Exam #1 Practice Questions – Step-by-Step Study Guidance for GOB Chemistry

Q1. Round off 00707508 to four significant figures.

Background

Topic: Significant Figures

This question tests your understanding of how to round numbers to a specified number of significant digits, which is essential for reporting scientific measurements accurately.

Key Terms:

• Significant Figures: The digits in a number that carry meaning contributing to its precision.

• Rounding: Adjusting a number to reduce the number of digits while keeping its value close to the original.

Step-by-Step Guidance

1. Identify the first four nonzero digits in the number 00707508. Ignore leading zeros as they are not significant.

2. Count out the first four significant digits from left to right.

3. Look at the digit immediately after the fourth significant figure to determine if you need to round up or keep the digit the same.

Try solving on your own before revealing the answer!

Q2. Osmium has a density of 22.6 g/cm3. What volume (in cm3) would be occupied by a 21.8 g sample of osmium?

Background

Topic: Density Calculations

This question tests your ability to use the density formula to solve for volume when given mass and density.

Key Formula:

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

To solve for volume:

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

• Mass (g)

• Density (g/cm3)

• Volume (cm3)

Step-by-Step Guidance

1. Write down the given values: mass = 21.8 g, density = 22.6 g/cm3.

2. Set up the formula to solve for volume: $\text{Volume} = \frac{\text{Mass}}{\text{Density}}$

3. Plug the given values into the formula, making sure units are consistent.

Try solving on your own before revealing the answer!

Q3. The mass number for an isotope containing 29 protons, 29 electrons, and 34 neutrons is

Background

Topic: Atomic Structure – Isotopes

This question tests your understanding of how to determine the mass number of an isotope based on its subatomic particles.

Key Terms and Formula:

• Mass Number (A): The sum of protons and neutrons in the nucleus.

• Protons: Positively charged particles in the nucleus.

• Neutrons: Neutral particles in the nucleus.

$\text{Mass Number} = \text{Number of Protons} + \text{Number of Neutrons}$

Step-by-Step Guidance

1. Identify the number of protons (given: 29).

2. Identify the number of neutrons (given: 34).

3. Add the number of protons and neutrons to find the mass number.

Try solving on your own before revealing the answer!

Q4. Elements in the Periodic Table are arranged according to

Background

Topic: Periodic Table Organization

This question tests your knowledge of how elements are ordered in the periodic table.

Key Terms:

• Atomic Number: The number of protons in the nucleus of an atom.

• Periodic Table: A chart of elements arranged by increasing atomic number.

Step-by-Step Guidance

1. Recall what property increases sequentially as you move from left to right and top to bottom in the periodic table.

2. Consider whether elements are arranged by atomic mass, atomic number, or another property.

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Q5. If 1.4% of the mass of a human body is calcium, how many kilograms of calcium are there in a 185-pound man?

Background

Topic: Percent Composition and Unit Conversion

This question tests your ability to use percentages and convert between units (pounds to kilograms).

Key Terms and Formulas:

• Percent Composition: The percentage by mass of a component in a mixture or compound.

• Unit Conversion: 1 kg = 2.20 lb

Step-by-Step Guidance

1. Convert the body mass from pounds to kilograms using the conversion factor.

2. Calculate the mass of calcium by multiplying the total body mass (in kg) by the percentage (as a decimal).

Try solving on your own before revealing the answer!

Q6. Where is most of the mass of an atom concentrated?

Background

Topic: Atomic Structure

This question tests your understanding of the distribution of mass within an atom.

Key Terms:

• Nucleus: The dense center of an atom containing protons and neutrons.

• Electron Cloud: The region around the nucleus where electrons are found.

Step-by-Step Guidance

1. Recall which subatomic particles contribute most to the mass of an atom.

2. Determine where these particles are located within the atom.

Try solving on your own before revealing the answer!