FINAL EXAM marathon

Stoichiometry

100

When 2.00 mol of H₂ reacts completely with excess O₂ according to the reaction below, how many molecules of H₂O are produced?

2H₂ + O₂ → 2H₂O

A) 2.0 molecules

B) 1.20 * 10²⁴ molecules

C) 2.41 * 10²⁴ molecules

D) 3.01 * 10²⁴ molecules

B 

exp: Multiply # of moles (4 mol H) by Avogadro's number (6.022e23)

200

Chlorine occurs naturally as two isotopes:

1) Cl-35 (34.97 amu)

2) Cl-37 (36.97 amu)

If average atomic mass of chlorine is 35.45 amu, what is the percent abundance of Cl-35 in naturally occurring chlorine?

A) 23.5%

B) 50.0%

C) 75.8%

D) 82.0%

C (see slide #7)

300

Oxcarbazepine is an anticonvulsant drug also commonly used to treat bipolar disorder (C₁₅H₁₂N₂O₂). What mass of Nitrogen (m.w. = 14.007 g/mol) is in 15.283 x 10^-4 g of Oxcarbazepine?

A) 3.39×10⁻⁴ g

B) 1.70×10⁻⁴ g

C) 1.53×10⁻⁴ g

D) 7.65×10⁻⁵ g

B (see slide #5)

400

Aluminum reacts with chlorine gas to form aluminum chloride:

2Al+3Cl₂ → 2AlCl₃   

If 10.0 g Al reacts with 20.0 g Cl₂, what is the mass of AlCl₃ produced?

A) 25.0 g

B) 33.3 g

C) 40.0 g

D) 50.0 g

A (see slide #8)

500

A 0.842 g sample of a compound containing only C, H, and N is combusted in excess oxygen gas (O₂). The combustion produces 1.76 g CO₂ and 0.721 g H₂O. A separate analysis shows the compound is 18.2% nitrogen by mass.

What is the empirical formula of the compound?

A) C₁₁H₂₂N₃

B) C₅H₁₀N₂

C) C₄H₁₀N₂

D) C₃H₆N

A (see slide #6)

Atomic & Electronic Structure

100

On the blank periodic table (slide #10), label the following

...

Alkali metals

Alkaline earth metals

Transition metals

Halogens

Noble gases

See slide #11 for answer

200

Which emission spectrum line in the hydrogen spectrum occurs at the highest frequency? 

A) n = 3 to n = 1

B) n = 4 to n = 2

C) n = 7 to n = 5

D) n = 10 to n = 8

A - the larger drops occur between lower energy levels. 

300

What is the ground state electron configuration for Cr+?

A) [Ar]4s¹3d⁵

B) [Ar]4s²3d⁴

C) [Ar]4s¹3d⁴

D) [Ar]3d⁵

D) [Ar]3d⁵

400

Draw a diagram representing the occupation of each of the hybrid orbitals for C in the molecule CH₄. 

See slide 19. 

500

What is the wavelength (in nm) of the photon emitted when an electron in a hydrogen atom transitions from n = 5 to n = 2?

R_H=1.097×10⁷ m^-1

A) 434 nm

B) 486 nm

C) 656 nm

D) 4.34 nm

A (see slide 19)

Nomenclature & Naming

100

What is the correct name for CaCl₂?

A) Calcium (I) chloride

B) Monocalcium dichloride

C) Calcium dichloride

D) Calcium chloride

D - ionic compounds with group 1 & 2 metals do not need to contain charge. Ionic compounds also do not specify quantity in the name. 

200

What is the correct name for (NH₄)₂SO₄?

A) Ammonium sulfide

B) Ammonium sulfate

C) Diammonium sulfate

D) Ammonia sulfate

B - Contains a polyatomic, treat this as if it were ionic. 

300

What is the correct name for Cu₂O?

A) Copper(I) oxide

B) Copper(II) oxide

C) Dicopper monoxide

D) Copper oxide

A - ionic compounds with a transition metal need to specify charge within the name. 

400

What is the correct name for N₂O₂?

A) Nitrogen oxide

B) Nitrogen (II) oxide

C) Dinitrogen dioxide

D) Nitrogen dioxide

C - covalent compounds specify quantity and not charge. 

500

Name all polyatomics that you are expected to know (you may use your notes but NOT slides/the internet). You must name at least 23. 

acetate    CH3CO2 -

ammonium    NH4 +

cyanide    CN -

hypochlorite    ClO -

chlorate    ClO3 -

perchlorate    ClO4 -

chlorite    ClO2 -

dihydrogen phosphate    H2PO4 -

hydrogen carbonate/bicarbonate    HCO3 -

hydrogen sulfate/bisulfate    HSO4 -

hydroxide    OH -

permanganate    MnO4 -

nitrite    NO2 -

nitrate    NO3 -

carbonate    CO3 2-

chromate    CrO4 2-

dichromate    Cr2O7 2-

peroxide    O2 2-

hydrogen phosphate    HPO4 2-

sulfite    SO3 2-

sulfate    SO4 2-

thiosulfate    S2O3 2-

phosphate    PO4 3-

bromite    BrO2 -

bromate    BrO3 -

hypobromite    BrO -

perbromate    BrO4 -

Thermochemistry

100

Is the following an exothermic or endothermic process, if the system is your body? What about if the system is the air around you? 

You sit near a sunny windowsill because you feel cold.

Your body is the system -> Endothermic. You are absorbing the heat from your surroundings. 

The air around you is the system -> Exothermic. The air is losing heat to you. 

200

A gas absorbs 125 kJ of heat while simultaneously doing 40.0 kJ of work on the surroundings during expansion. What is the change in internal energy (ΔE) of the system?

A) +165 kJ

B) − 85.0 kJ

C) + 85.0 kJ

D) −165 kJ

C (use the equation energy = work + heat). 

300

The standard enthalpy of combustion of ethanol (C₂H₅OH, l) is −1367 kJ/mol.

What is the total heat released (in kJ) when 23.0 g of ethanol is completely combusted in the following equation?

C₂H₅OH (l) + 3O₂ (g) -> CO₂ (g) + 3H₂O (l)

A) −341 kJ
B) −682 kJ
C) −1025 kJ
D) −1367 kJ

B (see slide 20). 

400

Using the given thermochemical data, what is the enthalpy of formation (ΔHf) for the given reaction? 

2CH₃OH (l) + O₂ (g) -> HC₂H₃O₂ (l) + 2H₂O (l)

Table (ΔHf) in kJ/mol: 

CH₃OH (l) = -238

HC₂H₃O₂ (l) = -487

 H₂O (l)= -286

A) 583 kJ/mol

B) 535 kJ/mol

C) - 583 kJ/mol

D) - 535 kJ/mol

C (see slide 21)

500

Slide 22

Slide 23

Structure & Bonding

100

What kind of bond do each of the following compounds contain? Specify polarity. 

1) NaCl

2) CuCl₂

3) Br₂

4) H₂O

5) NaBr

6) NO₂

1) NaCl

2) CuCl₂ - ionic

3) Br₂ - nonpolar covalent

4) H₂O - polar covalent

5) NaBr - ionic

6) NO₂ - polar(ish) covalent

200

Draw the dipole moments of the following molecules, then state whether or not the molecules are polar or nonpolar and how you know (see slide 16). 

See slide 17. 

300

Label the following electron geometries: (see slide 14)

See slide 15

400

Draw a molecule with ALL THREE MOLECULAR GEOMETRIES: tetrahedral, trigonal planar, trigonal pyramidal

Answers vary. See slide #9 for an example. 

500

Fill out the following table (see slide #12)

See slide #13 for answer