Q1. A student is 175 cm tall. This corresponds to 1.75 m.

Background

Topic: Unit Conversion (Metric System)

This question tests your understanding of converting between centimeters and meters, a fundamental skill in chemistry for working with SI units.

Key Terms:

• Centimeter (cm): 1/100 of a meter

• Meter (m): Base unit of length in the metric system

Key formula:

Step-by-Step Guidance

1. Identify the given value: 175 cm.

2. Recall the conversion factor between centimeters and meters.

3. Set up the conversion:

4. Plug in the value for centimeters and simplify, but do not calculate the final answer yet.

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Q2. (8.50 × 103) – (7.61 × 102) = 7.739 × 103 to the correct number of significant figures.

Background

Topic: Significant Figures in Calculations

This question tests your ability to apply rules for significant figures when performing subtraction with numbers in scientific notation.

Key Terms:

• Significant Figures: Digits that carry meaning contributing to a measurement's precision.

• Scientific Notation: A way to express very large or small numbers.

Key formula:

When subtracting, the answer should have the same decimal place as the least precise measurement.

Step-by-Step Guidance

1. Write both numbers with the same exponent for easier subtraction: and .

2. Subtract the numbers: .

3. Determine the correct number of significant figures based on the original values.

4. Express the result in scientific notation, rounding to the correct number of significant figures.

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Q3. One kg is equal to 2.205 pounds. I wish to convert a patient’s weight from pounds to kg. I would use the conversion factor .

Background

Topic: Unit Conversion (Mass)

This question tests your understanding of how to use conversion factors to convert between pounds and kilograms.

Key Terms:

• Kilogram (kg): SI unit of mass

• Pound (lb): Common unit of mass in the US

• Conversion Factor: Ratio used to convert from one unit to another

Key formula:

Step-by-Step Guidance

1. Identify the direction of conversion: pounds to kilograms.

2. Recall the conversion factor: .

3. Set up the conversion so that pounds cancel and kilograms remain.

4. Check if the given conversion factor is set up correctly for this direction.

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Q4. The element carbon is in Period 2, group IVA (14).

Background

Topic: Periodic Table Organization

This question tests your ability to locate elements on the periodic table and understand their period and group assignments.

Key Terms:

• Period: Horizontal row in the periodic table

• Group: Vertical column in the periodic table

Step-by-Step Guidance

1. Locate carbon (C) on the periodic table.

2. Identify the period number (row) for carbon.

3. Identify the group number (column) for carbon.

4. Check if carbon is in Period 2 and Group 14 (IVA).

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Q5. The atomic number for an atom is different from that of its ion. For example, sodium has 11 protons while the sodium ion has only 10 protons.

Background

Topic: Atomic Number and Ions

This question tests your understanding of atomic number and the difference between atoms and ions.

Key Terms:

• Atomic Number: Number of protons in the nucleus

• Ion: Atom that has gained or lost electrons

Step-by-Step Guidance

1. Recall that atomic number is defined by the number of protons.

2. Consider what happens when an atom becomes an ion (gains or loses electrons).

3. Check if the number of protons changes when forming an ion.

4. Compare the atomic number of sodium atom and sodium ion.

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Q6. Based on their position in the periodic table we would predict that atomic radius increases from P to S to Cl.

Background

Topic: Periodic Trends (Atomic Radius)

This question tests your understanding of how atomic radius changes across a period in the periodic table.

Key Terms:

• Atomic Radius: Distance from nucleus to outermost electron

• Periodic Trend: Predictable change in properties across the table

Step-by-Step Guidance

1. Recall the trend for atomic radius across a period: it generally decreases from left to right.

2. Locate P, S, and Cl in the same period (Period 3).

3. Compare their positions and predict the trend in atomic radius.

4. Determine if the statement matches the expected trend.

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Q7. Nonmetals tend to gain electrons to become anions.

Background

Topic: Chemical Properties of Nonmetals

This question tests your understanding of how nonmetals form ions.

Key Terms:

• Anion: Negatively charged ion

• Nonmetal: Element that tends to gain electrons

Step-by-Step Guidance

1. Recall the general behavior of nonmetals in chemical reactions.

2. Consider how nonmetals achieve a stable electron configuration.

3. Determine if gaining electrons to form anions is typical for nonmetals.

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Q8. The polyatomic ion chlorite has the formula ClO2−. Based on rules for naming polyatomic ions, chlorate would have the formula ClO3−.

Background

Topic: Polyatomic Ion Naming

This question tests your understanding of the naming conventions for polyatomic ions containing oxygen.

Key Terms:

• Chlorite: ClO2−

• Chlorate: ClO3−

• Polyatomic Ion: Ion composed of more than one atom

Step-by-Step Guidance

1. Recall the naming pattern for oxyanions: "-ite" has fewer oxygens than "-ate".

2. Compare the formulas for chlorite and chlorate.

3. Determine if the formula for chlorate is correct based on the rules.

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Q9. An acceptable Lewis structure for the polyatomic ion carbonate is shown to the right.

Background

Topic: Lewis Structures for Polyatomic Ions

This question tests your ability to recognize correct Lewis structures for polyatomic ions.

Key Terms:

• Lewis Structure: Diagram showing bonding and lone pairs

• Polyatomic Ion: Ion with multiple atoms

• Carbonate: CO32−

Step-by-Step Guidance

1. Recall the correct Lewis structure for carbonate ion.

2. Check for correct number of bonds and lone pairs.

3. Verify the charge and arrangement of atoms.

4. Compare the given structure to the accepted structure.

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Q10. Electronegativity tends to decrease as you go down a group.

Background

Topic: Periodic Trends (Electronegativity)

This question tests your understanding of how electronegativity changes within a group in the periodic table.

Key Terms:

• Electronegativity: Ability of an atom to attract electrons

• Group: Vertical column in the periodic table

Step-by-Step Guidance

1. Recall the trend for electronegativity down a group.

2. Consider why electronegativity changes as atomic size increases.

3. Determine if the statement matches the expected trend.

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