Chemistry A Semester Exam Practice Quiz

Which of the following best describes why elements in the same group on the periodic table have similar properties?

• They have the same number of protons

• They have the same number of valence electrons

• They have the same atomic radius

• They are in the same period

Answer explanation

Elements in the same group have similar properties because they have the same number of valence electrons. This similarity in valence electrons leads to comparable chemical behavior and reactivity.

Tags

NGSS.HS-PS1-1

NGSS.HS-PS1-2

Table salt (NaCl) can be classified as which of the following?

1. Element

2. Compound

3. Pure substance

4. Mixture

• Compound and pure substance

• Element and compound

• Element and pure substance

• Compound and mixture

Answer explanation

Table salt (NaCl) is a compound because it consists of two elements, sodium and chlorine, chemically combined. It is also a pure substance as it has a uniform composition throughout, distinguishing it from mixtures.

Tags

NGSS.MS-PS1-1

Which piece of laboratory equipment is best suited for measuring 25 mL of a liquid accurately?

• Beaker

• Graduated Cylinder

• Erlenmeyer Flask

• Test Tube

Answer explanation

A graduated cylinder is designed for precise volume measurements, making it the best choice for accurately measuring 25 mL of liquid. Beakers and flasks are less accurate, while test tubes are not suitable for this volume.

Which of the following statements correctly explains the difference between mass and weight?

• Mass is the force of gravity on an object, while weight is the amount of matter in an object

• Mass depends on an object's location, while weight is constant everywhere

• Mass is the amount of matter in an object, while weight is the force of gravity acting on that mass

• Mass and weight are the same and can be used interchangeably

Answer explanation

The correct choice states that mass is the amount of matter in an object, while weight is the force of gravity acting on that mass. This distinction is crucial, as mass remains constant, whereas weight varies with gravity.

Tags

NGSS.MS-PS2-4

How many significant figures does the number 0.004520 have?

• 3

• 4

• 5

• 6

Answer explanation

The number 0.004520 has four significant figures. The leading zeros (0.00) are not counted, but the digits 4, 5, and 2, along with the trailing zero (0) after 2, are significant.

How many significant figures does the result of the following calculation have?

45.62 m − 3.1 m

• 1

• 2

• 3

• 4

Answer explanation

In the calculation 45.62 m − 3.1 m, the number of significant figures is determined by the least precise measurement. 3.1 m has 2 significant figures, so the result should also have 2 significant figures.

If 1,000 milliliters (mL) is equal to 1 liter (L), then how many liters are in 253 mL? Report your answer to three significant figures.

• 0.25 L

• 0.253 L

• 0.2530 L

• 0.3 L

Answer explanation

To convert 253 mL to liters, divide by 1000 (since 1000 mL = 1 L). Thus, 253 mL = 0.253 L. The answer is reported to three significant figures, making 0.253 L the correct choice.

What is dimensional analysis used for?

• To convert between different units of measurement

• To analyze chemical reactions and predict products

• To balance chemical equations

• To calculate the density of a substance

Answer explanation

Dimensional analysis is a method used to convert between different units of measurement by analyzing the dimensions of the quantities involved. This makes it the correct choice, as the other options pertain to different concepts.

What atomic model did Rutherford propose?

• The planetary model

• The electron cloud model

• The nuclear model

• The quantum mechanical mode

Answer explanation

Rutherford proposed the nuclear model of the atom, which describes a dense nucleus surrounded by orbiting electrons, contrasting with earlier models like the planetary model.

The natural abundances and atomic masses are used to calculate average atomic mass. What is the average atomic mass of chlorine? Report your answer in four significant figures.

• 35.45 amu

• 36.13 amu

• 34.85 amu

• 37.02 amu

Answer explanation

The average atomic mass of chlorine is calculated using its isotopes' natural abundances and atomic masses. The most common value, 35.45 amu, reflects the weighted average of its isotopes, making it the correct choice.