Q: A sample of magnesium contains three naturally occurring isotopes: $$^{24}Mg (78.99$$%), $$^{25}Mg (10.00$$%), and $$^{26}Mg (11.01$$%). Which of the following best describes the calculation for the average atomic mass of magnesium?

$$(24 \times 0.7899) + (25 \times 0.1000) + (26 \times 0.1101)$$

Question 1

Which of the following statements best describes Dalton's Law of Constant Composition?

Accepted Answer

A given compound always contains the same relative number and kind of atoms.

Question 2

A neutral atom of phosphorus has an atomic number of 15 and a mass number of 31. How many neutrons does it have?

Accepted Answer

$$31 - 15 = 16$$ neutrons

Question 3

Which of the following is the correct empirical formula for glucose, whose molecular formula is $$C_6H_{12}O_6$?

Accepted Answer

$$CH_2O$$

Question 4

Which of the following elements is a halogen?

Accepted Answer

Chlorine

Question 5

What is the correct name for the compound $$FeCl_3$$?

Accepted Answer

Iron(III) chloride

Question 6

Which of the following ions is isoelectronic with neon ($$Ne$$)?

Accepted Answer

$$F^-$$

Question 7

A sample of magnesium contains three naturally occurring isotopes: $$^{24}Mg (78.99$$%), $$^{25}Mg (10.00$$%), and $$^{26}Mg (11.01$$%). Which of the following best describes the calculation for the average atomic mass of magnesium?

Accepted Answer

$$(24 	imes 0.7899) + (25 	imes 0.1000) + (26 	imes 0.1101)$$

Question 8

Which of the following is the correct formula for ammonium sulfate?

Accepted Answer

$$(NH_4$)_2SO_4$$

Question 9

Which of the following best describes the difference between a molecular formula and an empirical formula?

Accepted Answer

A molecular formula shows the actual number of atoms in a molecule, while an empirical formula shows the lowest whole-number ratio of atoms.

Question 10

Which of the following compounds is named correctly?

Accepted Answer

$$N_2O_4 = $$dinitrogen tetroxide

Question 11

Which of the following is the correct name for $$H_2SO_4$$?

Accepted Answer

Sulfuric acid

Question 12

A certain ion has 17 protons, 18 neutrons, and 18 electrons. What is its symbol?

Accepted Answer

$$^{35}Cl^-$$

Question 13

Which of the following best explains why elements in the same group of the periodic table have similar chemical properties?

Accepted Answer

They have the same number of valence electrons.

Question 14

Which of the following is the correct formula for magnesium nitride?

Accepted Answer

$$Mg_3N_2$$

Question 15

Which of the following is a correct statement about isotopes?

Accepted Answer

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

Question 16

Which of the following is the correct name for $$Na_2CO_3$$?

Accepted Answer

Sodium carbonate

Question 17

A compound is found to contain 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. What is its empirical formula?

Accepted Answer

$$CH_2O$$

Question 18

Which of the following is the correct formula for calcium phosphate?

Accepted Answer

$$Ca_3$$($$PO_4)_2$

Question 19

Which of the following best describes a cation?

Accepted Answer

An atom or molecule that has lost one or more electrons

Question 20

Which of the following is the correct name for $$KNO_3$$?

Accepted Answer

Potassium nitrate

Atoms, Molecules, and Ions: Foundations of Chemical Structure and Nomenclature

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