Chemical Quantities and Reactions

In each of the following, identify the reactant that is oxidized and the reactant that is reduced: 

a. $Zn\left(s\right) + C{l}_2\left(g\right)\to ZnC{l}_2\left(s\right)$

b.${\mathrm{CI}}_2\left(\mathrm{g}\right) + 2\mathrm{NaBr}\left(\mathrm{aq}\right)\to 2\mathrm{NaCl}\left(\mathrm{aq}\right) + {\mathrm{Br}}_2\left(\mathrm{l}\right)$

c.$2\mathrm{PbO}\left(\mathrm{s}\right) \to 2\mathrm{Pb}\left(\mathrm{s}\right) + {\mathrm{O}}_2\left(\mathrm{g}\right)$

d.$2\mathrm{Fe} \left(\mathrm{aq}\right) + {\mathrm{Sn}}^{2+}\left(\mathrm{aq}\right) \to 2{\mathrm{Fe}}^{2+} \left(\mathrm{aq}\right) + {\mathrm{Sn}}^{4+} \left(\mathrm{aq}\right)$

What is mole $?$

What is Avogadro's number $?$

Calculate each of the following:
a. Number of $C$ atoms in $0.500$ mole of $C$.
b. Number of $S{O}_2$ molecules in $1.28$ moles of $S{O}_2$
c. Moles of $Fe$ in $5.22\times {10}^{22}$  atoms of $Fe$.
d. Moles of $C_2{H}_{6}O$ in $8.50\times {10}^{24}$ molecules of $C_2{H}_{6}O$.

Calculate each of the following: 

1. number of $\mathrm{Li}$ atoms in $4.5$ moles of $\mathrm{Li}$
2.  number of ${\mathrm{CO}}_2$ molecules in $0.0180$ mole of ${\mathrm{CO}}_2$
3. moles of $\mathrm{Cu}$ in $7.8\times {10}^{21}$ atoms of Cu
4. moles of ${\mathrm{C}}_2{\mathrm{H}}_6$ in $3.75\times {10}^{23}$ molecules of ${\mathrm{C}}_2{\mathrm{H}}_6$
   

Calculate each of the following quantities in $2.00$ moles of ${\mathrm{H}}_3{\mathrm{PO}}_4$ :

1. moles of $\mathrm{H}$
   
2. moles of $\mathrm{O}$
   
3. atoms of $\mathrm{P}$
4. atoms of  $\mathrm{O}$
   

Calculate each of the following quantities in $0.185$ moles of ${\mathrm{C}}_6{\mathrm{H}}_{14}\mathrm{O}$ :

1. moles of  $\mathrm{C}$
   
2. moles of  $\mathrm{O}$
   
3. atoms of  $\mathrm{H}$
4. atoms of  $\mathrm{C}$

 Quinine, ${\mathrm{C}}_{20}{\mathrm{H}}_{24}{\mathrm{N}}_2{\mathrm{O}}_2$, is a component of tonic water and bitter lemon.
a. How many moles of $\mathrm{H}$ are in $1.5$ moles of quinine?
b. How many moles of $\mathrm{C}$ are in $5.0$ moles of quinine?
c. How many moles of $\mathrm{N}$ are in $0.020$ mole of quinine? 

Aluminum sulfate, ${\mathrm{Al}}_2{\left({\mathrm{SO}}_4\right)}_3$, is used in some antiperspirants.

1. How many moles of $\mathrm{O}$ are present in $3.0$ moles of ${\mathrm{Al}}_2{\left({\mathrm{SO}}_4\right)}_3$ ?
2.  How many moles of aluminum ions $\left({\mathrm{Al}}^{3+}\right)$ are present in $0.40$ mole of ${\mathrm{Al}}_2{\left({\mathrm{SO}}_4\right)}_3$ ?
3.  How many moles of sulfate ions $\left({{\mathrm{SO}}_4}^{2-}\right)$ are present in $1.5$ moles of ${\mathrm{Al}}_2{\left({\mathrm{SO}}_4\right)}_3$ ? 

Naproxen, found in Aleve, is used to treat the pain and inflammation caused by arthritis. Naproxen has a formula of ${\mathrm{C}}_{14}{\mathrm{H}}_{14}{\mathrm{O}}_3$.
a. How many moles of $\mathrm{C}$ are present in $2.30$ moles of naproxen?
b. How many moles of $\mathrm{H}$ are present in $0.444$ mole of naproxen?
c. How many moles of $\mathrm{O}$ are present in $0.0765$ mole of naproxen? 

Benadryl is an over-the-counter drug used to treat allergy symptoms. The formula of Benadryl is ${\mathrm{C}}_{17}{\mathrm{H}}_{21}\mathrm{NO}$.
a. How many moles of $\mathrm{C}$ are present in $0.733$ mole of Benadryl?
b. How many moles of $\mathrm{H}$ are present in $2.20$ moles of Benadryl?
c. How many moles of $\mathrm{N}$ are present in $1.54$ moles of Benadryl? 

Calculate the molar mass for each of the following : 

a. ${\mathrm{Cl}}_2$      b. ${\mathrm{C}}_3{\mathrm{H}}_6{\mathrm{O}}_3$     c. ${\mathrm{Mg}}_3{\left({\mathrm{PO}}_4\right)}_2$

Calculate the molar mass for each of the following : 

a. ${\mathrm{O}}_2$      b. ${\mathrm{KH}}_2{\mathrm{PO}}_4$     c. $\mathrm{Fe}{\left({\mathrm{ClO}}_4\right)}_3$

Calculate the molar mass for each of the following : 

a. ${\mathrm{AlF}}_3$      b. ${\mathrm{C}}_2{\mathrm{H}}_4{\mathrm{Cl}}_2$     c. ${\mathrm{SnF}}_2$

Calculate the molar mass for each of the following : 

a. ${\mathrm{C}}_4{\mathrm{H}}_8{\mathrm{O}}_4$      b. ${\mathrm{Ga}}_2{\left({\mathrm{CO}}_3\right)}_3$     c. ${\mathrm{KBrO}}_4$

Calculate the molar mass for each of the following:

a. $\mathrm{KCl}$, salt substitute

b. ${\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{NO}}_2$, niacin (vitamin $\mathrm{B}3$) needed for cell metabolism

c. ${\mathrm{C}}_{19}{\mathrm{H}}_{20}{\mathrm{FNO}}_3$, Paxil, antidepressant

Calculate the molar mass for each of the following:

a. ${\mathrm{FeSO}}_4$, iron supplement

b. ${\mathrm{Al}}_2{\mathrm{O}}_3$, absorbent and abrasive

c. ${\mathrm{C}}_7{\mathrm{H}}_5{\mathrm{NO}}_3\mathrm{S}$, saccharin, artificial sweetener

Calculate the molar mass for each of the following:

a. ${\mathrm{Al}}_2{\left({\mathrm{SO}}_4\right)}_3$ , antiperspirant

b. ${\mathrm{KC}}_4{\mathrm{H}}_5{\mathrm{O}}_6$, cream of tartar

C. ${\mathrm{C}}_{16}{\mathrm{H}}_{19}{\mathrm{N}}_3{\mathrm{O}}_5\mathrm{S}$, amoxicillin, antibiotic

Calculate the molar mass for each of the following:

a. ${\mathrm{C}}_8{\mathrm{H}}_9{\mathrm{NO}}_2$, acetaminophen used in Tylenol

b. ${\mathrm{Ca}}_3{\left({\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{O}}_7\right)}_2$, calcium supplement

c. ${\mathrm{C}}_{17}{\mathrm{H}}_{18}{\mathrm{FN}}_3{\mathrm{O}}_3$, Cipro, used to treat a range of bacterial infections

Calculate the molar mass for each of the following:

a. ${\mathrm{C}}_3{\mathrm{H}}_8\mathrm{O}$ , rubbing alcohol

b. ${\left({\mathrm{NH}}_4\right)}_{2}C{O}_3$ , baking powder

c. $\mathrm{Zn}{\left({\mathrm{C}}_2{\mathrm{H}}_3{\mathrm{O}}_2\right)}_2$, zinc supplement

Calculate the molar mass for each of the following:

a. ${\mathrm{CaSO}}_4$, calcium sulfate, used to make casts to protect broken bones

b. ${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{N}}_2{\mathrm{O}}_4\mathrm{Pt}$, Carboplatin, used in chemotherapy

c. ${\mathrm{C}}_{12}{\mathrm{H}}_{18}\mathrm{O}$, Propofol, used to induce anesthesia during surgery

 Calculate the mass, in grams, for each of the following:

 a.$1.50$ moles of $Na$ 

b. $2.80$ moles of $Ca$

c.$0.125$ mole of$C{O}_2$ 

d. $0.0485$mole of $N{a}_{2}C{O}_3$

e. $7.14 x {10}^2$moles of $PC{I}_3$

Calculate the mass, in grams, for each of the following: 

a. $5.12$ moles of $Al$

b .$0.75$ mole of$Cu$

c. $3.52$ moles of $MgB{r}_2$

d. $0.145$ mole of $C_2{H}_{6}O$

e. $2.08$moles of ${\left(NH4\right)}_{2}S{O}_4$

a. The compound ${\mathrm{MgSO}}_4$, Epsom salts, is used to soothe sore feet and muscles. How many grams will you need to prepare a bath containing $5.00$ mole of Epsom salts?

b. Potassium iodide, $\mathrm{KI}$, is used as an expectorant. How many grams are in $0.450$ mole of potassium iodide?

Calculate the mass, in grams, in  $0.150$ mole of each of the following: 

a. $Ne$

b.$I_2$

 c. $N{a}_{2}O$

d. $Ca{\left(N{O}_3\right)}_2$

 e. $C_6{H}_{14}$

Calculate the mass, in grams, in $2.28$ moles of each of the following: 

a. $N_2$

b. $S{O}_3$

c.$C_3{H}_6{O}_3$

d. $Mg{\left(HC{O}_3\right)}_2$

 e. $S{F}_6$

Calculate the number of moles in each of the following: 

a. $85.2$ g of $Ni$ 

b. $144$g of $K$

 c. $6.4$g of $H_{2}O$

d. $308$g of$BaS{O}_4$

e. $252.8$g of fructose, $C_6{H}_{12}{O}_6$

Calculate the number of moles in $25.0$g of each of the following: 

a. $He$

b. $O$

c. $Al{\left(OH\right)}_3$

d. $G{a}_2{S}_3$

e. $C_4{H}_{10}$, butane 

Calculate the number of moles in $4.0$ g of each of the following:

a. $Au$ 

b. $Sn{O}_2$

c. $C{S}_2$ 

d. $C{a}_3 N_2$

e. $C_6{H}_8{O}_6$, vitamin C 

Chloroethane,$C_2{H}_{5}CI,$ is used to diagnose dead tooth nerves.

 a. How many moles are in $34.0$ g of chloroethane?

 b. How many grams are in$1.50$ moles of chloroethane? 

Allyl sulfide, ${\left(C_3{H}_5\right)}_{2}S$, gives garlic, onions, and leeks their characteristic odor. The characteristic odor of garlic is due to a sulfur-containing compound. 

a. How many moles are in $23.2$g of allyl sulfide? 

b. How many grams are in $0.75$ mole of allyl sulfide? 

Calculate the number of moles in each of the following: 

a.$82.0$g of $Ag$

b . $0.288$g of $C$

c. $15.0$g of ammonia, $N{H}_3$

d. $7.25$ g of $C{H}_4$

 e. $245$g of$F{e}_2{O}_3$; 

a. Cyclopropane, ${\mathrm{C}}_3{\mathrm{H}}_6$, is an anesthetic given by inhalation. How many grams are in $0.25$ mole of cyclopropane?

b. The sedative Demerol hydrochloride has the formula $C_{15}{H}_{22}CIN{O}_2$. How many grams are in $0.025$ mole of Demerol hydrochloride?

Dinitrogen oxide (or nitrous oxide), ${\mathrm{N}}_2\mathrm{O}$, also known as laughing gas, is widely used as an anesthetic in dentistry. 

a. How many grams are in style="max-width: none; vertical-align: -4px;" $1.50$ moles of dinitrogen oxide? 

b. How many moles are in $34.0$ g of dinitrogen oxide?

Chloroform, ${\mathrm{CHCl}}_3$, was formerly used as an anesthetic but its use was discontinued due to respiratory and cardiac failure. 

a. How many grams are in $0.122$ mole of chloroform?

b. How many moles are in $26.7$ g of chloroform?

Propane gas, ${\mathrm{C}}_3{\mathrm{H}}_8$, undergoes combustion with oxygen gas to produce carbon dioxide and water gases. Propane has a density of $2.02 g/L$ at room temperature. ($7.4, 7.8$)

a. Write the balanced chemical equation.

b. How many grams of ${\mathrm{H}}_2\mathrm{O}$ form when $5.00 L$ of ${\mathrm{C}}_3{\mathrm{H}}_8$ reacts?

c. How many grams of ${\mathrm{H}}_2\mathrm{O}$ can be produced from the reaction of $100 g$ of ${\mathrm{C}}_3{\mathrm{H}}_8$?

Determine whether each of the following is balanced or not balanced:

a. $\mathrm{S}\left(\mathrm{s}\right) + {\mathrm{O}}_2\left(\mathrm{g}\right) \to {\mathrm{SO}}_3\left(\mathrm{g}\right)$

b. $2\mathrm{Ga}\left(\mathrm{s}\right) + 3{\mathrm{Cl}}_2\left(\mathrm{g}\right) \to 2{\mathrm{GaCl}}_3\left(\mathrm{s}\right)$

c. ${\mathrm{H}}_2\left(\mathrm{g}\right) + {\mathrm{O}}_2\left(\mathrm{g}\right)\to {\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)$

d. ${\mathrm{C}}_3{\mathrm{H}}_8\left(\mathrm{g}\right) + 5{\mathrm{O}}_2\left(\mathrm{g}\right) \stackrel{∆}{\to }3{\mathrm{CO}}_2\left(\mathrm{g}\right) +4{\mathrm{H}}_2\mathrm{O}$

Determine whether each of the following chemical equations are balanced or not balanced:

a. $PC{l}_3\left(s\right) + C{l}_2\left(g\right) \to PC{l}_5\left(s\right)$

b. $CO\left(g\right) + 2H_2\left(g\right)\to C{H}_{4}O\left(g\right)$

c. $2KCl{O}_3\left(s\right)\to 2KCl\left(s\right) + O_2\left(g\right)$

d. $Mg\left(s\right) + N_2\left(g\right)\to M{g}_3{N}_2\left(s\right)$

Balance each of the following chemical equations:

$$\begin{gathered} \text{ a. }{\mathrm{N}}_2\left(g\right)+{\mathrm{O}}_2\left(g\right)⟶\mathrm{NO}\left(g\right) \\ \text{ b. }\mathrm{HgO}\left(s\right)⟶\mathrm{Hg}\left(l\right)+{\mathrm{O}}_2\left(g\right) \\ \text{ c. }\mathrm{Fe}\left(s\right)+{\mathrm{O}}_2\left(g\right)⟶{\mathrm{Fe}}_2{\mathrm{O}}_3\left(s\right) \\ \text{ d. }\mathrm{Na}\left(s\right)+{\mathrm{Cl}}_2\left(g\right)⟶\mathrm{NaCl}\left(s\right) \end{gathered}$$

Balance each of the following chemical equations:

$$\begin{gathered} \text{ a. }\mathrm{Ca}\left(s\right)+{\mathrm{Br}}_2\left(l\right)⟶{\mathrm{CaBr}}_2\left(s\right) \\ \text{ b. }{\mathrm{P}}_4\left(s\right)+{\mathrm{O}}_2\left(g\right)⟶{\mathrm{P}}_4{\mathrm{O}}_{10}\left(s\right) \\ \text{ c. }{\mathrm{Sb}}_2{ \mathrm{S}}_3\left(s\right)+\mathrm{HCl}\left(aq\right)⟶{\mathrm{SbCl}}_3\left(aq\right)+{\mathrm{H}}_2 \mathrm{S}\left(g\right) \\ \text{ d. }{\mathrm{Fe}}_2{\mathrm{O}}_3\left(s\right)+\mathrm{C}\left(s\right)⟶\mathrm{Fe}\left(s\right)+\mathrm{CO}\left(g\right) \end{gathered}$$

Balance each of the following chemical equations:

$\text{ a. }\mathrm{Mg}\left(s\right)+{\mathrm{AgNO}}_3\left(aq\right)⟶\mathrm{Mg}{\left({\mathrm{NO}}_3\right)}_2\left(aq\right)+\mathrm{Ag}\left(s\right)$

$\text{ b. }\mathrm{Al}\left(s\right)+{\mathrm{CuSO}}_4\left(aq\right)⟶{\mathrm{Al}}_2{\left({\mathrm{SO}}_4\right)}_3\left(aq\right)+\mathrm{Cu}\left(s\right)$
$\text{ c. }\mathrm{Pb}{\left({\mathrm{NO}}_3\right)}_2\left(aq\right)+\mathrm{NaCl}\left(aq\right)⟶{\mathrm{PbCl}}_2\left(s\right)+{\mathrm{NaNO}}_3(aq$

$\text{ d. }\mathrm{Al}\left(s\right)+\mathrm{HCl}\left(aq\right)⟶{\mathrm{H}}_2\left(g\right)+{\mathrm{AlCl}}_3\left(aq\right)$

Balance each of the following chemical equations:

$$\begin{gathered} \text{ a. }\mathrm{Zn}\left(s\right)+{\mathrm{HNO}}_3\left(aq\right)⟶{\mathrm{H}}_2\left(g\right)+\mathrm{Zn}{\left({\mathrm{NO}}_3\right)}_2\left(aq\right) \\ \text{ b. }\mathrm{Al}\left(s\right)+{\mathrm{H}}_2{\mathrm{SO}}_4\left(aq\right)⟶{\mathrm{H}}_2\left(g\right)+{\mathrm{Al}}_2{\left({\mathrm{SO}}_4\right)}_3\left(aq\right) \\ \text{ c. }{\mathrm{K}}_2{\mathrm{SO}}_4\left(aq\right)+{\mathrm{BaCl}}_2\left(aq\right)⟶{\mathrm{BaSO}}_4\left(s\right)+\mathrm{KCl}\left(aq\right) \\ \text{ d. }{\mathrm{CaCO}}_3\left(s\right)⟶\mathrm{CaO}\left(s\right)+{\mathrm{CO}}_2\left(g\right) \end{gathered}$$

Classify each of the following as a combination, decomposition, single replacement, double replacement, or combustion reaction: 

a. $2{\mathrm{Al}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)\stackrel{∆}{\to } 4\mathrm{Al}\left(\mathrm{s}\right) +3{\mathrm{O}}_2\left(\mathrm{g}\right)$

b. ${\mathrm{Br}}_2\left(\mathrm{l}\right)+{\mathrm{BaI}}_2\left(\mathrm{s}\right)\to {\mathrm{BaBr}}_2\left(\mathrm{s}\right)+{\mathrm{I}}_2\left(\mathrm{s}\right)$

c. $2{\mathrm{C}}_2{\mathrm{H}}_2\left(\mathrm{g}\right)+5{\mathrm{O}}_2\left(\mathrm{g}\right)\stackrel{∆}{\to }4{\mathrm{CO}}_2\left(\mathrm{g}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)$ 

d.  ${\mathrm{BaCl}}_2\left(\mathrm{aq}\right)+{\mathrm{K}}_2{\mathrm{CO}}_3\left(\mathrm{aq}\right)\to {\mathrm{BaCO}}_3\left(\mathrm{s}\right)+\mathrm{KCl}\left(\mathrm{aq}\right)$

e. $\mathrm{Pb}\left(\mathrm{s}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\to {\mathrm{PbO}}_2\left(\mathrm{s}\right)$

Classify each of the following as a combination, decomposition, single replacement, double replacement, or combustion reaction: 

a. $H_{\mathit{2}}\left(g\right)+B{r}_{\mathit{2}}\left(l\right)\to 2HBr\left(\mathrm{g}\right)$

b. ${\mathrm{AgNO}}_3\left(\mathrm{aq}\right) + \mathrm{NaCl}\left(\mathrm{aq}\right) \to \mathrm{AgCl}\left(\mathrm{s}\right) + {\mathrm{NaNO}}_3\left(\mathrm{aq}\right)$ 

c. $2{\mathrm{H}}_2{\mathrm{O}}_2\left(\mathrm{aq}\right) \to 2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) + {\mathrm{O}}_2\left(\mathrm{g}\right)$

d. $\mathrm{Zn}\left(\mathrm{s}\right) + {\mathrm{CuCl}}_2\left(\mathrm{aq}\right) \to \mathrm{Cu}\left(\mathrm{s}\right) + {\mathrm{ZnCl}}_2\left(\mathrm{aq}\right)$

e.${\mathrm{C}}_5{\mathrm{H}}_8\left(\mathrm{g}\right) + {70}_2\left(\mathrm{g}\right) \to 5{\mathrm{CO}}_2\left(\mathrm{g}\right) + 4{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)$

Classify each of the following as a combination, decomposition, single replacement, double replacement, or combustion reaction: 

a. $4\mathrm{Fe}\left(\mathrm{s}\right) + 3{\mathrm{O}}_2\left(\mathrm{g}\right) \to 2{\mathrm{Fe}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)$

b. $\mathrm{Mg}\left(\mathrm{s}\right) + 2{\mathrm{AgNO}}_3\left(\mathrm{aq}\right) \to 2\mathrm{Ag}\left(\mathrm{s}\right) + \mathrm{Mg}{\left({\mathrm{NO}}_3\right)}_2\left(\mathrm{aq}\right)$

c. ${\mathrm{CuCO}}_3\left(\mathrm{s}\right) \to \mathrm{CuO}\left(\mathrm{s}\right) + {\mathrm{CO}}_2\left(\mathrm{g}\right)$

d. ${\mathrm{Al}}_2{\left({\mathrm{SO}}_4\right)}_3\left(\mathrm{aq}\right) + 6\mathrm{KOH}\left(\mathrm{aq}\right) \to 2\mathrm{Al}{\left(\mathrm{OH}\right)}_3\left(\mathrm{s}\right) + 3{\mathrm{K}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)$ 

e. ${\mathrm{C}}_4{\mathrm{H}}_8\left(\mathrm{g}\right) + 6{\mathrm{O}}_2\left(\mathrm{g}\right) \to 4{\mathrm{CO}}_2\left(\mathrm{g}\right) + 4{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)$

Classify each of the following as a combination, decomposition, single replacement, double replacement, or combustion reaction: 

a. $\mathrm{CuO}\left(\mathrm{s}\right) + 2\mathrm{HCl}\left(\mathrm{aq}\right) \to {\mathrm{CuCl}}_2\left(\mathrm{aq}\right) + {\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

b. $2\mathrm{Al}\left(\mathrm{s}\right) + 3{\mathrm{Br}}_2\left(\mathrm{l}\right) \to 2{\mathrm{AlBr}}_3\left(\mathrm{s}\right)$

c. $2{\mathrm{C}}_2{\mathrm{H}}_2\left(\mathrm{g}\right) + 5{\mathrm{O}}_2\left(\mathrm{g}\right) \to 4{\mathrm{CO}}_2\left(\mathrm{g}\right) + 2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)$

d. ${\mathrm{Fe}}_2{\mathrm{O}}_3\left(\mathrm{s}\right) + 3\mathrm{C}\left(\mathrm{s}\right)\to 2\mathrm{Fe}\left(\mathrm{s}\right) + 3\mathrm{CO}\left(\mathrm{g}\right)$

e. ${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6\left(\mathrm{aq}\right) \to 2{\mathrm{C}}_2{\mathrm{H}}_6\mathrm{O}\left(\mathrm{aq}\right) + 2{\mathrm{CO}}_2\left(\mathrm{g}\right)$

Identify each of the following as an oxidation or a reduction: 

a. ${\mathrm{Na}}^{+}\left(\mathrm{aq}\right) +{\mathrm{e}}^{-}\to 2 \mathrm{Na}\left(\mathrm{s}\right)$

b. $\mathrm{Ni}\left(\mathrm{s}\right)\to {\mathrm{Ni}}^{2+}\left(\mathrm{aq}\right) + 2{\mathrm{e}}^{-}$

c. ${\mathrm{Cr}}^{3+}\left(\mathrm{aq}\right) + 3{\mathrm{e}}^{-}\to \mathrm{Cr}\left(\mathrm{s}\right)$

d. $2{\mathrm{H}}^{+}\left(\mathrm{aq}\right) + 2{\mathrm{e}}^{-}\to {\mathrm{H}}_2\left(\mathrm{g}\right)$

Identify each of the following as an oxidation or a reduction: 

a. ${\mathrm{O}}_2\left(\mathrm{g}\right) + 4{\mathrm{e}}^{-}\to 2{\mathrm{O}}^{2-} \left(\mathrm{aq}\right)$

b. $\mathrm{Ag}\left(\mathrm{s}\right) \to {\mathrm{Ag}}^{+}\left(\mathrm{aq}\right) +{\mathrm{e}}^{-}$

c. ${\mathrm{Fe}}^{3+}\left(\mathrm{aq}\right) +{\mathrm{e}}^{-}\to {\mathrm{Fe}}^{2+} \left(\mathrm{aq}\right)$

d. $2\mathrm{Br}{ }^{-}\left(\mathrm{aq}\right) \to \mathrm{Br}2\left(\mathrm{l}\right) + 2 {\mathrm{e}}^{-}$

In the mitochondria of human cells, energy is provided by the oxidation and reduction reactions of the iron ions in the cytochromes in electron transport. Identify each of the following as an oxidation or a reduction: 

a. ${\mathrm{Fe}}^{3+} + {\mathrm{e}}^{-} \to {\mathrm{Fe}}^{2+}$

b. ${\mathrm{Fe}}^{2+} \to {\mathrm{Fe}}^{3+} + {\mathrm{e}}^{-}$

Chlorine $\left(C{l}_2\right)$ is a strong germicide used to disinfect drinking water and to kill microbes in swimming pools. If the product is $C{l}^{-}$, was the elemental chlorine oxidized or reduced?