Chapter 12

 

Completion

Complete each sentence or statement.

 

                  1.      The mass in atomic mass units of one molecule of a compound is the _______________ of the compound.

 

                  2.      The volume occupied by one mole of a gas at standard temperature and pressure is the _______________ of the gas.

 

                  3.      The ___________________ of a compound expresses the smallest whole number ratio of the atoms in the compound.

 

                  4.      A unit of measure used to count the number of atoms, molecules, or formula units of a substance is the _______________.

 

                  5.      The relationship among the pressure, volume, temperature, and number of particles in a gas is the _______________.

 

                  6.      The mass in atomic mass units of one formula unit of a compound is the _______________ of the compound.

 

                  7.      The number of items contained in one mole of any substance is called the ____________________.

 

                  8.      The mass of one mole of an element or compound is its _______________.

 

                  9.      The study of relationships between measurable quantities, such as mass and volume, and the number of atoms in chemical reactions is known as _______________.

 

                  10.      The formula NaCl is an example of a(n) _______________.

 

                  11.      There are 6.02 x 10²³ paper clips in a _______________ of paper clips.

 

                  12.      The numerical value of the ____________________ is 6.02 x 10²³.

 

                  13.      The amount of product of a chemical reaction can be predicted by _______________.

 

                  14.      The compounds CH₂O and C₆H₁₂O₆ have the same _______________.

 

Matching

 

Match each item with the correct item below.

a.	formula mass
b.	ideal gas law
c.	study that relates mass to number of particles
d.	percent yield
e.	one molecule or one mole
f.	6.02 x 1023
g.	0.10 mole
h.	molar mass
i.	molar volume
j.	0.25 mole
k.	8.31 kPa ·L/mol ·K
l.	atomic mass unit
m.	empirical formula

 

 

____          15.      Avogadro constant

 

____          16.      CO₂

 

____          17.      R

 

____          18.      2 g of H₂

 

____          19.      u

 

____          20.      58.5 u of NaCl

 

____          21.      NaCl

 

____          22.      22.4 L

 

____          23.      PV = nRT

 

____          24.      ratio of mass of product obtained to mass expected

 

____          25.      stoichiometry

 

____          26.      24.5 g of H₂SO₄

 

____          27.      2.24 L of a gas at STP

 

Short Answer

 

                  28.      What information do you need to determine the chemical formula of an unknown compound?

 

                  29.      Why is it inaccurate to say "CO is 50 percent oxygen"?

 

                  30.      When 0.500 mole of sodium is produced according to the reaction 2NaN₃(s) ® 3N₂(g) + 2Na(s), how many moles of nitrogen gas are also produced?

 

                  31.      A bottle contains 6.23 g of copper turnings. The mass of a length of magnesium ribbon is 6.23 g. Are there more copper atoms or more magnesium atoms present?

 

                  32.      A balloon is filled with helium gas. Another balloon, of the same size, is filled with nitrogen gas. Explain why the ratio of the masses of the two samples is the same as the ratio of their molar masses.

 

                  33.      Carbon dioxide gas and hydrogen gas react to form methanol gas. Assuming the process is 100 percent efficient, how many liters of each reactant are needed to obtain 0.500 L of methanol? The reaction is CO₂(g) + 3H₂(g) ® CH₃OH(g) + H₂O(g).

 

                  34.      How many chlorine molecules are in 35.5 g of chlorine gas?

 

                  35.      How many atoms are there in 106.2 g of potassium?

 

                  36.      What is the molar mass of ammonium sulfate?

 

                  37.      What is the number of moles represented by 38.1 g of FeCl₃?

 

                  38.      What is the mass in grams of 0.30 mol of NaHCO₃?

 

                  39.      Calcium oxide can be prepared by heating calcium metal in oxygen according to the reaction: 2Ca + O₂ ® 2CaO. How much calcium would be needed to make 15.0 g of calcium oxide?

 

                  40.      Hydrogen gas reacts with copper(II) oxide to form copper metal and water vapor according to the reaction: CuO + H₂ ® Cu + H₂O. What mass of copper is produced if 255 L of hydrogen at STP are used up in this reaction?

 

A chemical plant is being designed to manufacture ethanol (ethyl alcohol; C₂H₅OH) by treating ethylene (ethene; C₂H₄) gas with water, using phosphoric acid as a catalyst. Answer the following questions about this process.

 

                  41.      Write the chemical equation that represents the reaction by which ethanol is formed.

 

                  42.      Suppose that ethylene is to be supplied to the reaction chamber at the rate of 100.0 L per minute at 300.0ºC and 7.00 x 10³ kPa. At what rate in moles per minute is ethylene being supplied to the reaction chamber?

 

                  43.      What is the anticipated rate in grams per minute at which ethanol will be formed under the conditions described above?

 

                  44.      In the first pass of ethene through the reaction chamber, the actual rate of production of ethanol is 271 g/min. What is the percent yield for the reaction?

 

                  45.      If the unused ethene is passed through the reaction chamber again, 12.8 moles of ethanol are produced, compared to a theoretical yield of 13.2 moles. What is the percent yield?

 

                  46.      What are the molar masses of the following substances: osmium, fluorine, cobalt(II) nitrate, and nitrogen trichloride?

 

                  47.      Determine the number of atoms in each sample: 62.1 g titanium, Ti; 9.24 g neon, Ne; and 879 g lead, Pb.

 

                  48.      Without calculating, decide whether 15.0 g of magnesium or 15.0 g of manganese represents the greater number of atoms. Verify your answer by calculating.

 

                  49.      Determine the number of moles in each sample: 362 g strontium iodide, SrI₂; 4.85 g phenol, C₆H₅OH; and 61.0 g aluminum thiocyanate, Al(CNS)₃.

 

                  50.      Determine the mass of these molar quantities: 4.52 mol chlorine dioxide, ClO₂; 0.687 mol benzylamine, C₇H₉N; and 0.281 mol barium bromate, Ba(BrO₃)₂.

 

                  51.      Determine the number of units in this sample. Identify the unit as a formula unit or a molecule. 58.0 g chromium(III) sulfate, Cr₂(SO₄)₃

 

                  52.      Hydrocortisone acetate, C₂₃H₃₂O₆, is used to treat skin irritations. What is the molecular mass of hydrocortisone acetate? What is its molar mass?

 

                  53.      What mass of uranium contains the same number of atoms as 12.7 g of lithium?

 

                  54.      Calculate the mass of precipitate that forms when 300 mL of an aqueous solution containing 67.0 g of silver nitrate reacts with excess sodium chloride solution by the following reaction:

AgNO₃(aq) + NaCl(aq) ® NaNO₃(aq) + AgCl(s).

 

                  55.      What volume of hydrogen gas can be produced by reacting 3.86 g of aluminum in excess hydrochloric acid at 21.0ºC and 102 kPa? The reaction is 2Al(s) + 6HCl(aq) ® 2AlCl₃(aq) + 3H₂(g).

 

                  56.      How many moles of helium are contained in a 5.60-L cylinder at 720 kPa and 22.0ºC?

 

                  57.      What is the volume of 0.625 mol of nitrogen at 74.2 kPa and 85ºC?

 

                  58.      Toluene, C₇H₈, is one of the components of gasoline. Write the balanced chemical equation for the combustion of toluene to form carbon dioxide gas and water vapor. If 5.00 moles of toluene burn, how many moles of oxygen are consumed? How many moles of carbon dioxide are produced? How many grams of water vapor are produced?

 

                  59.      When a solution of 15.0 g of lead(II) nitrate in 100 g of water is mixed with a solution of 12.5 g of potassium iodide in 100 g of water, a double displacement reaction occurs. The balanced chemical equation is shown below. Which is the limiting reactant? How many grams of precipitate will form?

 

Pb(NO₃)₂(aq) + 2KI(aq) ® 2KNO₃(aq) + PbI₂(s)

 

                  60.      What is the molecular formula of each of the following compounds: a) empirical formula: C₄H₃O; molar mass: 268 g/mol, b) empirical formula: C₃H₅O₄; molar mass: 210 g/mol, c) empirical formula: C₁₁H₁₁N₂O; molar mass: 374 g/mol?

 

                  61.      Without calculating, which of the following compounds has the greater percentage of oxygen: FePO₄ or Fe₃(PO₄)₂? How do you know?

 

                  62.      An oxide of manganese is 72.0 percent manganese by mass. The molar mass of the oxide is 229 g/mol. What is the formula of the compound?

 

                  63.      Determine the percent fluorine in the following fluoride of chromium.

 

chromium(II) fluoride, CrF₂

 

                  64.      Methylal is a compound that is used in perfumery. Methylal is 47.3 percent C, 10.6 percent H, and 42.1 percent O. The molar mass is approximately 76 g/mol. What is the molecular formula of methylal?

 

                  65.      A 5.40-g sample of sodium hydrogen carbonate reacts with excess acetic acid to form sodium acetate by the reaction below. When the reaction is complete, 4.80 g of sodium acetate are recovered. What is the percent yield?

 

NaHCO₃(s) + HC₂H₃O₂(aq) ® NaC₂H₃O₂(aq) + CO₂(g) + H₂O(l)

 

Problem

 

Nitrogen and oxygen combine with each other to form a series of compounds. This chart summarizes laboratory research done on this series of compounds. From the data supplied, calculate the empirical and molecular formulas for each oxide listed.

 

Compound	Percentage Nitrogen	Percentage Oxygen	Molecular  Mass
A	63.6	36.4	44.01 u
B	30.4	69.6	46.00 u
C	36.9	63.1	76.01 u
D	25.9	74.1	108.01 u
E	46.7	53.3	30.01 u

 

 

                  66.      Compound A is _______________.

 

                  67.      Compound B is _______________.

 

                  68.      Compound C is _______________.

 

                  69.      Compound D is _______________.

 

                  70.      Compound E is _______________.