Q: Convert 0.250 kilometers to inches. (Use the conversion factors: 1 km = 1000 m, 1 m = 39.37 in.)

$$0.250 \times 1000 \times 39.37 = 9842.5$$ inches

Q: A 100.0 g sample of water is heated from 25.0°C to 75.0°C. How much energy (in joules) is absorbed? (Specific heat of water = 4.184 J/g°C)

$$q = 100.0 \times 4.184 \times (75.0 - 25.0) = 20,920 J$$

Q: A sample contains 80.0% $$^{63}Cu ($$atomic mass = 62.93 u) and 20.0% $$^{65}Cu ($$atomic mass = 64.93 u). What is the average atomic mass of copper?

$$0.800 \times 62.93 + 0.200 \times 64.93 = 63.33 u$$

Q: A 250.0 g sample of aluminum (specific heat = 0.903 J/g°C) cools from 100.0°C to 25.0°C. How much heat is released?

$$q = 250.0 \times 0.903 \times (25.0 - 100.0) = -16,943 J$$

Q: A student converts 0.00560 kg to milligrams. What is the correct answer?

$$0.00560 \times 10^6$ = 5600 mg$$

Question 1

A student measures the mass of a metal sample as 15.0 g and its volume as 2.00 cm$$^3. $$Based on the densities in Table 2.4, which metal is the sample most likely to be?

Accepted Answer

Lead

Question 2

Which of the following best describes the difference between accuracy and precision in scientific measurements?

Accepted Answer

Accuracy refers to how close measurements are to the true value, while precision refers to how close measurements are to each other.

Question 3

Convert 0.250 kilometers to inches. (Use the conversion factors: 1 km = 1000 m, 1 m = 39.37 in.)

Accepted Answer

$$0.250 	imes 1000 	imes 39.37 = 9842.5$$ inches

Question 4

A sample of ethanol (density = 0.789 g/cm$$^3) $$has a mass of 50.0 g. What is its volume in mL?

Accepted Answer

$$\frac{50.0}{0.789} = 63.4 mL$$

Question 5

Which of the following is a heterogeneous mixture?

Accepted Answer

Sand and iron filings

Question 6

Which of the following changes is a chemical change?

Accepted Answer

Burning wood

Question 7

A 100.0 g sample of water is heated from 25.0°C to 75.0°C. How much energy (in joules) is absorbed? (Specific heat of water = 4.184 J/g°C)

Accepted Answer

$$q = 100.0 	imes 4.184 	imes (75.0 - 25.0) = 20,920 J$$

Question 8

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes of an element have the same number of protons but different numbers of neutrons.

Question 9

Which of the following elements is a noble gas?

Accepted Answer

Neon

Question 10

A sample contains 80.0% $$^{63}Cu ($$atomic mass = 62.93 u) and 20.0% $$^{65}Cu ($$atomic mass = 64.93 u). What is the average atomic mass of copper?

Accepted Answer

$$0.800 	imes 62.93 + 0.200 	imes 64.93 = 63.33 u$$

Question 11

Which of the following is the correct SI unit for measuring temperature?

Accepted Answer

Kelvin

Question 12

A 250.0 g sample of aluminum (specific heat = 0.903 J/g°C) cools from 100.0°C to 25.0°C. How much heat is released?

Accepted Answer

$$q = 250.0 	imes 0.903 	imes (25.0 - 100.0) = -16,943 J$$

Question 13

Which of the following is a physical property?

Accepted Answer

Density

Question 14

Which of the following best describes an exothermic reaction?

Accepted Answer

A reaction that releases heat to the surroundings

Question 15

Convert 2.50 quarts to liters. (Use the conversion factor: 1 L = 1.057 quarts)

Accepted Answer

$$2.50 \div 1.057 = 2.37 L$$

Question 16

Which of the following is a derived unit in the SI system?

Accepted Answer

Joule

Question 17

A student converts 0.00560 kg to milligrams. What is the correct answer?

Accepted Answer

$$0.00560 	imes 10^6$ = 5600 mg$$

Question 18

Which of the following best describes a cation?

Accepted Answer

An atom that has lost electrons

Question 19

Which of the following is a correct application of the law of conservation of mass?

Accepted Answer

The total mass of reactants equals the total mass of products in a chemical reaction.

Question 20

A sample of gas is at 25°C. What is its temperature in Kelvin?

Accepted Answer

$$25 + 273.15 = 298.15 K$$

Introductory Chemistry: Measurement, Matter, and Atomic Structure Study Guide

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