Problems: Choose the best answer.
Hints: 1 g of water = 1mL
Cp of water is 4.18 J/ g* oC
STP = 0 oC and 101.3 kPa
K = 273 + oC
All chemical reactions given are unbalanced
r= 8.31 kPa*L/mol*k
r = .0821 L*atm/ mol*k
1) What quantity of heat is required to raise 6 g of water from 50 oC to 100 oC?
6 x 50 x 4.184 = 1255.2 J
2) What quantity of ice, can be melted from 10 oC to 0 oC using 6.8 x 10 4 J?
6.8 x 10 4 / 10/ 4.184 = 1625 g
3) Calculate the heat of reaction for the following:
Cu2S(s) + 2S(s) ---- 2 CuS
Heat of formation values: -79.5 kj/mol , 0 j/mol, -53.1 kj/mol respectively
2(-53.1) – [ -79.5 + 2(0)] = - 26.7 kJ
4) Is the above reactions endothermic or exothermic?
Exothermic
5) Would the reaction of solid calcium carbonate breaking down into solid calcium oxide
and carbon dioxide gas be spontaneous?
Yes, because you are going to more disorder
6) What volume will 18.0 g of nitrogen monoxide occupy at STP, assuming it acts like an
ideal gas.
18.0 g / 30.01 = .60 mols x 22.4 L/mol = 13.4 L
7) At constant pressure, the volume of a gas is increased from 150 L to 300 L by heating
it. If the original temperature of the gas was 20 oC, what will its final temperature be?
Use V1T2 = V2T1
(150 L) T2 = (300L)(393K)
thus 786 K or 513 oC
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8) When measured at 25 C and 93.3 kPa, a quantity of gas has a volume of 500 L. What
volume will it occupy at STP?
Use P1V1T2 = P2V2T1
V2 = (93.3 kPa)(500L)(273K)/ (101.3 kPa)/(298K) = 422 L
9) A solution of calcium hydroxide contains 19.2 g of solute in 160 mL of solution. What is
the molarity of this solution?
19.2g/ 74g = .259mols/ .160L = 1.62 M
10) How many grams of sulfuric acid are present in 62.2 mL of 4.54 M solution?
.0622 L x 4.54 M = .282 mols x 98 g = 27.6 g
11) What is the molality of a solution containing 45.8 g of sodium chloride in 456 g of water?
45.8 g / 58.33 g = .785 mols/ .456 kg = 1.72 m
Use the following unbalanced reaction to answer the questions
Cu(s) +
4HNO3(aq) -----
Cu(NO3)2 (aq) + 2NO2(g)
+ 2 H2O(l)
12) How many grams of copper II nitrate can be made from 5.77 mols of copper?
5.77 mols x 1mol/1mol x 188/1 = 1085 g
13) How many grams of copper are needed to produce 90.0 g of water?
90.0 g/ 18.02 g = 4.99 mols x 1mol/2mols x 64g/1mol = 160 g
14) How many liters of nitrogen dioxide can be made from 23.4 g of nitric acid at STP?
23.4 g/ 63 g = .371 mols x 2mols/4mols x 22.4L/1mol = 4.16 L
15) How many grams of water can be produced from 30.0 g of copper and 30.0 g of nitric acid?
30.0g / 64g = .469 mols x 1mol/2mols x 18.02g/1mol = 4.23 g
30.0 g/ 63 g = .476 mols x 2 mol/ 4mols x 18.02 g/ 1 mol = 4.29 g
Thus 4.23 g is the answer
16) How many grams of lithium nitrate will be produced given .30M solution of magnesium
nitrate in a 500 mL container?
2 Li(s) + Mg(NO3)2(aq) ----- 2 LiNO3(aq) + Mg(s)
(.500L) (.30M) = .15mols x 2mols/1mol x 69g/1 mol = 20.7 g
Use the following reaction to answer the following questions:
P4(g) + 6 H2(g) ---- 4 PH3(g)
+ Heat
17) What shift would occur if the concentration of hydrogen gas was decreased?
a) right
b) left
c) remain the same
18) What shift would occur if the pressure was increased?
a) right
b) left
c) remain the same
19) What shift would occur if the temperature was increased?
a) right
b) left
c) remain the same
20) NH3 + H2O --- NH4+
+ OHWho is the conjugate acid for the forward reaction?
a) NH3
c) NH4+
b) H2O
d) OH21) What is the pH of a 2.93 x 10 -1 M solution of Hydrochloric acid?
pH = -log (2.93 x 10 -1 M) = .533
22) What is the hydroxide concentration of solution with a pH of 4.56?
14 – 4.56 = 9.44 pOH
[OH-] = antilog (-9.44) = 3.63 x 10 -10 M
23) What is the hydronium concentration of an acid with a pH of 4.78?
[H3O+] = antilog ( - 4.78) = 1.65 x 10 -5 M
24) What is the pH of sodium hydroxide, given the concentration is 1.39 x 10
pOH = - log ( 1.39 x 10 -4 M) =3.86 pH = 14 – 3.86 = 10.1
Concepts:
1) According to the kinetic molecular theory all particles move.
-4
M?
2) Which state of matter has the greatest density? solid Which has the least? gas
3) Which state of matter has the most space between its particles? gas
4) What is the difference between diffusion and effusion? Effusion occurs through a tiny opening while diffusion is the spreading
out of gas
5) What are the three intermolecular forces? Hydrogen bonding, London dispersion forces, dipole to dipole
6) What are the three intramolecular forces? Ionic, covalent and metallic
7) Which form of matter has the strongest intermolecular forces? Solid The weakest? Gas
8) What is the difference between evaporation and boiling? Evaporation is a liquid to a gas and occurs at any temperature and
begins at the surface, while boiling occurs when atmospheric pressure equals vapor pressure of the liquid
9) When will a liquid boil? When atmospheric pressure equals the vapor pressure of the liquid
10) What is needed for a spontaneous reaction? An exothermic reaction and disorder is increasing
12) What type of state of matter has the most entropy? Gas
13) What do you need to do to make a reaction spontaneous if the reaction is endothermic and the disorder is increasing?
Increase of temperature
14)Electrolytes can carry electrons (electricity)
15) What is the difference between a homogeneous and heterogeneous mixture? Homogeneous
mixture is the same throughout, you cannot tell the different parts that make it up and these
mixtures are called solutions, while heterogeneous is not the same and you can tell the different
parts, these are called colloids or suspensions.
16) What factors can affect solubility? Nature of the solute and solvent (remember “like
dissolves like”), temperature, and pressure (if it is a gas)
17) What factors can affect the rate of dissolution? Temperature, surface area, agitation
(stirring), amount of solute already dissolved
18) What makes a property a colligative property? A physical property of a solution that has to
do with the concentration of the solute dissolved rather than its identity- boiling point elevation,
freezing point depression, vapor pressure lowering, and osmotic pressure.
19) What is an Arrhenius acid and base? An acid ionizes into an H+ while a base dissociates into
an OH 20) What is a Bronsted-Lowry acid and base? An acid will donate a proton (H+) while a base will
accept a proton ( H+)
21) What determines the strength of an acid? The amount that will ionize – 100% ionization is
strong , HCl, HNO3 and H2SO4 are strong acids
22) What is needed for an effective collision? The right amount of speed and orientation
23) What factors can help increase reaction rate? Increase temperature, pressure,
concentration and surface area. Reaction rate can also depend upon the nature of the
reactants.
24) What is activation energy? The amount of energy needed to start a chemical reaction. What
is an activated complex? The temporary and unstable product created during one of the steps
involved in the reaction
25)What is the effect of a catalyst on a reaction? The catalyst will lower the activation energy,
but will not affect the product. Catalyst target the slowest step in a chemical reaction called the
rate determining step.
26) Why do we balance chemical reactions? The Law of Conservation of Matter states that
matter cannot be created or destroyed.
27) What does the limiting reactant do? This is the reactant that is completely used up and
determines how much product can be made. What do you call the maximum amount of product
a reaction can make? The theoretical yield
28) What type of reaction can form both products and then re-form the reactants? A reversible
reaction which is symbolized by a double arrow. The forward reaction is to the right while the
reverse reaction is to the left.
29) What happens at equilibrium? The rate of the forward reaction is equal to the rate of the
reverse reaction. This can be calculated by dividing the concentrations of the products by the
concentrations of the reactants.
30) How do you know a reaction has run to completion? Usually when a solid or a pure
substance is formed. What type of reaction will most likely not be a reversible reaction? A
double replacement reaction that produces a precipitate or any reaction in which a pure
substance is created (like water) or a single replacement reaction where hydrogen gas (which
can escape) is produced (acid + metal)