$$1.51 \times 10$$^{23}$$ atoms

Question 1

Which of the following statements best describes a chemical property of matter?

Accepted Answer

It is the ability of a substance to undergo a change in composition under stated conditions.

Question 2

A sample of ice melts into water. Which type of change has occurred, and why?

Accepted Answer

A physical change, because the composition of H$$_2O $$remains the same.

Question 3

Which of the following is a heterogeneous mixture?

Accepted Answer

Sand and iron filings

Question 4

Which separation technique would be most appropriate to separate a mixture of sand and water?

Accepted Answer

Filtration

Question 5

Which of the following statements about the states of matter is correct?

Accepted Answer

In a gas, particles are far apart and move freely to fill the container.

Question 6

Which SI base unit is used to measure the amount of substance?

Accepted Answer

Mole ($$mol)$$

Question 7

A student measures the mass of a cube as 15.0 g and its volume as 5.0 cm$$^3. $$What is the density of the cube?

Accepted Answer

$$3.0\ g/cm^3$

Question 8

A seawater sample contains 3.5% NaCl by mass. How many grams of NaCl are present in 200 g of seawater?

Accepted Answer

$$7.0\ g$$

Question 9

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

Accepted Answer

Accuracy refers to how close a measurement is to the true value, while precision refers to the reproducibility of measurements.

Question 10

How many significant figures are in the measurement 0.004004500?

Accepted Answer

7

Question 11

Which law states that the total mass of substances present after a chemical reaction is the same as the total mass before the reaction?

Accepted Answer

Law of Conservation of Mass

Question 12

A compound is found to contain 11.19% hydrogen and 88.81% oxygen by mass. Which law does this observation support?

Accepted Answer

Law of Constant Composition

Question 13

Which experiment led to the discovery of the electron’s charge?

Accepted Answer

Millikan’s oil-drop experiment

Question 14

Which atomic model describes electrons embedded in a diffuse cloud of positive charge?

Accepted Answer

Thomson’s plum-pudding model

Question 15

Which of the following statements about isotopes is correct?

Accepted Answer

Isotopes have the same atomic number but different mass numbers.

Question 16

A neutral atom of $$^{16}O $$has how many protons, neutrons, and electrons?

Accepted Answer

8 protons, 8 neutrons, 8 electrons

Question 17

Which of the following is the correct value for Avogadro’s number?

Accepted Answer

$$6.022 	imes 10$$^{23}$$

Question 18

How many atoms are present in 0.250 mol of sulfur ($$S$$)?

Accepted Answer

$$1.51 	imes 10$$^{23}$$ atoms

Question 19

A student rounds the number 7.5647 to three significant figures. What is the correct result?

Accepted Answer

7.56

Question 20

Which of the following best explains why density is considered an intensive property?

Accepted Answer

Density does not depend on the amount of substance present.

Matter and Its Properties: Foundations of General Chemistry

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