Q: A 2.00 L sample of a gas at STP contains how many molecules? (STP: 1 mol gas = 22.4 L)

$5.38 \times 10^{22}$ molecules

Question 1

A sample of an unknown metal has a mass of 45.0 g and a volume of 16.0 mL. What is the density of the metal?

Accepted Answer

$2.81 \, \mathrm{g/mL}$

Question 2

Which of the following best describes a heterogeneous mixture?

Accepted Answer

A mixture in which the composition is not uniform throughout

Question 3

A student measures the mass of a sample three times and gets values of 2.01 g, 2.03 g, and 2.02 g. The true mass is 2.50 g. Which statement best describes the accuracy and precision of the measurements?

Accepted Answer

The measurements are precise but not accurate

Question 4

Which of the following is an example of a physical change?

Accepted Answer

Melting of ice

Question 5

A naturally occurring element has two isotopes: $X$-10 (mass = 10.01 amu, abundance = 19.91%) and $X$-11 (mass = 11.01 amu, abundance = 80.09%). What is the atomic mass of element $X$?

Accepted Answer

$10.81 \, \mathrm{amu}$

Question 6

How many atoms are present in 0.250 moles of copper ($\mathrm{Cu}$)? (Avogadro's number $= 6.022 	imes 10^{23}$ atoms/mol)

Accepted Answer

$1.51 	imes 10^{24}$ atoms

Question 7

Which of the following elements is a metalloid?

Accepted Answer

Silicon

Question 8

A sample contains $3.00 	imes 10^{22}$ molecules of water. How many moles of water are present?

Accepted Answer

$0.050 \, \mathrm{mol}$

Question 9

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

Accepted Answer

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

Question 10

Which of the following is a chemical property?

Accepted Answer

Reactivity with acid

Question 11

A 5.00 g sample of magnesium reacts with oxygen to form magnesium oxide. If the final mass of magnesium oxide is 8.30 g, what mass of oxygen reacted?

Accepted Answer

$3.30 \, \mathrm{g}$

Question 12

Which of the following statements about isotopes is TRUE?

Accepted Answer

Isotopes of the same element have the same number of protons

Question 13

Which of the following is the correct name for $\mathrm{N}_2\mathrm{O}_5$?

Accepted Answer

Dinitrogen pentoxide

Question 14

A compound contains 27.3% carbon and 72.7% oxygen by mass. What is the empirical formula?

Accepted Answer

$\mathrm{CO}_2$

Question 15

Which of the following is a molecular compound?

Accepted Answer

$\mathrm{CO}_2$

Question 16

A 2.00 L sample of a gas at STP contains how many molecules? (STP: 1 mol gas = 22.4 L)

Accepted Answer

$5.38 	imes 10^{22}$ molecules

Question 17

Which of the following is the correct name for $\mathrm{Fe}_2\mathrm{O}_3$?

Accepted Answer

Iron(III) oxide

Question 18

Which of the following is NOT a physical property?

Accepted Answer

Flammability

Question 19

A sample of sodium chloride ($\mathrm{NaCl}$) contains $3.01 	imes 10^{23}$ formula units. What is the mass of the sample? ($M_{\mathrm{NaCl}} = 58.44 \, \mathrm{g/mol}$)

Accepted Answer

$29.2 \, \mathrm{g}$

Question 20

Which of the following elements is a halogen?

Accepted Answer

Chlorine

General Chemistry: Foundations, Atoms, Elements, Molecules, and Compounds – Study Guide

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