Answer each of the following questions. Note that none of them should require difficult calculations. a. How many molecules are present in 1 mole of pentane ( C5H12)? molecules b. How many moles of fluorine atoms are present in 8 moles of C2F6? moles c. What is the approximate mass (to the nearest gram) of 3 x 1023 helium atoms?

Answer each of the following questions. Note that none of them should require difficult calculations. a. How many molecules are present in 1 mole of pentane ( C5H12)? molecules b. How many moles of fluorine atoms are present in 8 moles of C2F6? moles c. What is the approximate mass (to the nearest gram) of 3 x 1023 helium atoms?

Chemistry for Engineering Students

3rd Edition

ISBN:9781285199023

Author:Lawrence S. Brown, Tom Holme

Publisher:Lawrence S. Brown, Tom Holme

Chapter3: Molecules, Moles, And Chemical Equations

Section: Chapter Questions

Problem 3.85PAE

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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?
hat is the difference between the empirical and molecular for mulas of a compound? Can they ever be the same? Explain.
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.)
Calculate the mass in grams of each of the following samples. l type="a"> 0.994 mole of benzene, C6H6 i>4.21 moles of calcium hydride 1.79104 moles of hydrogen peroxide, H2O2 i>1.22 rnmol of glucose, C6H12O6(1mmol=11000mole) i>10.6 moles of tin 0.000301 moIe of strontium fluoride
. How many atoms of carbon are present in 1 .0 g of CH4O ? How many atoms of carbon are present in 1.0 of CH3CH2OH ? How many atoms of nitrogen are present in 25.0 g of CO( NH2)2 ?
Calculate the number of atoms of each element present in each of the following samples. l type='a'> 4.2 1 g of water 6.81 g of carbon dioxide 0.000221 g of benzene, C6H6 i>2.26 moles of C12H22O11
Calculate the percent by mass of the element listed first in the formulas for each of the following compounds. methane, CH4 sodium nitrate, NaNO3 carbon monoxide, CO nitrogen dioxide, NO2 1-octanol, C8H18O calcium phosphate, Ca3( PO4)2 3-phenyiphenol, C12H10O aluminum acetate, Al(C2H3O2)3
itamin B12 , cyancobalamin, is essential for human nutrition. Its molecular formula is C63H88CoN14O14P . A lack of this vita min in the diet can lead to anemia. Cyanocohalamin is the form of the vitamin found in vitamin supplements. l type='a'> What is the molar mass of cyanocobalamin to two decimal places? How many moles of cyanocohalamin molecules are present in 250 mg of cyanocobalamin? What is the mass of 0.60 mole of cyanocobalamin? How many atoms of hydrogen are in 1 .0 mole of cyanocobalamin? What is the mass of 1.0107 molecules of cyanocobalamin? What is the mass (in grams) of one molecule of cyanocobalamin?
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?
3.78 Consider two samples of liquid: I mole of water (H2O) and 1 mole of ethanol. Answer each of the following questions. Note that none of these should require significant calculations. (a) Which sample contains more atoms? (b) Which sample contains more molecules? (c) Which sample has a larger mass?
One chocolate chip used in making chocolate chip cookies has a mass of 0.324 g. (a) How many chocolate chips are there in one mole of chocolate chips? (b) If a cookie needs IS chocolate chips, how many cookies can one make with a billionth (1109) of a mole of chocolate chips? (A billionth of a mole is scientifically known as a nanomole.)
A binary compound of magnesium and nitrogen is analyzed, and 1.2791 g of the compound ¡s found to contain 0.9240 g of magnesium. When a second sample of this compound is treated with water and heated, the nitrogen is driven off as ammonia, leaving a compound that contains 60.31% magnesium and 39.69% oxygen by mass. Calculate the empirical formulas of the two magnesium compounds.