Q: If a sample contains 3.25 mol of iron, how many iron atoms are present?

$$1.96 \times 10$$^{24}$$ atoms

Q: How many lead atoms are in 0.224 g of lead? (Molar mass of Pb = 207.2 g/mol)

$$6.51 \times 10$$^{20}$$ atoms

Question 1

Which law states that in a chemical reaction, the total mass of the substances involved does not change?

Accepted Answer

Law of Conservation of Mass

Question 2

A sample of sodium oxide from three sources shows a sodium-to-oxygen mass ratio of 2.87:1 in each sample. Which law does this observation support?

Accepted Answer

Law of Definite Proportions

Question 3

Copper and chlorine form two compounds: one with a mass ratio of 0.558 g Cl to 1 g Cu, and another with 1.116 g Cl to 1 g Cu. What is the ratio of chlorine masses, and which law does this illustrate?

Accepted Answer

Ratio is $$\frac{1.116}{0.558} = 2$$; Law of Multiple Proportions

Question 4

Which postulate of Dalton’s atomic theory is inconsistent with the existence of isotopes?

Accepted Answer

Each atom of a given element has the same characteristic mass and other properties.

Question 5

What is the most important number for identifying an atom as a particular element?

Accepted Answer

Number of protons

Question 6

Which of the following is the correct nuclide symbol for an isotope with 10 protons and 12 neutrons?

Accepted Answer

$$\frac{22}{10}	ext{Ne}$$

Question 7

A neutral atom of lithium has 3 protons and 3 electrons. What is the charge of the ion formed when it loses one electron?

Accepted Answer

$$+1$$

Question 8

Which group in the periodic table tends to form ions with a $$+2$$ charge?

Accepted Answer

Group 2A (alkaline earth metals)

Question 9

What is the charge of the ion formed by a main-group element in group 7A?

Accepted Answer

$$-1$$

Question 10

Which property is characteristic of metals in the periodic table?

Accepted Answer

Can be drawn into wires (ductility)

Question 11

Calculate the average atomic mass of neon given the following isotopic abundances: Ne-20 (90.48%, 20 amu), Ne-21 (0.27%, 21 amu), Ne-22 (9.25%, 22 amu).

Accepted Answer

$$20.18$$ amu

Question 12

Which device is used to measure the masses of atoms and molecules by separating ions based on their mass-to-charge ratio?

Accepted Answer

Mass spectrometer

Question 13

If a sample contains 3.25 mol of iron, how many iron atoms are present?

Accepted Answer

$$1.96 	imes 10$$^{24}$$ atoms

Question 14

How many moles of silver atoms are in 7.811 g of silver? (Molar mass of Ag = 107.87 g/mol)

Accepted Answer

$$7.24 	imes 10$$^{-2}$$ mol

Question 15

Which element has the smallest molar mass among aluminum, carbon, and helium?

Accepted Answer

Helium

Question 16

A compound is analyzed and found to contain 4.45 g fluorine and 1.25 g sulfur. Another compound contains 4.43 g fluorine and 1.87 g sulfur. What law do these data illustrate?

Accepted Answer

Law of Multiple Proportions

Question 17

Which statement best describes the behavior of isotopes of the same element?

Accepted Answer

They generally exhibit the same chemical behavior.

Question 18

What is the molar mass of an element whose atomic mass is 26.98 amu?

Accepted Answer

$$26.98 g/$$mol

Question 19

How many lead atoms are in 0.224 g of lead? (Molar mass of Pb = 207.2 g/mol)

Accepted Answer

$$6.51 	imes 10$$^{20}$$ atoms

Question 20

Which of the following is NOT a property of nonmetals?

Accepted Answer

Can be drawn into wires (ductility)

Atoms and Elements: Foundations of Modern Chemistry

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