Q: A sample contains $0.50$ mol of $\mathrm{CO}_2$. How many molecules are present in the sample? (Use Avogadro’s number: $6.022 \times 10^{23}$ mol$^{-1}$)

$3.01 \times 10^{23}$ molecules

Question 1

Which of the following best describes the difference between qualitative and quantitative measurements in the scientific method?

Accepted Answer

Qualitative measurements involve descriptions, while quantitative measurements involve numbers.

Question 2

Convert $4.56 	imes 10^3$ to standard decimal notation.

Accepted Answer

$4560$

Question 3

Which of the following is the correct number of significant figures in the measurement $0.00450$?

Accepted Answer

3

Question 4

A student measures the mass of a sample as $12.34$ g and the volume as $4.0$ mL. What is the density of the sample, and how many significant figures should the answer have?

Accepted Answer

$3.1$ g/mL, 2 significant figures

Question 5

Which of the following statements about Dalton’s atomic theory is NOT correct based on modern understanding?

Accepted Answer

Atoms of a given element are identical in mass and properties.

Question 6

Which scientist is credited with discovering the electron using cathode ray experiments?

Accepted Answer

Thomson

Question 7

How many protons, neutrons, and electrons are in a neutral atom of $^{23}_{11}\mathrm{Na}$?

Accepted Answer

11 protons, 12 neutrons, 11 electrons

Question 8

Which of the following is a chemical property?

Accepted Answer

Reactivity with oxygen

Question 9

Which of the following elements is an alkaline earth metal?

Accepted Answer

Magnesium ($\mathrm{Mg}$)

Question 10

A sample contains $0.50$ mol of $\mathrm{CO}_2$. How many molecules are present in the sample? (Use Avogadro’s number: $6.022 	imes 10^{23}$ mol$^{-1}$)

Accepted Answer

$3.01 	imes 10^{23}$ molecules

Question 11

Which of the following compounds is an ionic compound?

Accepted Answer

$\mathrm{NaCl}$

Question 12

What is the correct name for $\mathrm{Fe}_2\mathrm{O}_3$?

Accepted Answer

Iron(III) oxide

Question 13

Which of the following best describes a covalent bond?

Accepted Answer

A bond formed by the sharing of electrons between two nonmetals

Question 14

How many electrons are in the $\mathrm{Cl}^-$ ion?

Accepted Answer

18

Question 15

Which of the following is a mixture?

Accepted Answer

Air

Question 16

Convert $25.0$ grams of $\mathrm{H}_2\mathrm{O}$ to moles. (Molar mass of $\mathrm{H}_2\mathrm{O}$ is $18.0$ g/mol)

Accepted Answer

$1.39$ mol

Question 17

Which of the following is the correct electron configuration for a neutral atom of sodium ($\mathrm{Na}$, atomic number 11)?

Accepted Answer

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

Question 18

Which of the following statements about isotopes is correct?

Accepted Answer

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

Question 19

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

Accepted Answer

$\mathrm{MgCl}_2$

Question 20

A compound contains $40.0\%$ carbon, $6.7\%$ hydrogen, and $53.3\%$ oxygen by mass. What is the empirical formula of the compound?

Accepted Answer

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

Exam 1 Study Guide: Chemical Tools, Atoms, Molecules & Ions

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