Question 1

A laboratory technician measures the mass of a sample four times and records the following values: 2.51 g, 2.49 g, 2.50 g, and 2.52 g. The true mass is 2.80 g. Which statement best describes the technician's measurements?

Accepted Answer

The measurements are precise but not accurate.

Question 2

Which of the following numbers has the correct number of significant figures after rounding 0.0045678 to three significant figures?

Accepted Answer

0.00456

Question 3

Express 5,430,000 in scientific notation with three significant figures.

Accepted Answer

$$5.43 	imes 10^6$

Question 4

A student adds 12.345 g and 1.2 g. According to the rules for significant figures in addition, what is the correct sum?

Accepted Answer

13.5 g

Question 5

Convert 250 milliliters (mL) to liters (L).

Accepted Answer

$$0.25\ 	ext{L}$$

Question 6

Which of the following is a chemical change?

Accepted Answer

Burning wood

Question 7

Which of the following best describes air?

Accepted Answer

A homogeneous mixture

Question 8

Which statement correctly describes the properties of solids compared to gases?

Accepted Answer

Solids have definite shape and volume, while gases have neither.

Question 9

Which intermolecular force is primarily responsible for water's high boiling point?

Accepted Answer

Hydrogen bonding

Question 10

Convert 37°C to Kelvin.

Accepted Answer

$$310\ 	ext{K}$$

Question 11

Which of the following is an example of an exothermic process?

Accepted Answer

Combustion of gasoline

Question 12

A block has a mass of 150 g and a volume of 50 cm³. What is its density?

Accepted Answer

$$3.0\ 	ext{g/cm}^3$$

Question 13

A sample of gas occupies 2.0 L at 1.0 atm. If the pressure increases to 4.0 atm and the temperature remains constant, what will the new volume be? (Use Boyle's Law: $$P_1V_1 = P_2V_2)$$

Accepted Answer

$$0.5\ 	ext{L}$$

Question 14

Which of the following best describes a heterogeneous mixture?

Accepted Answer

Sand in water

Question 15

A student multiplies 2.50 (3 sig figs) by 0.040 (2 sig figs). According to the rules for significant figures in multiplication, how many significant figures should the answer have?

Accepted Answer

2

Question 16

Which of the following statements about gases is correct?

Accepted Answer

Gases are compressible and expand to fill their container.

Question 17

Which metric unit would be most appropriate for measuring the mass of a small insect?

Accepted Answer

Milligram (mg)

Question 18

A metal sample is heated and its temperature rises from 25°C to 75°C. What is the change in temperature in Kelvin?

Accepted Answer

$$50\ 	ext{K}$$

Question 19

Which of the following is a pure substance?

Accepted Answer

Distilled water

Question 20

A balloon contains 3.0 L of gas at 300 K. If the temperature increases to 600 K and the pressure remains constant, what will the new volume be? (Use Charles's Law: $$\frac{V_1$}{T_1$} = \frac{V_2$}{T_2$})$$

Accepted Answer

$$6.0\ 	ext{L}$$

CHEM 100 Exam I: Essential Concepts and Calculations

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