CHEM 1311 Exam 1 Review – Step-by-Step Study Guidance

Q1. What is the name of the statement: "In a chemical reaction, matter is neither created nor destroyed"?

Background

Topic: Laws of Chemistry

This question tests your knowledge of fundamental chemical laws, specifically those related to conservation and atomic theory.

Key Terms:

• Law of Conservation of Mass: States that mass is conserved in a chemical reaction.

• Dalton's Atomic Theory: Early theory about the nature of atoms.

• Law of Multiple Proportions: Relates to ratios of elements in compounds.

• Law of Definite Proportions: States that a chemical compound always contains the same elements in the same proportion by mass.

Step-by-Step Guidance

1. Read the statement carefully and identify what it is describing about matter during a chemical reaction.

2. Recall which law specifically addresses the conservation of mass in reactions.

3. Compare the statement to the definitions of the laws listed in the answer choices.

Try solving on your own before revealing the answer!

Final Answer: A) the Law of Conservation of Mass

This law states that mass is neither created nor destroyed in a chemical reaction, matching the statement given.

Q2. Which description identifies a solid?

Background

Topic: States of Matter

This question tests your understanding of the physical properties of solids, liquids, and gases.

Key Terms:

• Solid: Definite shape and definite volume.

• Liquid: Definite volume, no definite shape.

• Gas: No definite shape or volume.

Step-by-Step Guidance

1. Review the properties of solids, liquids, and gases.

2. Identify which option matches the definition of a solid.

3. Eliminate choices that do not have both definite shape and definite volume.

Try solving on your own before revealing the answer!

Final Answer: A) definite volume and definite shape

Solids have both a definite shape and a definite volume.

Q3. Determine the density of an object with a mass of 149.8 g and a volume of 12.1 mL.

Background

Topic: Density Calculations

This question tests your ability to calculate density using mass and volume.

Key formula:

$\text{Density} = \frac{\text{Mass}}{\text{Volume}}$

Where:

• Mass = 149.8 g

• Volume = 12.1 mL

Step-by-Step Guidance

1. Write down the formula for density: $\text{Density} = \frac{\text{Mass}}{\text{Volume}}$

2. Plug in the given values: $\text{Density} = \frac{149.8\ \text{g}}{12.1\ \text{mL}}$

3. Set up the division, but do not calculate the final value yet.

4. Consider significant figures: Both mass and volume have 3 significant figures, so your answer should as well.

Try solving on your own before revealing the answer!

Final Answer: A) 12.4 g/mL

Dividing 149.8 g by 12.1 mL gives 12.4 g/mL, rounded to three significant figures.

Q4. What answer should be reported, with the correct number of significant figures, for (965.43 × 3.911) + 9413.4136?

Background

Topic: Significant Figures in Calculations

This question tests your ability to apply rules for significant figures in multiplication and addition.

Key Terms and Rules:

• Multiplication: The result should have the same number of significant figures as the factor with the fewest.

• Addition: The result should be rounded to the least precise decimal place.

Step-by-Step Guidance

1. Multiply 965.43 by 3.911. Both numbers have 5 significant figures, so the product should have 5 significant figures.

2. Add the product to 9413.4136. The sum should be rounded to the decimal place of the least precise number.

3. Check the answer choices for proper significant figure reporting.

Try solving on your own before revealing the answer!

Final Answer: B) 13189.2

The answer is rounded to the correct number of significant figures based on the rules for multiplication and addition.

Q5. Convert 65°C to °F.

Background

Topic: Temperature Conversion

This question tests your ability to convert between Celsius and Fahrenheit.

Key formula:

$\text{°F} = \left(\frac{9}{5} \times \text{°C}\right) + 32$

Step-by-Step Guidance

1. Write the conversion formula: $\text{°F} = \left(\frac{9}{5} \times \text{°C}\right) + 32$

2. Plug in 65 for °C: $\text{°F} = \left(\frac{9}{5} \times 65\right) + 32$

3. Calculate $\frac{9}{5} \times 65$ first, then add 32.

Try solving on your own before revealing the answer!

Final Answer: A) 149°F

Using the formula, 65°C converts to 149°F.

Q6. What element does "X" represent in the given symbol?

Background

Topic: Element Symbols

This question tests your knowledge of chemical element symbols.

Key Terms:

• Element symbols: Each element has a unique one- or two-letter symbol.

Step-by-Step Guidance

1. Recall which element has the symbol "X" (if any).

2. Compare the answer choices to the periodic table and their symbols.

3. Eliminate options that do not match the symbol "X".

Try solving on your own before revealing the answer!

Final Answer: None of the listed elements have the symbol "X".

"X" is not a standard element symbol. Check the periodic table for confirmation.

Q7. Calculate the atomic mass of silver given two isotopes: Ag-107 (106.90509 amu, 51.84%) and Ag-109 (108.90476 amu, 48.46%).

Background

Topic: Isotopic Abundance and Atomic Mass

This question tests your ability to calculate the weighted average atomic mass using isotopic masses and abundances.

Key formula:

$\text{Atomic mass} = (\text{mass}_1 \times \text{fraction}_1) + (\text{mass}_2 \times \text{fraction}_2)$

Where:

• mass1 = 106.90509 amu

• fraction1 = 0.5184

• mass2 = 108.90476 amu

• fraction2 = 0.4846

Step-by-Step Guidance

1. Convert the percent abundances to decimal fractions: 51.84% = 0.5184, 48.46% = 0.4846.

2. Multiply each isotope's mass by its fractional abundance.

3. Add the two products to get the weighted average atomic mass.

Try solving on your own before revealing the answer!

Final Answer: C) 107.90 amu

The weighted average gives the atomic mass of silver.

Q8. What mass (in mg) does 2.63 moles of nickel have?

Background

Topic: Moles and Mass Conversion

This question tests your ability to convert moles to mass using molar mass and unit conversions.

Key formula:

$\text{Mass (g)} = \text{moles} \times \text{molar mass (g/mol)}$

$\text{Mass (mg)} = \text{Mass (g)} \times 1000$

Where:

• Moles = 2.63

• Molar mass of Ni = 58.69 g/mol

Step-by-Step Guidance

1. Multiply the number of moles by the molar mass to get mass in grams: $2.63 \times 58.69$

2. Convert the mass in grams to milligrams by multiplying by 1000.

3. Set up the calculation, but do not compute the final value yet.

Try solving on your own before revealing the answer!

Final Answer: D) 1.54 × 105 mg

Multiplying moles by molar mass and converting to mg gives the correct mass.

Q9. What is the name for H2CO3?

Background

Topic: Naming Acids

This question tests your knowledge of acid nomenclature, specifically for oxoacids.

Key Terms:

• Oxoacid: An acid containing hydrogen, oxygen, and another element.

• "-ic" ending: Used for acids with the "-ate" polyatomic ion.

Step-by-Step Guidance

1. Identify the polyatomic ion in H2CO3 (CO32- is carbonate).

2. Apply the naming rule: If the ion ends in "-ate", the acid name ends in "-ic".

3. Combine the root name with "acid" to form the correct name.

Try solving on your own before revealing the answer!

Final Answer: C) carbonic acid

H2CO3 is named carbonic acid because it contains the carbonate ion.

Q10. Write the formula for the compound formed between aluminum and sulfur.

Background

Topic: Ionic Compound Formulas

This question tests your ability to write formulas for ionic compounds based on the charges of the ions.

Key Terms:

• Aluminum ion: Al3+

• Sulfide ion: S2−

Step-by-Step Guidance

1. Write the charges for aluminum (Al3+) and sulfur (S2−).

2. Balance the charges to get a neutral compound. Find the lowest common multiple of the charges.

3. Write the formula using subscripts to indicate the number of each ion needed for neutrality.

Try solving on your own before revealing the answer!

Final Answer: A) Al2S3

Two aluminum ions and three sulfide ions combine to form a neutral compound.