Intro to Chemistry Exam 1 Review – Step-by-Step Study Guidance

Q1. What is a scientific hypothesis?

Background

Topic: Scientific Method

This question tests your understanding of the definition and characteristics of a scientific hypothesis in the context of scientific inquiry.

Key Terms:

• Hypothesis: A proposed explanation for an observation, which can be tested through experimentation.

• Scientific Method: The process used to investigate observations, solve problems, and test hypotheses.

Step-by-Step Guidance

1. Recall that a hypothesis is an initial explanation that can be tested by experiments or observations.

2. Consider whether a hypothesis is considered absolute, complex, simple, or tentative. Think about whether it is meant to be a final answer or a starting point for investigation.

3. Review the definitions of each answer choice and eliminate those that do not fit the scientific method's approach to hypotheses.

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Q2. Which of the following is NOT true for a scientific law?

Background

Topic: Scientific Laws vs. Theories

This question asks you to distinguish between what a scientific law is and what it is not, especially compared to theories and hypotheses.

Key Terms:

• Scientific Law: A statement that summarizes a pattern found in nature, often expressed mathematically.

• Scientific Theory: An explanation of why phenomena occur, based on evidence.

Step-by-Step Guidance

1. Review what a scientific law does: does it summarize data, explain data, or both?

2. Consider which answer choice describes something that is not a function of a scientific law.

3. Recall that laws are often mathematical and universal, but do not provide explanations for why phenomena occur.

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Q4. On Mars, gravity is one-third that on Earth. What would be the weight on Mars of a person who has a weight of 150 pounds on Earth?

Background

Topic: Weight and Gravity

This question tests your understanding of how weight depends on gravitational force and how to calculate weight on different planets.

Key Terms and Formula:

• Weight: The force exerted on an object due to gravity, calculated as mass times gravitational acceleration.

• Formula: $\text{Weight on Mars} = \text{Weight on Earth} \times \left( \frac{g_{\text{Mars}}}{g_{\text{Earth}}} \right)$

Step-by-Step Guidance

1. Identify the weight on Earth: 150 lb.

2. Recognize that gravity on Mars is one-third that of Earth, so $g_{\text{Mars}} / g_{\text{Earth}} = 1/3$.

3. Set up the calculation: multiply the Earth weight by 1/3 to find the Mars weight.

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Q12. How many meters are in 10.0 cm?

Background

Topic: Metric Conversions

This question tests your ability to convert between centimeters and meters using metric prefixes.

Key Terms and Formula:

• centi- (c): Prefix meaning 1/100 or $10^{-2}$.

• Conversion: $1 \text{ cm} = 0.01 \text{ m}$

Step-by-Step Guidance

1. Write the given value: 10.0 cm.

2. Set up the conversion factor: $1 \text{ cm} = 0.01 \text{ m}$.

3. Multiply the number of centimeters by the conversion factor to get meters.

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Q15. The density of a certain type of steel is 8.1 g/cm3. What is the mass of a 100.0 cm3 chunk of this steel?

Background

Topic: Density Calculations

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

Key Formula:

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

• Rearranged: $\text{Mass} = \text{Density} \times \text{Volume}$

Step-by-Step Guidance

1. Identify the given values: density = 8.1 g/cm3, volume = 100.0 cm3.

2. Write the formula for mass: $\text{Mass} = \text{Density} \times \text{Volume}$.

3. Plug in the values to set up the calculation.

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Q23. Calculate how many moles are in 17.0 grams of H2O2

Background

Topic: Moles and Molar Mass

This question tests your ability to convert grams to moles using the molar mass of a compound.

Key Terms and Formula:

• Mole: The amount of substance containing Avogadro's number of particles (6.022 × 1023).

• Molar Mass: The mass of one mole of a substance, in grams per mole.

• Formula: $\text{Moles} = \frac{\text{Mass (g)}}{\text{Molar Mass (g/mol)}}$

Step-by-Step Guidance

1. Write the given mass: 17.0 g of H2O2.

2. Calculate the molar mass of H2O2: add the atomic masses of all atoms in the formula.

3. Set up the calculation using the formula above.

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Q25. Calculate the grams present in 0.200 moles of H2

Background

Topic: Moles to Mass Conversion

This question tests your ability to convert from moles to grams using the molar mass of hydrogen gas.

Key Terms and Formula:

• Mole: A counting unit for atoms/molecules.

• Molar Mass of H2: The mass of one mole of H2 molecules.

• Formula: $\text{Mass (g)} = \text{Moles} \times \text{Molar Mass (g/mol)}$

Step-by-Step Guidance

1. Write the given amount: 0.200 moles of H2.

2. Calculate the molar mass of H2 (remember, H = 1.01 g/mol).

3. Set up the calculation using the formula above.

Try solving on your own before revealing the answer!