Question 1

Which experiment provided evidence that atoms are mostly empty space with a small, dense, positively charged nucleus?

Accepted Answer

Rutherford's gold foil experiment

Question 2

Which of the following statements is NOT part of Dalton's Atomic Theory?

Accepted Answer

Atoms are made of protons, neutrons, and electrons.

Question 3

A sample of magnesium contains three isotopes: $^{24}\mathrm{Mg}$ (78.99%, 23.985 amu), $^{25}\mathrm{Mg}$ (10.00%, 24.986 amu), and $^{26}\mathrm{Mg}$ (11.01%, 25.983 amu). What is the weighted average atomic mass of magnesium? (Round to two decimal places.)

Accepted Answer

$24.31\ \mathrm{amu}$

Question 4

Which of the following ions is correctly matched with its group and predicted charge?

Accepted Answer

Chloride ion, Group 7A, $-1$

Question 5

Which of the following best describes a polyatomic ion?

Accepted Answer

A charged species composed of two or more atoms covalently bonded

Question 6

What is the empirical formula of a compound that is 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass?

Accepted Answer

$\mathrm{CH}_2\mathrm{O}$

Question 7

Which of the following is the correct name for the compound $\mathrm{FeCl}_3$?

Accepted Answer

Iron(III) chloride

Question 8

How many molecules are present in $0.50$ moles of $\mathrm{CO}_2$?

Accepted Answer

$3.01 	imes 10^{23}$

Question 9

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

Accepted Answer

They have a full valence shell of electrons.

Question 10

A compound has an empirical formula of $\mathrm{CH}_2\mathrm{O}$ and a molar mass of $180\ \mathrm{g/mol}$. What is its molecular formula?

Accepted Answer

$\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6$

Question 11

Which of the following is a correct statement of the Law of Constant Composition?

Accepted Answer

A given compound always contains the same proportion of elements by mass.

Question 12

What is the mass percent of oxygen in water ($\mathrm{H}_2\mathrm{O}$)? (Atomic masses: H = 1.01, O = 16.00)

Accepted Answer

$88.8\%$

Question 13

Which of the following best describes a transition element?

Accepted Answer

An element in Groups 1B–8B with variable charges

Question 14

Which of the following is the correct formula for calcium sulfate, given that the sulfate ion is $\mathrm{SO}_4^{2-}$?

Accepted Answer

$\mathrm{CaSO}_4$

Question 15

If you have $18.0\ \mathrm{g}$ of glucose ($\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6$), how many moles do you have? (Molar mass = $180\ \mathrm{g/mol}$)

Accepted Answer

$0.10$ moles

Question 16

Which of the following is the correct name for $\mathrm{HCl}$ (aq)?

Accepted Answer

Hydrochloric acid

Question 17

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

Accepted Answer

The empirical formula shows the simplest whole-number ratio of atoms, while the molecular formula shows the actual number of atoms in a molecule.

Question 18

Which of the following is a correct formula for an ionic compound formed between magnesium and nitrogen?

Accepted Answer

$\mathrm{Mg}_3\mathrm{N}_2$

Question 19

Which of the following statements about subatomic particles is correct?

Accepted Answer

The mass of a proton is approximately equal to the mass of a neutron.

Question 20

A sample contains $1.204 	imes 10^{24}$ molecules of $\mathrm{H}_2\mathrm{O}$. How many moles of water does this represent?

Accepted Answer

$2.00$ moles

Atoms, Elements, Compounds, and the Mole: Foundational Concepts in Chemistry

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