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 figures, which is important for reporting measurements in chemistry.

Key Terms:

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

• Rounding: Adjusting a number to a specified degree of accuracy.

Step-by-Step Guidance

1. Identify the first four nonzero digits in the number 00707508. Leading zeros 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: $\text{Volume} = \frac{\text{Mass}}{\text{Density}}$

Step-by-Step Guidance

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

2. Rearrange the density formula to solve for volume.

3. Substitute the given values into the rearranged formula.

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:

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

• Protons: Positively charged particles in the nucleus.

• Neutrons: Neutral particles in the nucleus.

Step-by-Step Guidance

1. Recall the formula: $\text{Mass Number} = \text{Number of Protons} + \text{Number of Neutrons}$

2. Identify the number of protons and neutrons from the question.

3. Add the two values together 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 organized in the periodic table, which is fundamental to understanding chemical properties and trends.

Key Terms:

• Atomic Number: The number of protons in the nucleus of an atom, unique to each element.

• Periodic Table: A tabular arrangement of elements based on increasing atomic number.

Step-by-Step Guidance

1. Recall what property is used to order elements in the periodic table.

2. Consider how this property affects the arrangement and periodic trends.

Try solving on your own before revealing the answer!

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) to find the mass of a component in a sample.

Key Formulas and Conversions:

• Percent by mass: $\text{Mass of component} = \text{Total mass} \times \frac{\text{Percent}}{100}$

• Unit conversion: $1 \text{ kg} = 2.20 \text{ lb}$

Step-by-Step Guidance

1. Convert the body mass from pounds to kilograms using the given 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 structure of the atom and where its mass is primarily located.

Key Terms:

• Nucleus: The dense central core of an atom, containing protons and neutrons.

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

Step-by-Step Guidance

1. Recall the relative masses of protons, neutrons, and electrons.

2. Consider where protons and neutrons are located within the atom.

3. Determine which part of the atom contains nearly all the mass.

Try solving on your own before revealing the answer!