6: Homework Solutions

Last updated
Save as PDF

Page ID: 43940

\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \) \( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)\(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\) \(\newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\) \( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\) \( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\) \( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\) \( \newcommand{\Span}{\mathrm{span}}\)\(\newcommand{\AA}{\unicode[.8,0]{x212B}}\)

Molecular Mass, Formula Mass, and Molar Mass

(1) 1 mole = 6.02 x 10²³

(2) What is the mass of each of the following quantities:

2.0 g
36 g
21 g
18 g
12 g

(3) Chlorine atoms because they contain more protons and neutrons.

(4) 32.05 amu/molecule; 32.05 g/mole

(5) For each of these different compounds, using the given masses, calculate how many moles each sample contains.

0.053 mole NaCl
0.14 mole H₂O₂
0.3 mole LiOH
0.33 mole O₂
1.3 mole NH₃

(6) Contrasting with the previous problem, this time find the mass of each sample by using the given number of moles.

190 g P
220 g Fe
198 g F₂
47 g HCl
160 g Ne

(7) Combine the following ions into an ionic compound and calculate the molar mass.

(NH₄)₂S; 68.16 g/mol
Sr₃N₂; 290.88 g/mol
AlF₃; 83.98 g/mol
CaI₂; 293.88 g/mol
Ag₂O; 231.74 g/mol

Mole Questions

(8) 84.01 g/mol

(9) 0.50 mol NaHCO₃

(10) 35 g NaHCO₃

(11) 1.8 x 10²³ formula units of NaHCO₃

(12) 2.3 x 10²² Na⁺ ions

(13) 92.11 g/mol

(14) 0.46 mole glycerine

(15) 39 g glycerine

(16) 1.6 x 10²³ molecules glycerine

(17) 6.3 x 10²² C atoms

(18) a) 194.22 g/mol caffeine and 163.94 g/mol for sodium phosphate

b) Caffeine is covalent because all the atoms are non-metals. Sodium phosphate is ionic because it contains a metal cation and polyatomic anion.

c) sodium phosphate because 0.014 mol sodium phosphate is greater than 0.012 mol caffeine

(19) CH₂O because it has the smallest molar mass.

(20) a) NaHCO₃

b) NaHCO₃

Writing and Balancing a Chemical Equation

(21) Balance the following chemical equations.

\(2 Al_{(s)} + 6 H_2O_{(l)} \rightarrow 2 AlOH_{(aq)} + 3 H_{2\;(g)}\)
\(N_{2\;(g)} + 2 O_{2\; (g)} \rightarrow 2 NO_{2\; (g)}\)
\(H_2CO_{3\;(aq)} \rightarrow H_2O_{(l)} + CO_{2\; (g)}\)
\(2 P_2O_{5\;(s)} \rightarrow P_{4\;(s)} + 5 O_{2\; (g)}\)
\(N_{2\;(g)} + 4 H_{2\;(g)} + Cl_{2\;(g)} \rightarrow 2 NH_4Cl_{(s)}\)

(22) Balance each of the given combustion reactions.

\(2 C_6H_6(l) + 15 O_{2\; (g)} \rightarrow 12 CO_{2\; (g)} + 6 H_2O_{(g)}\)
\(2 C_2H_2(g) + 5 O_{2\; (g)} \rightarrow 4 CO_{2\; (g)} + 2 H_2O_{(g)}\)
\(2 C_8H_{18}(l) + 25 O_{2\; (g)} \rightarrow 16 CO_{2\; (g)} + 18 H_2O_{(g)}\)
\(C_4H_9OH(l) + 6 O_{2\; (g)} \rightarrow 4 CO_{2\; (g)} + 5 H_2O_{(g)}\)
2 CH₃(CH₂)₄OCH₂CH₃(l) + 21 O₂(g) → 14 CO₂(g) + 16 H₂O(g)

(23) The next set of chemical equations are NOT properly balanced. Alter the coefficients as needed so that the equations are properly balanced.

\(N_{2\;(g)} + 3 H_{2\;(g)} \rightarrow 2NH_{3\;(l)} \)
\(Ba(OH)_2\;{(aq)} + H_2SO_{4\;(aq)} \rightarrow BaSO_{4\;(aq)} + 2 H_2O(l) \)
\(CH_{4\; (g)} + N_{2\;(g)} \rightarrow 2 HCN(g) + H_{2\;(g)} \)
\(4 Cl_{2\;(g)} + 4 H_2O(l) \rightarrow HClO_{4\;(aq)} + 7 HCl(aq) \)
\(PH_3(aq) + 2O_{2\; (g)} \rightarrow H_3PO_{4\;(aq)} \)

Energy and Chemical Reactions

(24)

54 kcal; 2.3 x 10⁵ J
36 kcal; 1.5 x 10⁵ J
28 kcal; 1.2 x 10⁵ J
104 kcal; 4.3 x 10⁵ J
128 kcal; 5.4 x 10⁵ J

(25)

exothermic
endothermic
exothermic
exothermic
endothermic

(26) Perform the following unit conversions.

4.1 x 10^-3 kcal
1.9 x 10³cal
3.77 x 10³ J
837 kJ
1.3 kcal

(27) Proteins and carbohydrates both contain 4 Cal per gram. Fats contain the most energy at 9 Cal per gram.

(28) For each of the following characteristics, determine whether they are more common of anabolic reactions or catabolic reactions.

catabolic
anabolic
anabolic
catabolic

(29) catabolic

Kinetics: Reaction Rates

(30)

(31)

exothermic because the products are lower in energy than the reactants.
refer to graph
refer to graph
refer to graph
refer to graph
The transition state and activation energy decrease when a catalyst is added. The energy of the reactants, products, and enthalpy remain the same.

(32) Many things can affect the rate of a reaction. Determine what effect the following scenarios may have on a reaction.

increases the reaction rate
increases the reaction rate
decreases the reaction rate
decreases the reaction rate
increases the reaction rate

(33) Answer the following true or false statements.

False
False
False
True
True

(34)

Equilibrium & Le Châtelier’s Principle

(35)

equilibrium
right
left
right
left
left
right

(36)

\( CO_{(g)} + 2H_{2\; (g)} \rightleftharpoons CH_3OH_{(g)}\)
right
left
right
left

Additional Exercises

(37) 480 kcal

(38) Protein: 700 kcal & 175 g; Carbohydrates: 900 kcal & 225 g; Fat: 400 kcal or 44 g

(39)

endothermic
exothermic
the glass feels colder because the heat moves into the iodine crystals as they sublimate.

(40) C₃H₈ + 5 O₂ → 3 CO₂ + 4 H₂O + HEAT

(41) 2300 mol of water

(42) 0.0187 mol Fe

(43)

2.67 mol of Ca²⁺ and 5.34 mol of Cl^-
5.34 mol of Na⁺, 2.67 mol of SO₄²^-
2.67 mol of Al³⁺, 8.01 mol of NO₃^-
8.01 mol of Fe²⁺, and 5.34 mol of PO₄³^-

(44) a) 0.00445 mol C and 0.178 mol H

b) 0.0045 mol C and 0.00890 mol O

c) 0.134 mol C and 0.0356 mol H

d) 0.00890 mol N and 0.0223 mol O

(45) 324 g/mol

(46) 5.3 x 10^-7 mol hemoglobin