CHM 151 Practice Cumulative Final Notes

Significant Figures

• Question 1: How many significant figures are in the number $2.0 \times 10^4$?

  • Answer: (B) 2

Unit Conversions

• Question 2: Which of the following is equivalent to 5.0 cm?

  • (A) 50,000. nm

  • (B) 50.0 mm

  • (C) 0.50 m

  • (D) 0.00050 km

  • Answer: (A) 50,000. nm

Significant Figures and Volume Calculation

• Question 3: Determining the volume of a cube:

  • Side length measured in inches: 1.25 in

  • Side length in cm: 3.175 cm

  • Calculator result after cubing: 32.005984375

  • Reported volume with correct significant figures?

  • (A) 32 cm3

  • (B) 32.0 cm3

  • (C) 32.01 cm3

  • (D) 32.006 cm3

  • Answer: (B) 32.0 cm3

Moles and Caffeine Consumption

• Question 4: Caffeine content in a cup of coffee: 95 mg (C8H10N4O2, molar mass = 194.19 g/mol)

  • How many cups to ingest 0.00352 moles of caffeine?

  • (A) 0.0035 cups

  • (B) 0.68 cups

  • (C) 7.2 cups

  • (D) 65 cups

  • Answer: (C) 7.2 cups

Dosage Calculation

• Question 5: Dosage calculation based on body weight:

  • Person weighs 145 lb

  • Recommended dosage: 10.0 mg per kilogram of body weight

  • (1 lb = 454 g)

  • (A) 6.6 mg

  • (B) 32 mg

  • (C) 319 mg

  • (D) 658 mg

  • Answer: (D) 658 mg

  • Convert pounds to grams, then grams to kilograms, then multiply by the dosage.

Atomic Measurement

• Question 6: Bismuth (Bi) atom diameter: approximately 320. picometers (pm)

  • How many bismuth atoms to span 1.00 cm side-by-side?

  • (1 pm = $1 \times 10^{-12}$ m)

  • (A) $3.13 \times 10^{-17}$ atoms

  • (B) $3.20 \times 10^{-8}$ atoms

  • (C) $3.13 \times 10^7$ atoms

  • (D) $3.20 \times 10^{12}$ atoms

  • Answer: (C) $3.13 \times 10^7$ atoms

Percent Error in Density Measurement

• Question 7: Density measurement by students:

  • Tina: 0.8029 g/mL

  • Bill: 0.7915 g/mL

  • Jordan: 0.7938 g/mL

  • Actual density: 0.7892 g/mL

  • Group’s percent error?

  • (A) 0.87%

  • (B) 8.7%

  • (C) 9.9%

  • (D) 87%

  • Answer: (A) 0.87%

  • Calculate the average density, then use the percent error formula: $\frac{|\text{experimental value} - \text{actual value}|}{\text{actual value}} \times 100$.

States of Matter and Temperature

• Question 8: Substance that exists as a gas at room temperature:

  • (A) melting point below room temperature, boiling point above room temperature

  • (B) melting point above room temperature, boiling point below room temperature

  • (C) both melting point and boiling point below room temperature

  • (D) both melting point and boiling point above room temperature

  • Answer: (C) both its melting point and its boiling point are below room temperature

Solutions

• Question 9: Correct description of a solution:

  • (A) A heterogeneous mixture of two or more substances.

  • (B) A homogeneous mixture of two or more substances.

  • (C) May be gaseous, solid, or liquid.

  • (D) answers (B) and (C) are both correct

  • Answer: (D) answers (B) and (C) are both correct

Electromagnetic Radiation

• Question 10: Statements about electromagnetic radiation (light):

  • (A) shorter wavelengths correspond to higher frequencies

  • (B) shorter wavelengths correspond to lower energies

  • (C) higher energies correspond to lower frequencies

  • (D) none of the above statements are correct
    *Answer: (A) shorter wavelengths correspond to higher frequencies
    *Recall that: $c = \lambda \nu$ $E = h \nu$

Nuclear Symbol

• Question 11: Correct nuclear symbol for atom with atomic number 13 and mass number 27:

  • (A) Al$\frac{27}{13}$

  • (B) Co$\frac{27}{13}$

  • (C) Al$\frac{13}{27}$

  • (D) Co$\frac{13}{27}$

  • Answer: (A) Al$\frac{27}{13}$

  • Atomic number is the subscript, mass number is the superscript, and Al is the element symbol for Aluminum.

Valence Electrons and Noble Gas Configuration

• Question 12: How many valence electrons must a selenium (Se) atom gain or lose to obtain a noble gas configuration?

  • (A) gain two

  • (B) gain three

  • (C) lose two

  • (D) lose three

  • Answer: (A) gain two

  • Selenium is in group 16, hence, it needs to gain two electrons to have a full octet like noble gases

Metal Ion and Orbital Filling Diagram

• Question 13: Metal ion consistent with orbital filling diagram:

  • (A) Mo$\text{2+}$

  • (B) Mn$\text{3+}$

  • (C) Ru$\text{2+}$

  • (D) Tc$\text{3+}$

  • Answer: (B) Mn$\text{3+}$

Atoms of Phosphorus in P2O5

• Question 14: How many atoms of phosphorus are in 1.28 grams of P2O5?

  • (A) $5.43 \times 10^{21}$ atoms of phosphorus

  • (B) $1.09 \times 10^{22}$ atoms of phosphorus

  • (C) $3.28 \times 10^{22}$ atoms of phosphorus

  • (D) $2.19 \times 10^{26}$ atoms of phosphorus

  • Answer: (B) $1.09 \times 10^{22}$ atoms of phosphorus

Average Atomic Mass

• Question 15: Two isotopes of an element:

  • Abundance of one isotope: 93.26%, atomic mass: 38.964 amu

  • Atomic mass of the second isotope: 40.962 amu
    *Determine the average (unified) atomic mass of this element.

  • Answer: (B) 39.099 amu

First Ionization Energies

• Question 16: Which group have the highest first ionization energies?

  • (A) Alkali metals

  • (B) Transition metals

  • (C) Halogens

  • (D) Alkaline earth metals

  • (E) Noble gases

  • Answer: (E) Noble gases

Electron Configuration

• Question 17: Which of the following is the electron configuration of an atom in the ground state?

  • (A) 1$\text{s}^{1}$ 2$\text{s}^{2}$

  • (B) 1$\text{s}^{2}$ 2$\text{s}^{1}$

  • (C) 1$\text{s}^{2}$ 2$\text{s}^{1}$ 2$\text{p}^{6}$

  • (D) 1$\text{s}^{2}$ 2$\text{s}^{2}$ 2$\text{p}^{5}$ 3$\text{s}^{2}$

  • (E) 1$\text{s}^{2}$ 2$\text{s}^{2}$ 2$\text{p}^{6}$ 3$\text{s}^{2}$ 3$\text{p}^{6}$ 4$\text{s}^{0}$ 3$\text{d}^{5}$

  • Answer: (B) 1$\text{s}^{2}$ 2$\text{s}^{1}$

Molecular Geometry of NH3

• Question 18: Given the Lewis structure of NH3, what is the molecular geometry of NH3?

  • (A) T-shaped

  • (B) trigonal planar

  • (C) square planar

  • (D) tetrahedral

  • (E) trigonal pyramidal

  • Answer: (E) trigonal pyramidal

Polyatomic Ion for Perchlorate

• Question 19: What is the correct polyatomic ion for perchlorate?

  • (A) ClO$\text{2}^{-1}$

  • (B) ClO$\text{3}^{-1}$

  • (C) ClO$\text{4}^{-1}$

  • (D) ClO$\text{3}^{2-}$

  • Answer: (C) ClO$\text{4}^{-1}$

Naming Ionic Compounds

• Question 20: The correct name for Cu3(PO4)2 is

  • (A) tricupric diphosphate

  • (B) copper phosphate

  • (C) copper(III) diphosphate

  • (D) copper(III) phosphate

  • (E) copper(II) phosphate

  • Answer: (E) copper(II) phosphate

Formula for Potassium Nitride

*Question 21: The formula for potassium nitride is

• (A) $\text{P}_{3}\text{N}$

• (B) $\text{K}_{3}\text{N}$

• (C) $\text{KNO}_{3}$

• (D) $\text{KNO}_{2}$

• (E) $\text{PN}$

• Answer: (B) $\text{K}_{3}\text{N}$

Sigma and Pi Bonds in Acrolein

• Question 22: Determine the number of sigma (σ) and pi (π) bonds in acrolein:

  • (A) 7 sigma, 2 pi

  • (B) 9 sigma, 2 pi

  • (C) 2 sigma, 7 pi

  • (D) 5 sigma, 2 pi

  • (E) 5 sigma, 4 pi

  • Answer: (A) 7 sigma, 2 pi

Non-Polar Molecules

• Question 23: Which one of the following molecules is overall non-polar?

  • (A) $\text{CH}_{3}\text{I}$

  • (B) $\text{CHBr}_{3}$

  • (C) $\text{CH}<em>{2}\text{Cl}</em>{2}$

  • (D) $\text{CF}_{4}$

  • (E) $\text{CO}$

  • Answer: (D) CF4

Ionic Compound

• Question 24: Which one of the following would you expect to be an ionic compound?

  • (A) $\text{MgBr}_{2}$

  • (B) $\text{SBr}_{2}$

  • (C) $\text{NBr}_{3}$

  • (D) $\text{CBr}_{4}$

  • Answer: (A) MgBr2

Polar Covalent Bond

• Question 25: A polar covalent bond would be expected to form between which of the following pairs of atoms?

  • (A) H and H

  • (B) Cl and C

  • (C) Na and F

  • (D) Fe and F

  • Answer: (B) Cl and C

Molecular Geometry of SCl2

• Question 26: What is the molecular geometry of sulfur dichloride (SCl2), given that sulfur is the central atom?

  • (A) linear

  • (B) bent

  • (C) tetrahedral

  • (D) trigonal planar

  • Answer: (B) bent

Molecular Formula Determination

• Question 27: The percent composition by mass of a compound is 76.0% C, 12.8% H, and 11.2% O. The molar mass of this compound is 284.5 g/mol. What is the molecular formula of the compound?

  • (A) C10H6O

  • (B) C9H18O

  • (C) C20H12O2

  • (D) C18H36O2

  • Answer: (D) C18H36O2

Balancing Chemical Equations

• Question 28: When the reaction below is properly balanced using the smallest set of whole-number coefficients, what is the coefficient on Cl2? __ CH4 + __ Cl2 → __ CCl4 + __ HCl

  • (A) 1

  • (B) 2

  • (C) 4

  • (D) 6

  • (E) 8

  • Answer: (C) 4

Percent Yield Calculation

• Question 29: If the reaction of 150 g of ammonia with 150 g of oxygen gas according to the following reaction yields 87 g of nitric oxide, what is the percent yield of this reaction? 4 NH3 (g) + 5 O2 (g) → 4 NO (g) + 6 H2O (g)

  • (A) 100%

  • (B) 77%

  • (C) 62%

  • (D) 49%

  • (E) 33%

  • Answer: (D) 49%

Strong Electrolytes

• Question 30: Which of the following is a strong electrolyte?

  • (A) HCl (hydrochloric acid)

  • (B) C6H12O6 (glucose)

  • (C) HC2H3O2 (acetic acid)

  • (D) CH3OH (methanol)

  • (E) N2 (nitrogen gas)

  • Answer: (A) HCl (hydrochloric acid)

Classifying Reactions

• Question 31: Classify the following reaction: CaBr2 (aq) + H2SO4 (aq) → CaSO4 (s) + 2 HBr (aq)

  • (A) Acid-base reaction

  • (B) Precipitation reaction

  • (C) Dissociation reaction

  • (D) Combustion reaction

  • (E) Single-displacement reaction

  • Answer: (B) Precipitation reaction

Products of Combustion Reaction

• Question 32: Choose two possible products of a combustion reaction.

  • (A) ammonia & water

  • (B) carbon dioxide & water

  • (C) an acid & a base

  • (D) oxygen gas & hydrogen gas

  • (E) water & a salt

  • Answer: (B) carbon dioxide & water

Molarity of a Solution

• Question 33: What is the molarity of a NaOH solution made by diluting 20.0 mL of a 1.50 M NaOH solution to a final volume of 50.0 mL?

  • (A) 0.015 M

  • (B) 0.60 M

  • (C) 3.75 M

  • (D) 24.0 M

  • Answer: (B) 0.60 M

Grams of Precipitate Formed

• Question 34: Calcium chloride (CaCl2) reacts with potassium carbonate (K2CO3) in a double-replacement reaction, part of which is shown below. CaCl2 (aq) + K2CO3 (aq) → How many grams of precipitate are formed when a solution containing 8.94 grams of calcium chloride is mixed with a solution containing excess potassium carbonate?

  • (A) 3.01 g

  • (B) 8.06 g

  • (C) 9.91 g

  • (D) 12.02 g

  • Answer: (B) 8.06 g

Mass of NaOH Needed

• Question 35: Given the reaction of NaOH (sodium hydroxide) and HC2H3O2 (acetic acid) shown below, what mass of NaOH is needed to fully neutralize 35.4 mL of a 1.70 M acetic acid solution? NaOH (aq) + HC2H3O2 (aq) →

  • (A) 0.8329 g

  • (B) 1.5045 g

  • (C) 2.4072 g

  • (D) 5.2059 g

  • Answer: (C) 2.4072 g

Enthalpy Change

• Question 36: When ammonium chloride is dissolved in water, the reaction vessel turns cold. This means:

  • (A) the process is endothermic.

  • (B) the process is exothermic.

  • (C) the total energy of the system + surroundings has decreased.

  • (D) the energy of both the system and the surroundings has increased.

  • (E) the energy of both the system and the surroundings has decreased.

  • Answer: (A) the process is endothermic.

  • Endothermic process absorbs heat, making the surroundings cold.

Ideal Gas

• Question 37: Which of the following statements is false for an ideal gas?

  • (A) The volume of an individual gas molecule is negligible compared to the distance between molecules.

  • (B) Gas molecules travel in curved paths, changing directions randomly.

  • (C) Individual gas molecules do not attract or repel one another.

  • (D) Collisions of gas molecules with each other or with the walls of the container are perfectly elastic.

  • Answer: (B) Gas molecules travel in curved paths, changing directions randomly.

  • Ideal gas molecules travel in straight paths until they collide.

Final Volume of Gas

• Question 38: A sample of an ideal gas with an initial temperature of 21°C at a volume of 12.5 L is cooled to –10°C under constant pressure conditions. What is the final volume of this gas?

  • (A) 5.95 L

  • (B) 11.2 L

  • (C) 13.9 L

  • (D) 26.3 L

  • Answer: (B) 11.2 L
    *Use Charles's Law: $\frac{V<em>1}{T</em>1} = \frac{V<em>2}{T</em>2}$, where temperatures must be in Kelvin.

Mass of NO Gas

• Question 39: Calculate the mass in grams of 3.55 L of NO gas at 52°C and 874 mmHg (1 atm = 760 mmHg).

  • (A) 0.153 g

  • (B) 4.59 g

  • (C) 6.53 g

  • (D) 7.04 g

  • (E) 24.24 g

  • Answer: (B) 4.59 g
    *Use the Ideal Gas Law: $PV = nRT$, then convert moles to grams using the molar mass of NO.

Specific Heat of Metal

• Question 40: A piece of metal with a mass of 48.342 g at an initial temperature of 108°C is placed into 50.00 g of water initially at 20.3°C. The final equilibrium temperature of the water is 34.6°C. Calculate the specific heat of the metal. (Given that the specific heat of water = 4.184 J/g⋅°C)

  • (A) 0.706 J/g⋅°C

  • (B) 0.788 J/g⋅°C

  • (C) 0.843 J/g⋅°C

  • (D) 1.19 J/g⋅°C

  • Answer: (A) 0.706 J/g⋅°C
    *Use the formula $q = mc\Delta T$, where $q<em>{\text{metal}} = -q</em>{\text{water}}$

Enthalpy Calculation

*Question 41: Calculate the $\Delta H$ for the reaction:
$\text{NO}<em>{2} (g) + \text{CO} (g) \rightarrow \text{CO}</em>{2} (g) + \text{NO} (g)$
using the following standard enthalpies of formation:

*Compound $\Delta H<em>{f}$ ° (kJ/mol) *CO (g) –111 *CO2 (g) –394 *NO (g) 90 *NO2 (g) 34 * (A) 339 kJ * (B) 381 kJ * (C) –227 kJ * (D) –339 kJ * (E) 227 kJ * Answer: (C) –227 kJ *Use Hess's Law: $\Delta H</em>{\text{rxn}} = \sum \Delta H<em>{f}^{\text{products}} - \sum \Delta H</em>{f}^{\text{reactants}}$