$$0.0500 \times 58.44 = 2.92 g$$

$$(0.5184 \times 106.90509) + (0.4816 \times 108.90476) = 107.87$$ amu

$$6 \times 6.022 \times 10$$^{23}$$

Question 1

Which of the following statements best explains why noble gases are generally unreactive?

Accepted Answer

They have a full valence shell, satisfying the octet rule.

Question 2

A sample contains 0.0500 mol of sodium chloride (NaCl). What is the mass of this sample? (Molar mass of NaCl = 58.44 g/mol)

Accepted Answer

$$0.0500 	imes 58.44 = 2.92 g$$

Question 3

Which of the following pairs are isotopes of the same element?

Accepted Answer

An atom with 7 protons and 8 neutrons, and an atom with 7 protons and 7 neutrons

Question 4

How many valence electrons does a chlorine atom have?

Accepted Answer

7

Question 5

Which of the following best describes the difference between atomic mass and mass number?

Accepted Answer

Atomic mass is the weighted average of all isotopes, while mass number is the sum of protons and neutrons in a specific atom.

Question 6

A neutral atom of magnesium has an atomic number of 12. What is its electron configuration?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$

Question 7

Which of the following elements is a metalloid?

Accepted Answer

Silicon (Si)

Question 8

How many molecules are present in 18.02 g of water ($$H_2O$$)? (Molar mass of $$H_2O = 18.02 g/$$mol)

Accepted Answer

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

Question 9

Which of the following statements about electron shells is correct?

Accepted Answer

The maximum number of electrons in the second shell is 8.

Question 10

A sample of silver contains 51.84% $$^{107}Ag (106.90509 $$amu) and 48.16% $$^{109}Ag (108.90476 $$amu). What is the average atomic mass of silver?

Accepted Answer

$$(0.5184 	imes 106.90509) + (0.4816 	imes 108.90476) = 107.87$$ amu

Question 11

Which of the following best describes a compound?

Accepted Answer

A substance composed of two or more elements chemically combined in a fixed ratio.

Question 12

How many atoms of oxygen are in 1 mole of glucose ($$C_6H_{12}O_6$)?

Accepted Answer

$$6 	imes 6.022 	imes 10$$^{23}$$

Question 13

Which of the following is the correct Lewis dot structure for nitrogen (N)?

Accepted Answer

N with 5 dots around it

Question 14

Which of the following statements about the periodic table is true?

Accepted Answer

Elements in the same group have the same number of valence electrons.

Question 15

A neutral atom has 15 protons, 16 neutrons, and 15 electrons. What is its atomic number and mass number?

Accepted Answer

Atomic number = 15, Mass number = 31

Question 16

Which of the following is a property of metalloids?

Accepted Answer

They conduct electricity poorly.

Question 17

How many moles are in 25.0 g of $$CO_2$$? (Molar mass of $$CO_2 = 44.01$ g/mol)

Accepted Answer

$$\frac{25.0}{44.01} = 0.568$$ mol

Question 18

Which of the following best describes the relationship between the number of protons and the identity of an element?

Accepted Answer

The number of protons determines the element's identity.

Question 19

Which of the following is the correct formula for calculating the number of entities in a given number of moles?

Accepted Answer

$$	ext{Number of entities} = n 	imes 6.022 	imes 10$$^{23}$$

Atoms, Elements, and Compounds: Foundations of Modern Chemistry

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