Deck 12: Chemical Reactions

Question 1

The scientist whose experiments showed that tin, upon heating, combined with a gas from the air was

A) Priestley.
B) Stahl.
C) Lavoisier.
D) Becher.

Answer 1

Lavoisier.

Question 2

Plants cannot make use of atmospheric nitrogen to form proteins because the atoms in a nitrogen molecule are held together by

A) single bonds
B) double bonds
C) triple bonds
D) quadruple bonds

Answer 2

triple bonds

Question 3

The decomposition of an unstable compound usually

A) occurs only at low temperatures.
B) requires a catalyst to occur.
C) is endothermic.
D) is exothermic.

Answer 3

is exothermic.

Question 4

Reaction rates increase with temperature mainly because a rise in temperature increases

A) the number of ions.
B) the number of polar molecules.
C) the number of activated molecules.
D) the average length of time between molecular collision.

Question 5

At ordinary temperatures, the temperature increase needed to double the rate of many common chemical reactions is

A) 1°C.
B) 10°C.
C) 50°C.
D) 100°C.

Question 6

Chemical reactions that give off energy are called

A) endothermic.
B) exothermic.
C) activated.
D) oxidation-reduction.

Question 7

One mole of which of the following compounds contains the largest number of fluorine atoms?

A) HF
B) SF₂
C) BF₃
D) XeF₆

Question 8

Which of the following compounds is not classed as an oxide?

A) CO₂
B) SiO₂
C) BaSO₄
D) H₂O

Question 9

Whether a chemical reaction is endothermic or exothermic depends on

A) the bond energies of the reactants.
B) the bond energies of the products.
C) both of the above energies.
D) neither of the above energies.

Question 10

The proportion of oxygen in dry air is about

A) 1/5.
B) 1/3.
C) 1/2.
D) 4/5.

Question 11

An example of an exothermic process is the

A) dissociation of a salt in water solution.
B) neutralization of an acid by a base.
C) electrolysis of water.
D) melting of ice.

Question 12

The speed of a chemical reaction is not affected by

A) the surface area of the reactants.
B) catalysts.
C) the concentration of reactants.
D) the type of bond in reaction products.

Question 13

According to Aristotle, every flammable material consisted of

A) earth and fire.
B) phlogiston.
C) oxygen and earth.
D) air and heat.

Question 14

Which of the following statements about ozone is incorrect?

A) The formula of ozone is O₃.
B) Ozone molecules are more stable than those of ordinary oxygen.
C) At low altitudes ozone contributes to smog.
D) At high altitudes ozone absorbs solar ultraviolet radiation.

Question 15

When sodium and chlorine react to form sodium chloride NaCl), 411 kJ per mole of NaCl is given off. To break up 1 mole of NaCl into sodium and chlorine requires

A) less than 411 kJ.
B) 411 kJ.
C) more than 411 kJ.
D) any of the above, depending on the circumstances.

Question 16

When a metal is oxidized, the resulting oxide

A) has less mass than the original metal.
B) has the same mass as the original metal.
C) has more mass than the original metal.
D) Any of these choices could be correct, depending on the metal.

Question 17

The number of formula units in a mole of a substance

A) depends on the formula mass of the substance.
B) depends on whether the substance is an element or a compound.
C) depends on whether the substance is a gas, a liquid, or a solid.
D) is the same for all substances.

Question 18

If a certain reaction is endothermic, the reverse reaction

A) cannot occur.
B) may occur spontaneously.
C) cannot occur spontaneously.
D) absorbs energy.

Question 19

An oxide decomposed by heating will give

A) oxygen and another element.
B) CO₂ and water.
C) oxygen ions and metal ions.
D) a metal and water.

Question 20

An example of slow oxidation is

A) a lighted candle.
B) the rusting of iron.
C) the lighting of a match.
D) a log burning in a fireplace.

Question 21

The atomic mass of N is 14 u and that of Ca is 40 u. The proportion of N by mass in the compound Ca₃N₂ is

A) 19 percent.
B) 35 percent.
C) 40 percent.
D) 81 percent.

Question 22

When a substance loses electrons in a chemical reaction, the substance is said to be

A) reduced.
B) oxidized.
C) dissociated.
D) activated.

Question 23

Of the following battery types, the one with the highest energy density is

A) lead-acid.
B) lithium-ion.
C) nickel-cadmium.
D) nickel-metal-hydride.

Question 24

The time needed for a strong acid to neutralize a strong base in solution

A) decreases with temperature.
B) increases with temperature.
C) is virtually independent of temperature.
D) Any of these choices could be correct, depending on the particular acid and base.

Question 25

Most chemical reactions

A) absorb energy.
B) occur at rates that are independent of temperature.
C) are reversible.
D) produce precipitates.

Question 26

Sulfur has an atomic mass of 32 u and Avogadro's number is 6 × 10²³ formula units/mole. The number of sulfur atoms in 1 mole of sulfur is

A) 32.
B) 1.9 × 10²².
C) 6 × 10²³.
D) 1.9 × 10²⁵.

Question 27

Oxidation-reduction reactions involve the transfer between the reacting substances of

A) electrons.
B) H⁺ ions.
C) O_2- ions.
D) O₂ molecules.

Question 28

The yield of the product C in the reversible reaction A + B C + energy will decrease if

A) the temperature decreases.
B) the temperature increases.
C) the surface area of the substances increases.
D) the catalyst is changed appropriately.

Question 29

The number of moles of O₂ needed to react with 10 moles of C₂H₂ in the reaction 2C₂H₂ + 5O₂ → 4CO₂ + 2H₂O is

A) 5.
B) 10.
C) 25.
D) 50.

Question 30

When a gas reaction involves an increase in the number of molecules present, the yield can be increased by

A) increasing the pressure.
B) decreasing the pressure.
C) increasing the temperature.
D) decreasing the temperature.

Question 31

The number of moles of atomic oxygen in 2 moles of Ca₃PO₄)₂ is

A) 2.
B) 4.
C) 8.
D) 16.

Question 32

Chemical reactions in solution do not depend to any great extent upon

A) pressure.
B) temperature.
C) concentration.
D) catalysts.

Question 33

An enzyme is a

A) gasoline additive that reduces pollution.
B) constituent of natural gas.
C) solvent used in electrolysis.
D) biological catalyst.

Question 34

A storage battery stores

A) electrons.
B) electric current.
C) energy.
D) voltage.

Question 35

A chemical equilibrium occurs when the

A) mass of the products equals the mass of the reactants.
B) number of molecules of the products equals the number of molecules of the reactants.
C) concentration of the products equals the concentration of the reactants.
D) speed of the forward reaction equals the speed of the reverse reaction.

Question 36

When a hydrogen fuel cell produces an electric current,

A) it must be recharged periodically.
B) it must be heated.
C) it must have hydrogen added to it continuously.
D) it gives off carbon dioxide.

Question 37

Sulfur has an atomic mass of 32 u and Avogadro's number is 6 × 10²³ formula units/mole. The number of sulfur atoms in 1 g of sulfur is

A) 32.
B) 1.9 × 10²².
C) 6 × 10²³.
D) 1.9 × 10²⁵.

Question 38

Oxidation-reduction reactions are not involved in

A) electrolysis.
B) acid-base neutralization.
C) the operation of a storage battery.
D) the operation of a fuel cell.

Question 39

In the electrolysis of molten NaCl, the substance liberated at the positive electrode is

A) Cl^-.
B) Cl₂.
C) Na⁺.
D) Na.

Question 40

The number of moles of H₂O formed when 1 mole of O₂ reacts with C₅H₁₂ in the reaction C₅H₁₂ + 8O₂ → 5CO₂ + 6H₂O is

A) 3/4.
B) 4/3.
C) 6.
D) 8.