 on heating, how many molecules of water of hydration were there in each formula unit of the original compound?