Spring 2012 CHM2045 Exam 1

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GENERAL CHEMISTRY 1

CHM2045

Exam 1 - Chapters 1-4 & 6

Spring 2012

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2

Dimensional Analysis

Dimensional analysis uses units to find an answer. To solve these problems use the

following guideline:

Decide the starting point- rarely ever start with density

Use units to solve, canceling out as you go

Check that your answer makes sense

Temperature To convert from Celsius to Kelvin use the following formula:

273.15oT in K T in C

Significant Figures and Scientific Notation

Values are rewritten to avoid writing large numbers, in scientific notation:

Ex. 0.0000420 becomes 4.20 x 10-5.

To work out how many sig. figs. a value has don’t count the zeros before any other

numbers, but do count the zeros after.

Ex. 0.00820 has 3 sig. figs. and is correctly written as 8.20 x 10-3.

Mnemonic Prefix Abbreviation Meaning Example

The Tera- T 1012 1 Tm = 1 x 1012 m

Great Giga- G 109 1 Gm = 1 x 109 m

Monarch Mega- M 106 1 Mm = 1 x 106 m

King Kilo- K 103 1 km = 1 x 103 m

Henry Hecto- H 102 1 Hm = 1 x 102 m

Died Deca- D 101 1 Dm = 1 x 101 m

By Base Unit m, g or L 100 1 m = 1.0 m

Drinking Deci- d 10-1 1 dm = 1 x 10-1 m

Chocolate Centi- c 10-2 1 cm = 1 x 10-2 m

Milk Milli- m 10-3 1 mm = 1 x 10-3 m

Monday Micro- 10-6 1 m = 1 x 10-6 m

Night Nano- n 10-9 1 nm = 1 x 10-9 m

Past Pico- p 10-12 1 pm = 1 x 10-12 m


3

Problem 1:

You’re driving to Tallahassee to watch the Gator’s kick some Seminole-behind with 12.0 gallons

of gas. If your Hummer gets 11,710 meters/gallon how far will you make it? (2.54 cm = 1 inch)

a) 87.3 miles b) 47.8 miles c) 127 miles d) 32 miles e) 576 miles

Elements

The atom is composed of a central core nucleus that is surrounded by electrons.

The nucleus:

¤ contains protons (which have a positive charge).

¤ contains neutrons (which have no charge).

Electrons have a negative charge.

Atoms have the same number of protons and electrons.

If two atoms have a different amount of electrons they are ions

If two atoms have a different number of neutrons they are isotopes

If two atoms have different numbers of protons well… they’re different elements

Protons and neutrons have about the same mass 1 amu and electrons have relatively no

mass (about 0.00055 amu)

The mass number of an atom essentially comes from adding the number of protons and

neutrons in the nucleus

XM

Z

X is the element, M is the mass number, and Z is the atomic number.


4

Isotopes

If isotopes have different numbers of neutrons then they also have a different mass.

Relative abundance is the percentage theat exists in nature. The sum of all isotope

abundances has to equal 100%.

To find isotope mass solve for x in the equation below when necessary information is given:

st ndAvg. Atomic Mass = 1 Isotope Mass Rel. Abundance + 2 Isotope Mass Rel. Abundance ...

Problem 2:

Chlorine consists of three common isotopes. One isotope has an atomic mass of 34.9amu and is

20% abundant, another has an atomic mass of 35.2 and the last has an atomic mass of 35.8amu.

What is the percent abundance of the heaviest isotope?

a) 45.7 % b) 82.4 % c) 51.7 % d) 28.3 % e) 4.20%

Bonding

When two elements join together they can form an ionic or covalent bond.

If a metal and a nonmetal come together, they form an ionic bond.

¤ -one atom gets a positive charge (ca+ion), the other a negative charge (anion).

¤ -To name this compound name the metal and the ‚ide‛ of the nonmetal

ex: NaBr is Sodium Bromide

¤ Polyatomic ions also form ionic bonds but you name them ‚as-is.‛ Do not add ide.

If two nonmetals come together they form a covalent bond by sharing electrons.

¤ To name this compound, use prefixes- mono, di, tri, tetra, penta, hexa, hepta, octa,

nona, deca and ‚ide‛

ex: N2O5 is dinitrogen pentoxide


5

If hydrogen joins with a nonmetal or polyatomic ion an acid is formed

¤ If the acid is HX where X is a halogen, then the acid is named hydro_______ic acid

Ex: HCl is hydrochloric acid

¤ If naming an acid of a polyatomic molecule use this pneumonic- Ric Ate (o)Us Rite?

Which means use ‚ric‛ if the compound is an ‚ate‛ and use ‚ous‛ if the compound

is an ‚ite‛

Ex: H2SO3 is sulfurous acid

Polyatomic Ions + 2- 3-

4 4 4

- 2-

3

ammonium NH sulfate SO phosphate PO

hydroxide OH sulfite SO 3-

3

- 2-

3 3

- 2-

4 2

-

phosphite PO

acetate CH COO carbonate CO

permanganate MnO carbonite CO

cyanide CN chromate 2-

4

2-

3 2 7

2

-

3

-

2

CrO

chlorate ClO dichromate Cr O

chlorite ClO

nitrate NO

nitrite NO

Periodic Table Notes Group 1a = alkali metals

Groups 2a = alkaline earth

metals

Group 7a = halogens

Group 8a = noble gases

Group 3b-2b = transition

metals

Diatomics = H2, N2, F2, O2,

I2, Cl2, Br2

Metalloids = B, Si, Ge, As,

Sb, Te


6

Problem 3:

Name the following compounds or give the symbol:

(a) Li2S

(b) NH4NO3

(c) Zinc (II) Oxide

(d) Tetracarbon pentachloride

(e) H2CO3

Net Ionic Equations Net ionic equations used to be really easy, all you had to was look for the word ‚aqueous‛.

But now you need to memorize the rules:

All ammonium, perchlorates, 1A, nitrates, acetates are always soluble

All chlorides, bromides, and iodides are soluble (B I C)

o except with Ag+, Pb2+, Cu+, and Hg22+ (H Ag-rid with his Cup at the Pb)

All fluorides are soluble (Fling)

o except with Pb2+ and elements in 2A (2AM Pb crawl)

All sulfates are soluble (Suffering)

o except with Ca2+, Sr2+, Ba2+, Ag+, and Pb2+ (Sr Ba Ca with hAgrid at the Pb)

Everything else is insoluble


7

Problem 4:

Five beakers sat on my bookshelf with the following five solutions. I accidentally dropped

sodium bromide into the beakers, oh no! Which one formed a precipitate? Write the net ionic

equation.

a) CuSO4 b) AgClO4 c) NH4Cl d) ZnSO4 e) CaI2

Oxidation-Reduction (Redox) Reactions

In a redox reaction there is a net movement of electrons from one reactant to another.

Oxidation – the LOSS of electrons.

Ex: Mg(s) Mg2+ + 2e-

Reduction – the GAIN of electrons.

Ex: ½O2(g) + 2e- O2-

The oxidizing agent is the element that is reduced (therefore oxidizing something else).

The reducing agent is the element that is oxidized (therefore reducing something else).

Oxidation Number

The oxidation number (O.N.) can also be referred to as the oxidation state and is designated

as the charge an atom would have if electrons in a compound were NOT shared but instead

just transferred completely.

For an atom in its elemental form, the ON is zero.

For a monatomic ion, the ON is just the charge.

The sum of the ON values of the atoms in a polyatomic molecule must equal the overall

charge of the molecule (which may be zero if it’s neutral).


8

Rules for specific atoms in the periodic table groups:

Group 1A elements have an ON of +1.

Group 2A elements have an ON of +2.

Hydrogen has an ON of +1 when found with a NONmetal. It has a ON of -1 when found

with metals and boron.

Fluorine has a -1 in all compounds.

Oxygen has an ON of -2 in all compounds except peroxides (then it’s -1).

Group 7A have an ON of -1 when found with metals, nonmetals (except oxygen), and

other halogens lower in the group.

Most elements have variable oxidation states which is determined per compound

Problem 5:

Determine the oxidation of carbon in the following molecules:

i) CO2 ii) C2 iii) H2CO2 iv) C2H6 V) HCO3

a) 3, 6, 2, -3, 2 b) 4, 0, 2, -3, 4 c) 4, 0, 2, 4, -2 d) 2, 2, 4, 3, 4 e) 4, 0, 1, 3, 4

Mole A mole, also known as Avagadro’s number, is equal to 6.02x1023 atoms/mole.

You can have a mole of anything- atoms, bongs, friends. The same concept as a dozen

For each atom or molecule there is a specific mass, called molar mass, that is the weight of a

mole of that atom or molecule

Ex. The molar mass of helium is 4.003 grams/mole.

The atomic mass of one compound can be determined from the atomic masses of the

elements within the compound.

Ex. The molar mass of water (H2O) is 18.02; therefore 1 mole of water weighs 18.02

grams.

Mole Map:


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Stoichiometry When balancing an equation, the numbers in front of each molecule are known as the

stoichiometric coefficients. They provide information on how much of a molecule will react

or form.

Ex: C2H4 + 3O2 → 2H2O + 2CO2, we know that for every mole of C2H4 that reacts, 2 moles of

H2O are formed and 3 moles of O2 react.

You can use these ratios to find final number of moles.

Ex: If you start with 3.5 moles of C2H4, 7 moles of CO2 will form

3.5 mol C2H4 x 2

2 4

2 mol CO

1 mol C H

= 7 moles of CO2

When two compounds are reacting, one will often be a limiting reactant meaning that there

was not enough of it so it limited the amount of product formed. The other reactant is

known as the excess reactant.

We never actually make as much in lab as we hope because we’re human and stuff. How

much we actually make is known as the actual yield. You can find the percent yield of your

reaction through the following equation:

%100Yield lTheoretica

Yield Actual YieldPercent

Problem 6:

The label on a bottle of purple drank says that the contents are 4.20% by mass lil’ Wayne and

the purple drank has a density of 1.1235 g/mL. How many molecules of lil’ Wayne are in a 2.00

liter bottle of purple drank? (shockingly, lil’ Wayne has a molar mass of 420 g/mol)

a) 3.65 x 1025 b) 9.23 x 1025 c) 1.35 x 1023 d) 5.68 x 1025 e) A milli


10

Problem 7:

A 75 gram sample of Tutorzonington composed of iron and other metals was dropped into

hydrochloric acid to produce iron (III) chloride and 1.2 grams of hydrogen gas. What is the

percent by mass of iron in Tutorzonington?

a) 39.6% b) 93.5% c) 12.0% d) 72.3% e) 55.2%

Problem 8:

Calcium hydride reacts with water to produce calcium hydroxide and hydrogen gas. Given that

we have 5.67 g of calcium hydride and 6.89 g of water, how much excess reactant is there?

a) 3.08 grams b) 4.85 grams c) 11.3 grams d) 2.04 grams e) 4.20 grams


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Empirical Formula

Defined as the lowest ratio of atoms to one another in a compound.

To find an empirical formula follow these steps:

1. Find the mass of all atoms involved

2. Convert the mass to moles

3. Divide the by the smallest number of moles

If the problem asks for a Molecular Formula, follow the steps above then:

4. Divide the molar mass of the molecular formula by the molar mass of the empirical

formula

5. Multiply the empirical formula by this number (It should be a whole number)

If the final coefficients are fractions, multiply all of them until whole numbers are found

Many compounds exist as hydrates – meaning that water molecules are attached to them.

These show up in empirical formula questions often.

Problem 9:

A certain chemical is made of carbon, hydrogen, and oxygen. .4375 grams of carbon dioxide and

.179 grams of water are produced from a .378 gram sample and the molar mass is 228 g/mol,

what is the molecular formula?

a) C6H12O9 b) C2H4O3 c) C1H2O1.5 d) C3H6O5 e) C8H2O3


12

Problem 10:

You start with 0.904g of Magnesium Sulfate hydrate. After mixing it with sodium hydroxide,

.521 g of Na2SO4 were produced. How many water molecules were in the hydrated Magnesium

Sulfate?

a) 3 b) 4 c) 5 d) 6 e) 7

Problem 11:

Pyro Pete decides to heat up a mixture of calcium sulfate octahydrate (280.3 g/mol) and

strontium sulfate tetrahydrate (255.7 g/mol) until all water is lost. Initially, the weight of the

mixture was 6.030 g. After, the anhydrous compound weighed 3.042 g. What was the percent by

mass of calcium sulfate octahydrate in the mixture?

a) 4.2 % b) 23.2 % c) 50.0 % d) 76.8 % e) 92.0 %


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Molarity and Titrations

Another way to calculate the moles of a compound is using the molarity (M). M = mol

L

Using the concepts in this packet, you can go from molarity of one compound to moles of

that compound to moles of another compound and back to molarity.

Remember M1V1 = M2V2 ! BUT with acids and bases it is important to note that for every

one ‘H’ there must be one ‘OH.’ i.e. H2SO4 is titrated by 2 moles of NaOH

In other words, when using the above equation, multiply by the subscript

1 1 2 2# ( )( ) # ( )( )H OH

M V M V

Ex: 50 ml of .5 M Ca(OH)2 titrated by 30 ml of ?M HCl

Problem 12:

If 13 grams of calcium are mixed with 500 mL of 2.5 M HBr, what concentration of acid remains

after the reaction is completed. (assume the products are calcium bromide and hydrogen gas)

a) 2.3 M b) 3.7 M c) 1.2 M d) 5.1 M e) .72 M


14

Problem 13:

When 35 ml of 2.70 M NaNO3 is mixed with 70 ml of 1.2 M Ba(NO3)2, what concentration of

nitrate ions is produced?

a) 4.20 M b) 1.27 M c) 2.50 M d) 3.82 M e) .950 M

Problem 14:

If a 420ml solution of NaOH is used to titrate 350ml of HCl and 250ml of that same HCl solution

is used to titrate 510 ml of .5M Ba(OH)2, what is the molarity of the sodium hydroxide?

a) 2.04 M b) 1.27 M c) 1.70 M d) 3.89 M e) 4.20 M


15

Energy

The change in energy of a system is equal to the heat plus the work done by the system.

E=q + w

Heat is negative if it ___________________ heat and positive when it ________________ heat.

Work is negative when the reaction ‚releases‛ work (does work on the surroundings) and

positive if it ‚absorbs‛ work or the work is done ON the reaction.

An extra equation you might need to know: w = -P V where w is work, P is pressure

and ∆V is change in volume. 1 atm * L = 101.325 J

Calculating Heat (Calorimetry)

To calculate heat use qrxn = M x C x T, where, m is mass(g), T is change in temperature (°C

or K) calculated by T = TF - TI and C is the specific heat capacity.

Specific heat capacity is the amount of heat needed to change the temperature of 1 gram of

substance by 1 degree Celsius.

The amount of heat lost (exothermic, - ) by a system equals the amount of heat gained

(endothermic, + ) by the surroundings, and vice versa

q rxn = - q Surroundings

CH2O= 4.184J

g*C, 1 calorie = 4.184 J, 1 Calorie = 1000 calories

q

H=quantity

rxn

Problem 15:

An insulated cup holding 625 g of Gatorade is filled with excess ice at 0°C. The specific heat of

the drink is 4.184 J/g°C. If 186 g of ice melted and it takes 400 J to melt 1.00 g of ice at 0°C, what

was the initial temperature of the Gatorade.

a) 16.2 °C b) 21.7 °C c) 28.5 °C d) 34.9 °C e) 42.3 °C


16

Metal and Water

A metal and water experiment is the basic type of heat transfer.

The key words to look for are specific heat capacity of the metal or compound.

qmetal = - qwater

Bomb Calorimetry

A bomb calorimetry experiment is done under constant volume.

The key words to look for are heat capacity of the bomb or calorimeter.

(qbomb + qwater) = - qrxn

Coffee Cup Calorimetry

A coffee cup calorimetry experiment is done under constant pressure.

The key phrase to look for is specific heat capacity of the solution

qsoln = - qrxn

Make sure to use the mass of solution

Note: q

H=quantity

rxn quantity is moles or grams of what is reacting


17

Problem 16:

When 54.0 grams of NaF are combined with 200 grams of water in a calorimeter, the

temperature of the solution increases from 22.8 °C to 29.3 °C. If the solution has the same

specific heat capacity as water, what is the enthalpy change of the reaction?

a) -5.37 kJ

mol b) 5.37 kJ

mol c) -4.23 kJ

mol d) 4.23 kJ

mol e) 1.27 kJ

mol

Problem 17:

One day while I was tweezing my eyebrows with cold 20g tweezers at 20 °C I dropped them

into 40 g of my hot coffee at 80 °C. If specific heat capacity of the tweezers is .85 J/g∙k and coffee

has the same specific heat as water, what was the final temperature of the tweezer-coffee?

a) 91.3 °C b) 74.5 °C c) 127 °C d) 32.4 °C e) @*$%\ Calorimetry


18

Problem 18:

I poured 30 grams of Jack Daniels in 100 ml of coke (d = 1 g/ml) at 25 °C in a calorimeter with a

heat capacity of 12.5 J/°C. The specific heat capacity of the jack and coke was 4.20 J/g∙°C and the

final temperature of the mixture was 22°C. How much heat was transfered in this mixture?

a) -1.30 kJ b) 1.30 kJ c) -1.68 kJ d) 1.68 kJ e) 1.26 kJ

Problem 19:

150ml of 1.5 M HBr and 75ml of 3.0 M KOH are mixed in a calorimeter. What is the final

temperature of the mixture if Hneutralization = -57KJ per mole of water formed and they started at

23oC? (Density and specific heat of the solution are the same as they would be for water)

a) 23.6 °C b) 58.3 °C c) 29.6 °C d) 92.4 °C e) 36.6 °C


19

Hess’s Law

Hess’s law is a fancy way of saying you can add equations together as long as you add their

heats of reaction to get the overall ∆Hrxn.

If you double a reaction, you must double the heat; if you flip a reaction, you flip the sign of

the heat.

To find the ∆Hrxn follow these simple steps:

Choose a molecule in your ‚target‛ reaction and work with the given equations to get

that molecule on the correct side, multiplying ∆H’s as you go.

Repeat until all molecules are correctly placed.

Add their ∆H’s up and done.

NOTE: If a molecule shows up in multiple equations, do that one LAST

Problem 20:

Determine the heat of reaction for the oxidation of iron 4 Fe(s) + 3 O2(g) → 2 Fe

2O

3(s)

2 Fe(s) + 6 H2O(l) → 2 Fe(OH)

3(s) + 3 H

2(g) ΔH = +321.8 kJ

2 H2O(l) → 2 H

2(g) + O

2(g) ΔH = +571.7 kJ

Fe2O

3(s) + 3 H

2O(l) → 2 Fe(OH)

3(s) ΔH = +288.6 kJ

a) 1650 kJ b) -1650 kJ c) -538.5 kJ d) 538.5 kJ e) 2614 kJ


20

Using Heats of Formation to Determine Heats of Reaction

The heat of formation, ΔHf, is the heat energy produced when one mole of a compound is

formed from its elements.

Ex.: Na (s) + ½Cl2 (g) → NaCl (s), ΔHf = -41.1 kJ

ΔHf = 0 for elements/compounds in their natural state (i.e. H2(g) , Xe(g) , Na(s) , etc)

To calculate ∆Hrxn from ΔHf subtract the reactants from products.

rxn f fproducts reactantsΔH = mΔH - nΔH

where m and n stand for the moles of each compound.

Problem 21:

The standard heat of formation of solid calcium chloride corresponds to which one of the

following equations?

(a) Ca (s) + 2 Cl- (aq) → CaCl2 (s)

(b) Ca2+ (aq) + 2 Cl- (aq) → BaBr2 (s)

(c) Ca (s) + Cl2 (aq) → BaBr2 (s)

(d) CaCl2 (s) → Ca2+ (aq) + 2 Cl- (aq)

(e) Ca (s) + Cl2 (g) → CaCl2 (s)

Problem 22:

Calculate ΔHrxn for the following reaction, using the info given:

3 2 2 2NH O NO Hg g g g

ΔHf NH3 = -46.2 kJ/mol, ΔHf NO2 = 33.9 kJ/mol

a) 80.1 kJ b) 160 kJ c) -80.1 kJ d) -160 kJ e) 194 kJ


21

Problem 23:

ErIn3 is formed via the following reaction

ErO3 + 3H2In => ErIn3 + 3H2O

Determine the enthalpy change of this reaction using the following data and the ∆H°f of water is

-307 kJ/mol.

Awesome + H2In => 1/3 ErIn3 ∆H = 147 kJ/mol

8 Awesome + 3O2 => 4THC + 2ErO3 ∆H = -1650 kJ/mol

Awesome => 2 THC + 3H2 ∆H = 75 kJ/mol

a) 420 kJ b) 567 kJ c) 127 kJ d) -1428 kJ e) -258 kJ

Thanks for Coming;

Email me questions!

Good Luck on your Test!


22

Spring 2012 CHM2045 Exam 1 Practice Problems

1. If you mix 400 ml of 1.4 M CaCl2 with 200 ml of 3.6 M CaCl2, what is the molarity of the

calcium chloride in the final solution?

a) 1.2 M b) 2.1 M c) 4.3 M d) 3.8 M e) .85 M

2. Which of the following has both ionic and covalent bonds?

a) NaCl b) NaSO4 c) SO3 d) H2O e) MgO

3. Phosphorus has two isotopes weighing 32.067 amu and 29.965 amu. What percentage is the

heavier isotope?

a) 48 % b) 56 % c) 52% d) 24 % e) 76 %

4. When KCl reacts with H2CO3, HCl and K2CO3 are formed. What volume of .550 M acid is

produced from 20 grams of KCl?

a) 100 mL b) 200 mL c) 300 mL d) 400 mL e) 500mL

5. If .15 L of .60 M Ba(OH)2 reacts with 750 ml of .10 M hydroiodic acid, what molarity of

barium iodide is formed?

a) .042 M b) .064 M c) .087 M d) .14 M e) .25 M

6. When 1.0 gram of popcorn is popped in a constant-pressure calorimeter with a heat capacity

of 2.20 kJ/°C, the temperature of the calorimeter is increased by 4.20 °C. How many Calories

are in 100 grams of popcorn?

a) 924 Calories b) 127 Calories c) 221 Calories d) 584 Calories e) 300 Calories

7. A 15.0 g sample of an unknown compound was heated to 475 K before being dumped inside

a coffee-cup calorimeter containing 185.0 g of water at 232 K, What is the final temperature

of the mixture? The specific heat capacity of the unknown compound is 0.803*

J

g K.

a) 100 K b) 236 °C c) 100 °C d) 236 K e) 420 °C


23

8. What is the standard enthalpy change for the following reaction

2C (s) + 2H2O (g) → CH4 (g) + CO2 (g)

from the standard enthalpies below?

C (s) + H2O (l) → CO (g) + H2 (g) ∆Ho = 149.8 KJ

H2O (l) → H2O (g) ∆Ho = 37 KJ

CO (g) + H2O (g) → CO2 (g) + H2 (g) ∆Ho = -41.2 KJ

CH4 (g) + H2O (g) → 3H2 (g) + CO (g) ∆Ho = 206.1 KJ

a) 217 kJ b) 13.4 kJ c) -45.6 kJ d) -127 kJ e) -21.7 kJ

9. Calculate the ∆Hf of ammonia from the following reactions:

2 NO2 2 NO + O2 ∆Hrxn = -345 kJ/mol

2 NH3 + O2 2 NO + 3 H2 ∆Hrxn = 546 kJ/mol

N2 + 2 O2 2NO2 ∆Hrxn = 127 kJ/mol

a) - 382 kJ b) + 382 kJ c) - 328 kJ d) + 328 kJ e) + 420 kJ

10. Phosphorous is naturally found as P4 and oxygen as O2. How many grams of oxygen

contain the same number of atoms as 15.7 grams of phosphorous?

a)16.2 g b) 32. 4 g c) 24.3 g d) 8.11 g e) 4.05 g

11. 3.7 grams of hydrogen reacted with nitrogen to make ammonia. The ammonia was then

reacted with sulfuric acid to make ammonium sulfate. How much ammonium sulfate was

produced?

a) 140 g b) 178 g c) 192 g d) 123 g e) 106 g

12. What is the molarity of NaCl in a solution prepared by mixing 400mL of 0.05 M NaCl with

350mL of 0.07 M NaCl?

a) .89 M b) 2.3 M c) .045 M d) .059 M e) .23 M

13. A compound contains 19.67% carbon, 1.64% hydrogen, and 78.69% oxygen, by mass. A

0.050 mole sample of this compound weighs 6.10 g. What is the molecular formula of this

compound?

a) CHO3 b) CHO2 c) C2H2O6 d) C2H2O4 e)C3H3O9

14. What are the oxidation numbers of P, S, and Cl in H2PO 2

, H2S, and KClO4?

a) +1, -2, +7 b) +1, -1, +5 c) +3, -1, +7 d) +1, -2, +5 e) +3, -2, +7


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15. What is the net ionic eqaution for when sodium chloride and mercury nitrate react?

a) 2NaCl (aq) + Hgg(NO3)2 (aq) → 2NaNO3 (aq)+ Hg2Cl2 (s)

b) 2NaCl (aq) + Hgg(NO3)2 (aq) → 2Na+ (aq) + 2NO3+ (aq)+ Hg2Cl2 (s)

c) 2NaCl (aq) + Hgg2+ (aq) → 2Na+ (aq) + Hg2Cl2 (s)

d) 2Na+ (aq) + 2Cl- (aq) + Hgg2+ (aq) + 2NO3- (aq) → 2Na+ + 2NO3+ (aq) + Hg2Cl2 (s)

e) 2Cl- (aq) + Hg22+ (aq) → Hg2Cl2 (s)

16. 200.0 mL of 1.020 M HCl and 100.0 mL of 2.040 M NaOH, each at 17.40oC, are mixed in a

calorimeter. What is the final temperature of the mixture if ΔHneut = −57 kJ per mole of H2O

formed? (Assume density and specific heat of solution are the same as water)

a) 26. 7 °C b) 8.14 °C c) 11.6 °C d) 38.4 °C e) 20.2 °C

17. If 2.00 g of an unknown element X reacts with 5.00 g of another unknown element Z to

produce 7.00 g of a compound which has a formula X3Z4, and the atomic mass of Z is

135.0g/mol, what’s the molar mass of X?

a) 135 g/mol b) 72.0 g/mol c) 18.0 g/mol d) 420 g/mol e) 5.0 g/mol

18. What is the name of the following compound MnO2*5H2O

a) Manganese Oxide Hexahydrate

b) Magnesium (IV) Pentahydrate

c) Manganese oxygen and 5 waters

d) Manganese (IV) Oxide Pentahydrate

e) Magnesium (II) Hexahydrate

19. Given the thermochemical information:

∆Ho (H2O (l)) = − 285.8 kJ/mol ∆Ho (C2H2 (g)) = − 26.7 kJ/mol ∆Ho (CO2 (g)) = − 393.5 kJ/mol.

The molar heat of combustion of acetylene, C2H2 (gas), is closest to?

a) -2092 kJ/mol b) +2092 kJ/mol c) -1046 kJ/mol d) 1046 kJ/mol e) -523.5 kJ/mol

20. If 0.520 grams of bromine and .160 grams of ammonia react according to the unbalanced

equation below, what is the amount of excess reactant?

Br2 (g) + NH3 (g) → NH4Br (s) + N2 (g)

a) .089 g b) .234 g c) .127 g d) .420 g e) .0123 g

21. How many atoms are in 25.35 g of N2S?

a) 7.62x1023 atoms b) 1.96x1023 atoms c) 2.54x1023 atoms d) 5.34x1022 atoms e) 3.44x1022 atoms


25

22. In the reaction, SF4 + F2 → SF6, sulfur goes from an oxidation state of ___ to an oxidation

state of ___.

a) +4, +5 b) +6, +4 c) +4, +6 d) +2, +3 e) +3, +2

23. If, during the thermal decomposition of silver oxide, 430 g Ag is produced, what is the total

heat transferred in kJ? ∆Hrxn = 31.1 kJ/mol

a) 25 kJ b) 35 kJ c) 56 kJ d) 62 kJ e) 73 kJ

24. What is the ∆Hrxn for the given overall reaction?

½MAN + BEER HANGOVER

PARTY MAN + 2BEER ∆H = - 45.6 kJ

½ PARTY + VODKA HANGOVER + GIRL ∆H = -123.6 kJ

2GIRL 2VODKA ∆H = 75.8 kJ

a) -324 kJ b) -212 kJ c) -114 kJ d) -63 kJ e) -24 kJ

25. Which of the following statements are correct when describing a mole of a substance?

I. A mole of any substance contains 6.022 x 1023 entities

II. A mole contains a substance’s atomic weight in grams

III. The mole is derived from 12 g of carbon-12

IV. 1 mol H2O contains 6.022 x 1023 atoms

a. I only

b. I and II

c. I, II, and III

d. I, III, and IV

e. All Choices

26. Which of the following assumptions are correct if a reaction is exothermic?

I. Heat is released

II. Hfinal > Hintial

III. The reaction will be slow

IV. If ∆H is negative enough, liquid water would turn to ice.

a. I only

b. II and III

c. I and IV

d. III only

e. All Choices


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27. A flask weighs 130 grams when empty and 375 grams when filled with water. If the same

flask weighs 325 grams when filled with sulfuric acid, whats the density of the sulfuric acid?

a) .867 g/ml b) .796 g/ml c) 1.33 g/ml d) 4.20 g/ml e) .542 g/ml

28. Write the net ionic equation for the reaction between silver (I) nitrate with calcium chloride

to form silver (I) chloride and calcium nitrate.

b) 2AgNO3 (aq) + CaCl2 (aq) →2AgCl (s) + Ca(NO3)2 (aq)

c) 2Ag+ (aq) + 2NO3- (aq) + CaCl2 (aq) → 2AgCl (s) + Ca(NO3)2 (aq)

d) 2Ag+ (aq) + 2NO3- (aq) + Ca2+ (aq) + 2Cl- (aq) → 2AgCl (s) + Ca(NO3)2 (aq)

e) 2Ag+ (aq) + 2NO3- (aq) + Ca2+ (aq) + 2Cl- (aq) → 2AgCl (s) + Ca2+ (aq) + 2NO3- (aq)

f) Ag+ (aq) + Cl- (aq) → AgCl (s)

29. A .70 g nugget containing chlorine is dissolved in heat. When sodium iodide is added, .25

grams of NaCl precipitates out. What’s the mass percent of chlorine in the nugget?

a) 36% b) 21.7% c) 87% d) 16% e) 90%

30. The following is an unbalanced equation needed to answer the following question:

CO(g) + H2(g) CH3OH(l)

If 70.1 kg of gaseous carbon monoxide reacts with 7.3 kg of gaseous hydrogen, causing the

production of 40.3 kg of methanol (CH3OH), what is the percent yield of methanol?

a) 35% b) 50 % c) 70 % d) 85 % e) 96 %

31. A 420g mixture of butane (C4H10) and butene (C4H8) is combusted in air to make carbon

dioxide and water. If 555 grams of water are formed, how much butane was in the mixture?

a) 192 g b) 234 g c) 127 g d) 57.7 g e) 362 g

32. If 2.412 g of anhydrous SrSO4 is obtained after reacting 3.028 g of SrCl2* xH2O with sulfuric

acid, what is the value of x in the hydrate formula?

a) 1 b) 2 c) 3 d) 4 e) 5

33. After an unknown mass of calcium is dropped into a 600 mL sample of 2.0 M HCl, the

concentration of the acid solution is 1.43 M. What mass of calcium must have been dropped

into the sample, assuming all the calcium reacted? (Volume remains unchanged/Products

are hydrogen gas and calcium chloride)

a) 2.34 g b) 6.86 g c) 9.32 g d) 13.44 g e) 17.16 g


27

34. An insulated cup holding 412 g of 26°C Mike’s Hard Lemonade is filled with excess ice at

0°C. The specific heat of the drink is 4.184 J/g°C. If some of the ice remains, determine how

much of the ice has melted. To melt 1.3 g of ice at 0°C takes 350 J. (Ignore the cup’s heat

capacity)

a) 112 g b) 123 g c) 158 g d) 167 g e) 181 g

35. Which of the following statements is true?

a) an oxidation number is assigned to every polyatomic ion

b) the charge of a polyatomic ion is a property of only certain atoms constructing the ion

c) a charge of -1 on a polyatomic ion means the ion’s oxidation state is -1 as well

d) the oxidation number is the charge assigned to each atom composing a polyatomic ion

e) the charge of a polyatomic ion is not a real physical property

36. How many chlorines are in 56.77 g of CH2Cl2?

a) 1.22 x 1023 b) 2.38 x 1023 c) 8.05 x 1023 d) 4.03 x 1023 e) 2.01 x 1024

37. An unknown concentration of 250 mL of MgCl2 is added to a 120 mL sample of 0.720 M KCl.

The final chlorine ion concentration is 1.56 M. What was the unknown concentration of

MgCl2?

a) 0.98 M b) 1.23 M c) 1.55 M d) 1.78 M e) 2.11 M

38. Which of the following ionic solids would dissolve completely in water?

a) Ca3(PO4)2 b) Rb2S c) PbCl2 d) MgCO3 e) Mg(OH)2

39. The molar energy for combustion of 45.6 g of heptane (C7H16) was found to be -488 kJ/mol. If

the heat capacity of the bomb calorimeter is 6.1 kJ/K and the initial temperature was 312 K,

what was the temperature after combustion?

a) 348 K b) 356 K c) 367 K d) 386 K e) 413 K

40. Which of the following ionic compounds is written correctly?

I. (NH4)Br II. AgCl2 III. CaSe IV. Al(ClO4)3

a) I only b) I and II c) I and IV d) III only e) III and IV

Answers: BBAEA CDEAD ADCAE ABDCE ACDDC CBEBC DDBDD CABAE

Detailed solutions can be found at apps.tutoringzone.com!


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Documents

Spring 2012 CHM2045 Exam 1