Introductory Chemistry

Steven S. Zumdahl, Donald J. DeCoste

Chapter 6

Chemical Reactions: An Introduction - all with Video Answers

Educators

Chapter Questions

Problem 1

How do we know when a chemical reaction is taking place? Can you think of an example of how each of the five senses (sight, hearing, taste, touch, smell) might be used in detecting when a chemical reaction has taken place?

Lizabeth Tumminello

Lizabeth Tumminello

Numerade Educator

Problem 2

These days many products are available to whiten teeth at home. Many of these products contain a peroxide that bleaches stains from the teeth. What evidence is there that the bleaching process is a chemical reaction?

Lizabeth Tumminello

Lizabeth Tumminello

Numerade Educator

Problem 3

Although these days many people have "self-cleaning" ovens, if your oven gets really dirty you may have to resort to one of the spray-on oven cleaner preparations sold in supermarkets. What evidence is there that such oven cleaners work by a chemical reaction?

Lizabeth Tumminello

Lizabeth Tumminello

Numerade Educator

Problem 4

Although this is no longer generally recommended, in the past, small cuts and abrasions on the skin were frequently cleaned using hydrogen peroxide solution. What evidence is there that treating a wound with hydrogen peroxide causes a chemical reaction to take place?

Dr. Satish Ingale

Dr. Satish Ingale

Numerade Educator

Problem 5

You have probably had the unpleasant experience of discovering that a flashlight battery has gotten old and begun to leak. Is there evidence that this change is due to a chemical reaction?

Lizabeth Tumminello

Lizabeth Tumminello

Numerade Educator

Problem 6

If you've ever left bread in a toaster too long, you know that the bread eventually burns and turns black. What evidence is there that this represents a chemical process?

Dr. Satish Ingale

Dr. Satish Ingale

Numerade Educator

Problem 7

What are the substances to the left of the arrow in a chemical equation called? To the right of the arrow? What does the arrow itself mean?

Noah Barguez-Arias

Noah Barguez-Arias

Numerade Educator

Problem 8

For the unbalanced chemical equation $\mathrm{HCl}(g)+\mathrm{O}_{2}(g) \rightarrow \mathrm{H}_{2} \mathrm{O}(g)+\mathrm{Cl}_{2}(g)$
a. list the reactant(s).
b. list the product(s).

Dr. Satish Ingale

Dr. Satish Ingale

Numerade Educator

Problem 9

In a chemical reaction, the total number of atoms present after the reaction is complete is (larger than/smaller than/the same as) the total number of atoms present before the reaction began.

Noah Barguez-Arias

Noah Barguez-Arias

Numerade Educator

Problem 10

What does "balancing" an equation accomplish?

Noah Barguez-Arias

Noah Barguez-Arias

Numerade Educator

Problem 11

Why are the physical states of the reactants and products often indicated when writing a chemical equation?

Noah Barguez-Arias

Noah Barguez-Arias

Numerade Educator

Problem 12

The notation " $(l)$ " after a substance's formula indicates it exists in the state.

Dr. Satish Ingale

Dr. Satish Ingale

Numerade Educator

Problem 13

A common experiment to determine the relative reactivity of metallic elements is to place a pure sample of one metal into an aqueous solution of a compound of another metallic element. If the pure metal you are adding is more reactive than the metallic element in the compound, then the pure metal will replace the metallic element in the compound. For example, if you place a piece of pure zinc metal into a solution of copper(II) sulfate, the zinc will slowly dissolve to produce zinc sulfate solution, and the copper(II) ion of the copper(II) sulfate will be converted to metallic copper. Write the unbalanced equation for this process.

Noah Barguez-Arias

Noah Barguez-Arias

Numerade Educator

Problem 14

A common lecture demonstration called "elephant's toothpaste" demonstrates the reaction of hydrogen peroxide producing water and oxygen gas. Write the unbalanced chemical equation for this process.

Dr. Satish Ingale

Dr. Satish Ingale

Numerade Educator

Problem 15

If a sample of pure hydrogen gas is ignited very carefully, the hydrogen burns gently, combining with the oxygen gas of the air to form water vapor. Write the unbalanced chemical equation for this reaction.

Cara Oneal

Numerade Educator

Problem 16

Liquid hydrazine, $\mathrm{N}_{2} \mathrm{H}_{4}$, has been used as a fuel for rockets. When the rocket is to be launched, a catalyst causes the liquid hydrazine to decompose quickly into elemental nitrogen and hydrogen gases. The rapid expansion of the product gases and the heat released by the reaction provide the thrust for the rocket. Write the unbalanced equation for the reaction of hydrazine to produce nitrogen and hydrogen gases.

Noah Barguez-Arias

Noah Barguez-Arias

Numerade Educator

Problem 17

If electricity of sufficient voltage is passed into a solution of potassium iodide in water, a reaction takes place in which elemental hydrogen gas and elemental iodine are produced, leaving a solution of potassium hydroxide. Write the unbalanced equation for this process.

Noah Barguez-Arias

Noah Barguez-Arias

Numerade Educator

Problem 18

Silver oxide may be decomposed by strong heating into silver metal and oxygen gas. Write the unbalanced chemical equation for this process.

HM

Heidi Montgomery

Numerade Educator

Problem 19

Elemental boron is produced in one industrial process by heating diboron trioxide with magnesium metal, also producing magnesium oxide as a by-product. Write the unbalanced chemical equation for this process.

Noah Barguez-Arias

Noah Barguez-Arias

Numerade Educator

Problem 20

Many over-the-counter antacid tablets are now formulated using calcium carbonate as the active ingredient, which enables such tablets to also be used as dietary calcium supplements. As an antacid for gastric hyperacidity, calcium carbonate reacts by combining with hydrochloric acid found in the stomach, producing a solution of calcium chloride, converting the stomach acid to water, and releasing carbon dioxide gas (which the person suffering from stomach problems may feel as a "burp"). Write the unbalanced chemical equation for this process.

Noah Barguez-Arias

Noah Barguez-Arias

Numerade Educator

Problem 21

Phosphorus trichloride is used in the manufacture of certain pesticides and may be synthesized by direct combination of its constituent elements. Write the unbalanced chemical equation for this process.

Noah Barguez-Arias

Noah Barguez-Arias

Numerade Educator

Problem 22

Pure silicon, which is needed in the manufacturing of electronic components, may be prepared by heating silicon dioxide (sand) with carbon at high temperatures, releasing carbon monoxide gas. Write the unbalanced chemical equation for this process.

Noah Barguez-Arias

Noah Barguez-Arias

Numerade Educator

Problem 23

Nitrous oxide gas (systematic name: dinitrogen monoxide) is used by some dental practitioners as an anesthetic. Nitrous oxide (and water vapor as by-product) can be produced in small quantities in the laboratory by careful heating of ammonium nitrate. Write the unbalanced chemical equation for this reaction.

Noah Barguez-Arias

Noah Barguez-Arias

Numerade Educator

Problem 24

Solid zinc is added to an aqueous solution containing dissolved hydrogen chloride to produce gaseous hydrogen that bubbles out of the solution and zinc chloride that remains dissolved in the water. Write the unbalanced chemical equation for this process.

Dr. Satish Ingale

Dr. Satish Ingale

Numerade Educator

Problem 25

Acetylene gas $\left(\mathrm{C}_{2} \mathrm{H}_{2}\right)$ is often used by plumbers, welders, and glass blowers because it burns in oxygen with an intensely hot flame. The products of the combustion of acetylene are carbon dioxide and water vapor. Write the unbalanced chemical equation for this process.

Cara Oneal

Numerade Educator

Problem 26

The burning of high-sulfur fuels has been shown to cause the phenomenon of "acid rain." When a high-sulfur fuel is burned, the sulfur is converted to sulfur dioxide $\left(\mathrm{SO}_{2}\right)$ and sulfur trioxide $\left(\mathrm{SO}_{3}\right)$. When sulfur dioxide and sulfur trioxide gas dissolve in water in the atmosphere, sulfurous acid and sulfuric acid are produced, respectively. Write the unbalanced chemical equations for the reactions of sulfur dioxide and sulfur trioxide with water.

Noah Barguez-Arias

Noah Barguez-Arias

Numerade Educator

Problem 27

The Group 2 metals $(\mathrm{Ba}, \mathrm{Ca}, \mathrm{Sr})$ can be produced in the elemental state by the reaction of their oxides with aluminum metal at high temperatures, also producing solid aluminum oxide as a byproduct. Write the unbalanced chemical equations for the reactions of barium oxide, calcium oxide, and strontium oxide with aluminum.

Cara Oneal

Numerade Educator

Problem 28

There are fears that the protective ozone layer around the earth is being depleted. Ozone, $\mathrm{O}_{3}$, is produced by the interaction of ordinary oxygen gas in the atmosphere with ultraviolet light and lightning discharges. The oxides of nitrogen (which are common in automobile exhaust gases), in particular, are known to decompose ozone. For example, gaseous nitric oxide (NO) reacts with ozone gas to produce nitrogen dioxide gas and oxygen gas. Write the unbalanced chemical equation for this process.

Dr. Satish Ingale

Dr. Satish Ingale

Numerade Educator

Problem 29

Carbon tetrachloride was widely used for many years as a solvent until its harmful properties became well established. Carbon tetrachloride may be prepared by the reaction of natural gas (methane, $\mathrm{CH}_{4}$ ) and elemental chlorine gas in the presence of ultraviolet light. Write the unbalanced chemical equation for this process.

Noah Barguez-Arias

Noah Barguez-Arias

Numerade Educator

Problem 30

When elemental phosphorus, $\mathrm{P}_{4},$ burns in oxygen gas, it produces an intensely bright light, a great deal of heat, and massive clouds of white solid phosphorus(V) oxide $\left(\mathrm{P}_{2} \mathrm{O}_{5}\right)$ product. Given these properties, it is not surprising that phosphorus has been used to manufacture incendiary bombs for warfare. Write the unbalanced equation for the reaction of phosphorus with oxygen gas to produce phosphorus(V) oxide.

Noah Barguez-Arias

Noah Barguez-Arias

Numerade Educator

Problem 31

Calcium oxide is sometimes very challenging to store in the chemistry laboratory. This compound reacts with moisture in the air and is converted to calcium hydroxide. If a bottle of calcium oxide is left on the shelf too long, it gradually absorbs moisture from the humidity in the laboratory. Eventually the bottle cracks and spills the calcium hydroxide that has been produced. Write the unbalanced chemical equation for this process.

Noah Barguez-Arias

Noah Barguez-Arias

Numerade Educator

Problem 32

Although they were formerly called the inert gases, the heavier elements of Group 8 do form relatively stable compounds. For example, at high temperatures in the presence of an appropriate catalyst, xenon gas will combine directly with fluorine gas to produce solid xenon tetrafluoride. Write the unbalanced chemical equation for this process.

Noah Barguez-Arias

Noah Barguez-Arias

Numerade Educator

Problem 33

The element tin often occurs in nature as the oxide, $\mathrm{SnO}_{2}$. To produce pure tin metal from this sort of tin ore, the ore usually is heated with coal (carbon). This produces pure molten tin, with the carbon being removed from the reaction system as the gaseous byproduct carbon monoxide. Write the unbalanced equation for this process.

Noah Barguez-Arias

Noah Barguez-Arias

Numerade Educator

Problem 34

Nitric acid, $\mathrm{HNO}_{3}$, can be produced by reacting high-pressure ammonia gas with oxygen gas at around 750 " in the presence of a platinum catalyst. Water is a by-product of the reaction. Write the unbalanced chemical equation for this process.

Dr. Satish Ingale

Dr. Satish Ingale

Numerade Educator

Problem 35

When balancing chemical equations, beginning students are often tempted to change the numbers within a formula (the subscripts) to balance the equation. Why is this never permitted? What effect does changing a subscript have?

Marisa A

Numerade Educator

Problem 36

The "Chemistry in Focus" segment The Beetle That Shoots Straight discusses the bombardier beetle and the chemical reaction of the decomposition of hydrogen peroxide.
$$\mathrm{H}_{2} \mathrm{O}_{2}(a q) \rightarrow \mathrm{H}_{2} \mathrm{O}(l)+\mathrm{O}_{2}(g)$$
The balanced equation given in the segment is
$$2 \mathrm{H}_{2} \mathrm{O}_{2}(a q) \rightarrow 2 \mathrm{H}_{2} \mathrm{O}(l)+\mathrm{O}_{2}(g)$$
Why can't we balance the equation in the following way?
$$\mathrm{H}_{2} \mathrm{O}_{2}(a q) \rightarrow \mathrm{H}_{2}(g)+\mathrm{O}_{2}(g)$$
Use molecular-level pictures like those in Section 6.3 to support your answer.

Rebecca Wallace

Rebecca Wallace

Numerade Educator

Problem 37

Balance each of the following chemical equations.
a. $\mathrm{FeCl}_{3}(a q)+\mathrm{KOH}(a q) \rightarrow \mathrm{Fe}(\mathrm{OH})_{3}(s)+\mathrm{KCl}(a q)$
b. $\mathrm{Pb}\left(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}\right)_{2}(a q)+\mathrm{KI}(a q) \rightarrow \mathrm{PbI}_{2}(s)+\mathrm{KC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}(a q)$
c. $\mathrm{P}_{4} \mathrm{O}_{10}(s)+\mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{H}_{3} \mathrm{PO}_{4}(a q)$
d. $\mathrm{Li}_{2} \mathrm{O}(s)+\mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{LiOH}(a q)$
e. $\operatorname{MnO}_{2}(s)+\mathrm{C}(s) \rightarrow \operatorname{Mn}(s)+\mathrm{CO}_{2}(g)$
f. $\mathrm{Sb}(s)+\mathrm{Cl}_{2}(g) \rightarrow \mathrm{SbCl}_{3}(s)$
g. $\mathrm{CH}_{4}(g)+\mathrm{H}_{2} \mathrm{O}(g) \rightarrow \mathrm{CO}(g)+\mathrm{H}_{2}(g)$
h. $\mathrm{FeS}(s)+\mathrm{HCl}(a q) \rightarrow \mathrm{FeCl}_{2}(a q)+\mathrm{H}_{2} \mathrm{~S}(g)$

Julie Guaglianone

Julie Guaglianone

Numerade Educator

Problem 38

Balance the equation for the reaction of potassium with water.
$$\mathrm{K}(s)+\mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{H}_{2}(g)+\mathrm{KOH}(a q)$$

Dr. Satish Ingale

Dr. Satish Ingale

Numerade Educator

Problem 38

Balance the equation for the reaction of potassium with water.
$$\mathrm{K}(s)+\mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{H}_{2}(g)+\mathrm{KOH}(a q)$$

Dr. Satish Ingale

Dr. Satish Ingale

Numerade Educator

Problem 39

Balance each of the following chemical equations.
a. $\mathrm{K}_{2} \mathrm{SO}_{4}(a q)+\mathrm{BaCl}_{2}(a q) \rightarrow \mathrm{BaSO}_{4}(s)+\mathrm{KCl}(a q)$
b. $\mathrm{Fe}(s)+\mathrm{H}_{2} \mathrm{O}(g) \rightarrow \mathrm{FeO}(s)+\mathrm{H}_{2}(g)$
c. $\mathrm{NaOH}(a q)+\mathrm{HClO}_{4}(a q) \rightarrow \mathrm{NaClO}_{4}(a q)+\mathrm{H}_{2} \mathrm{O}(l)$
d. $\operatorname{Mg}(s)+\operatorname{Mn}_{2} \mathrm{O}_{3}(s) \rightarrow \mathrm{MgO}(s)+\operatorname{Mn}(s)$
e. $\mathrm{KOH}(s)+\mathrm{KH}_{2} \mathrm{PO}_{4}(a q) \rightarrow \mathrm{K}_{3} \mathrm{PO}_{4}(a q)+\mathrm{H}_{2} \mathrm{O}(l)$
f. $\mathrm{NO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(l)+\mathrm{O}_{2}(g) \rightarrow \mathrm{HNO}_{3}(a q)$
g. $\mathrm{BaO}_{2}(s)+\mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{Ba}(\mathrm{OH})_{2}(a q)+\mathrm{O}_{2}(g)$
h. $\mathrm{NH}_{3}(g)+\mathrm{O}_{2}(g) \rightarrow \mathrm{NO}(g)+\mathrm{H}_{2} \mathrm{O}(l)$

Julie Guaglianone

Julie Guaglianone

Numerade Educator

Problem 40

Balance each of the following chemical equations.
a. $\mathrm{Na}_{2} \mathrm{SO}_{4}(a q)+\mathrm{CaCl}_{2}(a q) \rightarrow \mathrm{CaSO}_{4}(s)+\mathrm{NaCl}(a q)$
b. $\mathrm{Fe}(s)+\mathrm{H}_{2} \mathrm{O}(g) \rightarrow \mathrm{Fe}_{3} \mathrm{O}_{4}(s)+\mathrm{H}_{2}(g)$
c. $\mathrm{Ca}(\mathrm{OH})_{2}(a q)+\mathrm{HCl}(a q) \rightarrow \mathrm{CaCl}_{2}(a q)+\mathrm{H}_{2} \mathrm{O}(l)$
d. $\operatorname{Br}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(l)+\mathrm{SO}_{2}(g) \rightarrow \mathrm{HBr}(a q)+\mathrm{H}_{2} \mathrm{SO}_{4}(a q)$
e. $\mathrm{NaOH}(s)+\mathrm{H}_{3} \mathrm{PO}_{4}(a q) \rightarrow \mathrm{Na}_{3} \mathrm{PO}_{4}(a q)+\mathrm{H}_{2} \mathrm{O}(l)$
f. $\operatorname{NaNO}_{3}(s) \rightarrow \operatorname{NaNO}_{2}(s)+\mathrm{O}_{2}(g)$
g. $\mathrm{Na}_{2} \mathrm{O}_{2}(s)+\mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{NaOH}(a q)+\mathrm{O}_{2}(g)$
h $\mathrm{i}(s)+\mathrm{S}_{8}(s) \rightarrow \mathrm{Si}_{2} \mathrm{~S}_{4}(s)$

Julie Guaglianone

Julie Guaglianone

Numerade Educator

Problem 40

Balance each of the following chemical equations.
a. $\mathrm{Na}_{2} \mathrm{SO}_{4}(a q)+\mathrm{CaCl}_{2}(a q) \rightarrow \mathrm{CaSO}_{4}(s)+\mathrm{NaCl}(a q)$
b. $\mathrm{Fe}(s)+\mathrm{H}_{2} \mathrm{O}(g) \rightarrow \mathrm{Fe}_{3} \mathrm{O}_{4}(s)+\mathrm{H}_{2}(g)$
c. $\mathrm{Ca}(\mathrm{OH})_{2}(a q)+\mathrm{HCl}(a q) \rightarrow \mathrm{CaCl}_{2}(a q)+\mathrm{H}_{2} \mathrm{O}(l)$
d. $\mathrm{Br}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(l)+\mathrm{SO}_{2}(g) \rightarrow \mathrm{HBr}(a q)+\mathrm{H}_{2} \mathrm{SO}_{4}(a q)$
e. $\mathrm{NaOH}(s)+\mathrm{H}_{3} \mathrm{PO}_{4}(a q) \rightarrow \mathrm{Na}_{3} \mathrm{PO}_{4}(a q)+\mathrm{H}_{2} \mathrm{O}(l)$
f. $\mathrm{NaNO}_{3}(s) \rightarrow \mathrm{NaNO}_{2}(s)+\mathrm{O}_{2}(g)$
g. $\mathrm{Na}_{2} \mathrm{O}_{2}(s)+\mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{NaOH}(a q)+\mathrm{O}_{2}(g)$
h. $\mathrm{Si}(s)+\mathrm{S}_{8}(s) \rightarrow \mathrm{Si}_{2} \mathrm{~S}_{4}(s)$

Julie Guaglianone

Julie Guaglianone

Numerade Educator

Problem 41

Balance each of the following chemical equations.
a. $\mathrm{Fe}_{3} \mathrm{O}_{4}(s)+\mathrm{H}_{2}(g) \rightarrow \mathrm{Fe}(l)+\mathrm{H}_{2} \mathrm{O}(g)$
b. $\mathrm{K}_{2} \mathrm{SO}_{4}(a q)+\mathrm{BaCl}_{2}(a q) \rightarrow \mathrm{BaSO}_{4}(s)+\mathrm{KCl}(a q)$
c. $\mathrm{HCl}(a q)+\mathrm{FeS}(s) \rightarrow \mathrm{FeCl}_{2}(a q)+\mathrm{H}_{2} \mathrm{~S}(g)$
d. $\mathrm{Br}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(l)+\mathrm{SO}_{2}(g) \rightarrow \mathrm{HBr}(a q)+\mathrm{H}_{2} \mathrm{SO}_{4}(a q)$
e. $\mathrm{CS}_{2}(l)+\mathrm{Cl}_{2}(g) \rightarrow \mathrm{CCl}_{4}(l)+\mathrm{S}_{2} \mathrm{Cl}_{2}(g)$
f. $\mathrm{Cl}_{2} \mathrm{O}_{7}(g)+\mathrm{Ca}(\mathrm{OH})_{2}(a q) \rightarrow \mathrm{Ca}\left(\mathrm{ClO}_{4}\right)_{2}(a q)+\mathrm{H}_{2} \mathrm{O}(l)$
g. $\operatorname{PBr}_{3}(l)+\mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{H}_{3} \mathrm{PO}_{3}(a q)+\mathrm{HBr}(g)$
h. $\mathrm{Ba}\left(\mathrm{ClO}_{3}\right)_{2}(s) \rightarrow \mathrm{BaCl}_{2}(s)+\mathrm{O}_{2}(s)$

Julie Guaglianone

Julie Guaglianone

Numerade Educator

Problem 42

Balance each of the following chemical equations.
a. $\mathrm{NaCl}(s)+\mathrm{SO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(g)+\mathrm{O}_{2}(g) \rightarrow \mathrm{Na}_{2} \mathrm{SO}_{4}(s)+\mathrm{HCl}(g)$
b. $\operatorname{Br}_{2}(l)+\mathrm{I}_{2}(s) \rightarrow \operatorname{IBr}_{3}(s)$
c. $\mathrm{Ca}_{3} \mathrm{~N}_{2}(s)+\mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{Ca}(\mathrm{OH})_{2}(a q)+\mathrm{PH}_{3}(g)$
d. $\mathrm{BF}_{3}(g)+\mathrm{H}_{2} \mathrm{O}(g) \rightarrow \mathrm{B}_{2} \mathrm{O}_{3}(s)+\mathrm{HF}(g)$
e. $\mathrm{SO}_{2}(g)+\mathrm{Cl}_{2}(g) \rightarrow \mathrm{SOCl}_{2}(l)+\mathrm{Cl}_{2} \mathrm{O}(g)$
f. $\mathrm{Li}_{2} \mathrm{O}(s)+\mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{LiOH}(a q)$
g. $\operatorname{Mg}(s)+\mathrm{CuO}(s) \rightarrow \mathrm{MgO}(s)+\mathrm{Cu}(l)$
h. $\mathrm{Fe}_{3} \mathrm{O}_{4}(s)+\mathrm{H}_{2}(g) \rightarrow \mathrm{Fe}(l)+\mathrm{H}_{2} \mathrm{O}(g)$

Julie Guaglianone

Julie Guaglianone

Numerade Educator

Problem 43

Balance each of the following chemical equations.
a. $\mathrm{KO}_{2}(s)+\mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{KOH}(a q)+\mathrm{O}_{2}(g)+\mathrm{H}_{2} \mathrm{O}_{2}(a q)$
b. $\mathrm{Fe}_{2} \mathrm{O}_{3}(s)+\mathrm{HNO}_{3}(a q) \rightarrow \mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{3}(a q)+\mathrm{H}_{2} \mathrm{O}(l)$
c. $\mathrm{NH}_{3}(g)+\mathrm{O}_{2}(g) \rightarrow \mathrm{NO}(g)+\mathrm{H}_{2} \mathrm{O}(g)$
d. $\mathrm{PCl}_{5}(l)+\mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{H}_{3} \mathrm{PO}_{4}(a q)+\mathrm{HCl}(g)$
e. $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}(l)+\mathrm{O}_{2}(g) \rightarrow \mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(l)$
f. $\mathrm{CaO}(s)+\mathrm{C}(s) \rightarrow \mathrm{CaC}_{2}(s)+\mathrm{CO}_{2}(g)$
g. $\operatorname{MoS}_{2}(s)+\mathrm{O}_{2}(g) \rightarrow \mathrm{MoO}_{3}(s)+\mathrm{SO}_{2}(g)$
h. $\mathrm{FeCO}_{3}(s)+\mathrm{H}_{2} \mathrm{CO}_{3}(a q) \rightarrow \mathrm{Fe}\left(\mathrm{HCO}_{3}\right)_{2}(a q)$

Oluwapelumi Kolawole

Oluwapelumi Kolawole

Numerade Educator

Problem 44

Balance each of the following chemical equations.
a. $\mathrm{Ba}\left(\mathrm{NO}_{3}\right)_{2}(a q)+\mathrm{Na}_{2} \mathrm{CrO}_{4}(a q) \rightarrow \mathrm{BaCrO}_{4}(s)+\mathrm{NaNO}_{3}(a q)$
b. $\mathrm{PbCl}_{2}(a q)+\mathrm{K}_{2} \mathrm{SO}_{4}(a q) \rightarrow \mathrm{PbSO}_{4}(s)+\mathrm{KCl}(a q)$
c. $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}(l)+\mathrm{O}_{2}(g) \rightarrow \mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(l)$
d. $\mathrm{CaC}_{2}(s)+\mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{Ca}(\mathrm{OH})_{2}(s)+\mathrm{C}_{2} \mathrm{H}_{2}(g)$
e. $\operatorname{Sr}(s)+\mathrm{HNO}_{3}(a q) \rightarrow \operatorname{Sr}\left(\mathrm{NO}_{3}\right)_{2}(a q)+\mathrm{H}_{2}(g)$
f. $\mathrm{BaO}_{2}(s)+\mathrm{H}_{2} \mathrm{SO}_{4}(a q) \rightarrow \mathrm{BaSO}_{4}(s)+\mathrm{H}_{2} \mathrm{O}_{2}(a q)$
g. $\operatorname{AsI}_{3}(s) \rightarrow \operatorname{As}(s)+\mathrm{I}_{2}(s)$
h. $\mathrm{CuSO}_{4}(a q)+\mathrm{KI}(s) \rightarrow \mathrm{CuI}(s)+\mathrm{I}_{2}(s)+\mathrm{K}_{2} \mathrm{SO}_{4}(a q)$

Julie Guaglianone

Julie Guaglianone

Numerade Educator

Problem 45

Acetylene gas, $\mathrm{C}_{2} \mathrm{H}_{2},$ is used in welding because it generates an extremely hot flame when it is combusted with oxygen. The heat generated is sufficient to melt the metals being welded together. Carbon dioxide gas and water vapor are the chemical products of this reaction. Write the unbalanced chemical equation for the reaction of acetylene with oxygen.

Julie Guaglianone

Julie Guaglianone

Numerade Educator

Problem 46

When balancing a chemical equation, which of the following statements is false?
a. Subscripts in the reactants must be conserved in the products.
b. Coefficients are used to balance the atoms on both sides.
c. The law of conservation of matter must be followed.
d. Phases are often shown for each compound but are not critical to balancing an equation.

Dr. Satish Ingale

Dr. Satish Ingale

Numerade Educator

Problem 47

Crude gunpowders often contain a mixture of potassium nitrate and charcoal (carbon). When such a mixture is heated until reaction occurs, a solid residue of potassium carbonate is produced. The explosive force of the gunpowder comes from the fact that two gases are also produced (carbon monoxide and nitrogen), which increase in volume with great force and speed. Write the unbalanced chemical equation for the process.

Cara Oneal

Numerade Educator

Problem 48

The following demonstration takes place in a two-step process: First, solid calcium carbide $\left(\mathrm{CaC}_{2}\right)$ reacts with liquid water to produce acetylene gas $\left(\mathrm{C}_{2} \mathrm{H}_{2}\right)$ and aqueous calcium hydroxide. Second, the acetylene gas produced is then ignited with a match, causing the combustion reaction of acetylene with oxygen gas to produce gaseous carbon dioxide and gaseous water. Write the balanced equation for each reaction that is occurring.

Dr. Satish Ingale

Dr. Satish Ingale

Numerade Educator

Problem 49

Methanol (methyl alcohol), $\mathrm{CH}_{3} \mathrm{OH}$, is a very important industrial chemical. Formerly, methanol was prepared by heating wood to high temperatures in the absence of air. The complex compounds present in wood are degraded by this process into a charcoal residue and a volatile portion that is rich in methanol. Today, methanol is instead synthesized from carbon monoxide and elemental hydrogen. Write the balanced chemical equation for this latter process.

Julie Guaglianone

Julie Guaglianone

Numerade Educator

Problem 50

The Hall process is an important method by which pure aluminum is prepared from its oxide (alumina, $\mathrm{Al}_{2} \mathrm{O}_{3}$ ) by indirect reaction with graphite (carbon). Balance the following equation, which is a simplified representation of this process.
$$\mathrm{Al}_{2} \mathrm{O}_{3}(s)+\mathrm{C}(s) \rightarrow \mathrm{Al}(s)+\mathrm{CO}_{2}(g)$$

Julie Guaglianone

Julie Guaglianone

Numerade Educator

Problem 51

Iron oxide ores, commonly a mixture of $\mathrm{FeO}$ and $\mathrm{Fe}_{2} \mathrm{O}_{3}$, are given the general formula $\mathrm{Fe}_{3} \mathrm{O}_{4}$. They yield elemental iron when heated to a very high temperature with either carbon monoxide or elemental hydrogen. Balance the following equations for these processes.
$$\begin{aligned}\mathrm{Fe}_{3} \mathrm{O}_{4}(s)+\mathrm{H}_{2}(g) & \rightarrow \mathrm{Fe}(s)+\mathrm{H}_{2} \mathrm{O}(g) \\
\mathrm{Fe}_{3} \mathrm{O}_{4}(s)+\mathrm{CO}(g) & \rightarrow \mathrm{Fe}(s)+\mathrm{CO}_{2}(g)\end{aligned}$$

Cara Oneal

Numerade Educator

Problem 52

True or false? Coefficients can be fractions when balancing a chemical equation. Whether true or false, explain why this can or cannot occur.

Lottie Adams

Numerade Educator

Problem 53

When steel wool (iron) is heated in pure oxygen gas, the steel wool bursts into flame and a fine powder consisting of a mixture of iron oxides ( $\mathrm{FeO}$ and $\mathrm{Fe}_{2} \mathrm{O}_{3}$ ) forms. Write separate unbalanced equations for the reaction of iron with oxygen to give each of these products.

Julie Guaglianone

Julie Guaglianone

Numerade Educator

Problem 54

One method of producing hydrogen peroxide is to add barium peroxide to water. A precipitate of barium oxide forms, which may then be filtered off to leave a solution of hydrogen peroxide. Write the balanced chemical equation for this process.

Julie Guaglianone

Julie Guaglianone

Numerade Educator

Problem 55

When elemental boron, $\mathrm{B}$, is burned in oxygen gas, the product is diboron trioxide. If the diboron trioxide is then reacted with a measured quantity of water, it reacts with the water to form what is commonly known as boric acid, $\mathrm{B}(\mathrm{OH})_{3} .$ Write a balanced chemical equation for each of these processes.

Julie Guaglianone

Julie Guaglianone

Numerade Educator

Problem 56

A common experiment in introductory chemistry courses involves heating a weighed mixture of potassium chlorate, $\mathrm{KClO}_{3}$, and potassium chloride. Potassium chlorate decomposes when heated, producing potassium chloride and evolving oxygen gas. By measuring the volume of oxygen gas produced in this experiment, students can calculate the relative percentage of $\mathrm{KClO}_{3}$ and $\mathrm{KCl}$ in the original mixture. Write the balanced chemical equation for this process.

Julie Guaglianone

Julie Guaglianone

Numerade Educator

Problem 57

A common demonstration in chemistry courses involves adding a tiny speck of manganese(IV) oxide to a concentrated hydrogen peroxide, $\mathrm{H}_{2} \mathrm{O}_{2},$ solution. Hydrogen peroxide is unstable, and it decomposes quite spectacularly under these conditions to produce oxygen gas and steam (water vapor). Manganese(IV) oxide is a catalyst for the decomposition of hydrogen peroxide and is not consumed in the reaction. Write the balanced equation for the decomposition reaction of hydrogen peroxide.

Julie Guaglianone

Julie Guaglianone

Numerade Educator

Problem 58

Write a balanced chemical equation for the complete combustion of pentene, $\mathrm{C}_{7} \mathrm{H}_{14} .$ In combustion, pentene reacts with oxygen to produce carbon dioxide and water.

Dr. Satish Ingale

Dr. Satish Ingale

Numerade Educator

Problem 59

Glass is a mixture of several compounds, but a major constituent of most glass is calcium silicate, $\mathrm{CaSiO}_{3}$. Glass can be etched by treatment with hydrogen fluoride: HF attacks the calcium silicate of the glass, producing gaseous and water-soluble products (which can be removed by washing the glass). Balance the following equation fo the reaction of hydrogen fluoride with calcium silicate.
$$
\mathrm{CaSiO}_{3}(s)+\mathrm{HF}(g) \rightarrow \mathrm{CaF}_{2}(a q)+\mathrm{SiF}_{4}(g)+\mathrm{H}_{2} \mathrm{O}(l)
$$

Dr. Satish Ingale

Dr. Satish Ingale

Numerade Educator

Problem 60

Balance the following chemical equation.
$$\operatorname{LiAlH}_{4}(s)+\mathrm{AlCl}_{3}(s) \rightarrow \mathrm{AlH}_{3}(s)+\mathrm{LiCl}(s)$$

Dr. Satish Ingale

Dr. Satish Ingale

Numerade Educator

Problem 61

If you had a "sour stomach," you might try an over-the-counter antacid tablet to relieve the problem. Can you think of evidence that the action of such an antacid is a chemical reaction?

Julie Guaglianone

Julie Guaglianone

Numerade Educator

Problem 62

When iron wire is heated in the presence of sulfur, the iron soon begins to glow, and a chunky, blue-black mass of iron(II) sulfide is formed. Write the unbalanced chemical equation for this reaction.

Julie Guaglianone

Julie Guaglianone

Numerade Educator

Problem 63

When finely divided solid sodium is dropped into a flask containing chlorine gas, an explosion occurs and a fine powder of sodium chloride is deposited on the walls of the flask. Write the unbalanced chemical equation for this process.

Julie Guaglianone

Julie Guaglianone

Numerade Educator

Problem 64

If aqueous solutions of potassium chromate and barium chloride are mixed, a bright yellow solid (barium chromate) forms and settle out of the mixture, leaving potassium chloride in solution. Write a balanced chemical equation for this process.

Dr. Satish Ingale

Dr. Satish Ingale

Numerade Educator

Problem 65

When hydrogen sulfide, $\mathrm{H}_{2} \mathrm{~S}$, gas is bubbled through a solution of lead(II) nitrate, $\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}$, a black precipitate of lead(II) sulfide, $\mathrm{PbS},$ forms, and nitric acid, $\mathrm{HNO}_{3},$ is produced. Write the unbalanced chemical equation for this reaction.

Dr. Satish Ingale

Dr. Satish Ingale

Numerade Educator

Problem 66

If an electric current is passed through aqueous solutions of sodium chloride, sodium bromide, and sodium iodide, the elemental halogens are produced at one electrode in each case, with hydrogen gas being evolved at the other electrode. If the liquid is then evaporated from the mixture, a residue of sodium hydroxide remains. Write balanced chemical equations for these electrolysis reactions.

Julie Guaglianone

Julie Guaglianone

Numerade Educator

Problem 67

When a strip of magnesium metal is heated in oxygen, it bursts into an intensely white flame and produces a finely powdered dust of magnesium oxide. Write the unbalanced chemical equation for this process.

AD

Attila Dos Santos

Numerade Educator

Problem 68

Which of the following statements is false for the reaction of hydrogen gas with oxygen gas to produce water? $(a, b,$ and $c$ represent coefficients) $$a \mathrm{H}_{2}(g)+b \mathrm{O}_{2}(g) \rightarrow c \mathrm{H}_{2} \mathrm{O}(g)$$
a. The ratio of " $a / c "$ must always equal one.
b. The sum of $a+b+c$ equals 5 when balanced using the lowest whole-number coefficients.
c. Coefficient $b$ can equal $1 / 2$ because coefficients can be fractions.
d. The number of atoms on the reactant side must equal the number of atoms on the product side.
e. Subscripts can be changed to balance this equation, just as they

Dr. Satish Ingale

Dr. Satish Ingale

Numerade Educator

Problem 69

When solid red phosphorus, $\mathrm{P}_{4},$ is burned in air, the phosphorus combines with oxygen, producing a choking cloud of tetraphosphorus decoxide. Write the unbalanced chemical equation for this reaction.

Julie Guaglianone

Julie Guaglianone

Numerade Educator

Problem 70

When copper(II) oxide is boiled in an aqueous solution of sulfuric acid, a strikingly blue solution of copper(II) sulfate forms along with additional water. Write the unbalanced chemical equation for this reaction.

Julie Guaglianone

Julie Guaglianone

Numerade Educator

Problem 71

When lead(II) sulfide is heated to high temperatures in a stream of pure oxygen gas, solid lead(II) oxide forms with the release of gaseous sulfur dioxide. Write the unbalanced chemical equation for this reaction.

Ali Mcdillon

Numerade Educator

Problem 72

Which of the following statements about chemical reactions is false?
a. When balancing a chemical equation, all subscripts must be conserved.
b. When one coefficient is doubled, the rest of the coefficients in the balanced equation must also be doubled.
c. The subscripts in a balanced equation tell us the number of atoms in a molecule.
d. The phases in a chemical reaction tell us the nature of the reactants and products.

Dr. Satish Ingale

Dr. Satish Ingale

Numerade Educator

Problem 73

Balance each of the following chemical equations.
a. $\mathrm{Cl}_{2}(g)+\mathrm{KBr}(a q) \rightarrow \mathrm{Br}_{2}(l)+\mathrm{KCl}(a q)$
b. $\operatorname{Cr}(s)+\mathrm{O}_{2}(g) \rightarrow \mathrm{Cr}_{2} \mathrm{O}_{3}(s)$
c. $\mathrm{P}_{4}(s)+\mathrm{H}_{2}(g) \rightarrow \mathrm{PH}_{3}(g)$ d. $\mathrm{Al}(s)+\mathrm{H}_{2} \mathrm{SO}_{4}(a q) \rightarrow \mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}(a q)+\mathrm{H}_{2}(g)$
e. $\mathrm{PCl}_{3}(l)+\mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{H}_{3} \mathrm{PO}_{3}(a q)+\mathrm{HCl}(a q)$
$\mathrm{f} \cdot \mathrm{SO}_{2}(g)+\mathrm{O}_{2}(g) \rightarrow \mathrm{SO}_{3}(g)$
g. $\mathrm{C}_{7} \mathrm{H}_{16}(l)+\mathrm{O}_{2}(g) \rightarrow \mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(g)$
h. $\mathrm{C}_{2} \mathrm{H}_{6}(g)+\mathrm{O}_{2}(g) \rightarrow \mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(g)$

Dr. Satish Ingale

Dr. Satish Ingale

Numerade Educator

Problem 74

Balance the following chemical equation:
$$\mathrm{CuSO}_{4}(a q)+\mathrm{KI}(s) \rightarrow \mathrm{CuI}(s)+\mathrm{I}_{2}(s)+\mathrm{K}_{2} \mathrm{SO}_{4}(a q)$$

Dr. Satish Ingale

Dr. Satish Ingale

Numerade Educator

Problem 75

Balance each of the following chemical equations.
a. $\mathrm{SiCl}_{4}(l)+\mathrm{Mg}(s) \rightarrow \mathrm{Si}(s)+\mathrm{MgCl}_{2}(s)$
b. $\mathrm{NO}(g)+\mathrm{Cl}_{2}(g) \rightarrow \mathrm{NOCl}(g)$
c. $\operatorname{MnO}_{2}(s)+\operatorname{Al}(s) \rightarrow \operatorname{Mn}(s)+\mathrm{Al}_{2} \mathrm{O}_{3}(s)$
d. $\operatorname{Cr}(s)+\mathrm{S}_{8}(s) \rightarrow \mathrm{Cr}_{2} \mathrm{~S}_{3}(s)$
e. $\mathrm{NH}_{3}(g)+\mathrm{F}_{2}(g) \rightarrow \mathrm{NH}_{4} \mathrm{~F}(s)+\mathrm{NF}_{3}(g)$
f. $\mathrm{Ag}_{2} \mathrm{~S}(s)+\mathrm{H}_{2}(g) \rightarrow \mathrm{Ag}(s)+\mathrm{H}_{2} \mathrm{~S}(g)$
g. $\mathrm{O}_{2}(g) \rightarrow \mathrm{O}_{3}(g)$
h. $\mathrm{Na}_{2} \mathrm{SO}_{3}(a q)+\mathrm{S}_{8}(s) \rightarrow \mathrm{Na}_{2} \mathrm{~S}_{2} \mathrm{O}_{3}(a q)$

Dr. Satish Ingale

Dr. Satish Ingale

Numerade Educator

Problem 76

Using different shapes to distinguish between different elements, draw a balanced equation for the following reaction at the microscopic level.
$$\mathrm{NH}_{3}(g)+\mathrm{O}_{2}(g) \rightarrow \mathrm{NO}(g)+\mathrm{H}_{2} \mathrm{O}(g)$$

Dr. Satish Ingale

Dr. Satish Ingale

Numerade Educator

Problem 77

Which of the following statements about chemical equations is (are) true?
a. When balancing a chemical equation, you can never change the coefficient in front of any chemical formula.
b. The coefficients in a balanced chemical equation refer to the number of grams of reactants and products.
c. In a chemical equation, the reactants are on the right, and the products are on the left.
d. When balancing a chemical equation, you can never change the subscripts of any chemical formula.
e. In chemical reactions, matter is neither created nor destroyed, so a chemical equation must have the same number of atoms on both sides of the equation.

Ronald Prasad

Numerade Educator

Problem 78

Balance the following chemical equations.
$$\begin{array}{l}\mathrm{Fe}(s)+\mathrm{O}_{2}(g) \rightarrow \mathrm{Fe}_{2} \mathrm{O}_{3}(s) \\\mathrm{PbO}_{2}(s) \rightarrow \mathrm{PbO}(s)+\mathrm{O}_{2}(g) \\\mathrm{H}_{2} \mathrm{O}_{2}(l) \rightarrow \mathrm{O}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(l)
\end{array}$$

Dr. Satish Ingale

Dr. Satish Ingale

Numerade Educator

Problem 79

Balance the following chemical equations.
$\mathrm{MnO}_{2}(s)+\mathrm{CO}(g) \rightarrow \mathrm{Mn}_{2} \mathrm{O}_{3}(a q)+\mathrm{CO}_{2}(g)$
$\mathrm{Al}(s)+\mathrm{H}_{2} \mathrm{SO}_{4}(a q) \rightarrow \mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}(a q)+\mathrm{H}_{2}(g)$
$\mathrm{C}_{4} \mathrm{H}_{10}(g)+\mathrm{O}_{2}(g) \rightarrow \mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(l)$
$\mathrm{NH}_{4} \mathrm{I}(a q)+\mathrm{Cl}_{2}(g) \rightarrow \mathrm{NH}_{4} \mathrm{Cl}(a q)+\mathrm{I}_{2}(g)$
$\mathrm{KOH}(a q)+\mathrm{H}_{2} \mathrm{SO}_{4}(a q) \rightarrow \mathrm{K}_{2} \mathrm{SO}_{4}(a q)+\mathrm{H}_{2} \mathrm{O}(l)$

Dr. Satish Ingale

Dr. Satish Ingale

Numerade Educator