$5.0 \times \frac{1 \text{ mol}}{4.003 \text{ g}} \times \frac{6.022 \times 10^{23} \text{ atoms}}{1 \text{ mol}}$

$1.67 \times 10^{21}$ molecules

$\text{mass (g)} \xrightarrow{\div \text{molar mass}} \text{moles} \xrightarrow{\times N_A} \text{particles}$

$6.022 \times 10^{23}$ formula units

Question 1

Which of the following best describes Avogadro's number?

Accepted Answer

The number of atoms in 12 grams of carbon-12.

Question 2

A sample contains $3.01 	imes 10^{23}$ molecules of CO$_2$. How many moles of CO$_2$ are present?

Accepted Answer

$0.25$ mol

Question 3

What is the mass in grams of $2.5$ moles of sodium chloride (NaCl)? (Na: $22.99$ g/mol, Cl: $35.45$ g/mol)

Accepted Answer

$146.1$ g

Question 4

Which of the following statements about the mole is correct?

Accepted Answer

A mole is always 6.022 x $10^{23}$ particles, regardless of the substance.

Question 5

How many atoms are present in $10.0$ grams of aluminum (Al)? (Al: $26.98$ g/mol)

Accepted Answer

$2.23 	imes 10^{23}$ atoms

Question 6

Which calculation correctly converts $5.0$ grams of helium (He) to the number of atoms? (He: $4.003$ g/mol)

Accepted Answer

$5.0 	imes \frac{1 	ext{ mol}}{4.003 	ext{ g}} 	imes \frac{6.022 	imes 10^{23} 	ext{ atoms}}{1 	ext{ mol}}$

Question 7

What is the molecular mass of glucose, C$_6$H$_{12}$O$_6$? (C: $12.01$ amu, H: $1.01$ amu, O: $16.00$ amu)

Accepted Answer

$180.16$ amu

Question 8

A can of soda contains $16.2$ grams of aluminum (Al). How many atoms of aluminum are in the can? (Al: $26.98$ g/mol)

Accepted Answer

$3.62 	imes 10^{23}$ atoms

Question 9

Which of the following best explains why the mole is a useful unit in chemistry?

Accepted Answer

It allows chemists to count atoms and molecules by weighing them.

Question 10

What is the formula mass of Fe$_2$O$_3$? (Fe: $55.85$ amu, O: $16.00$ amu)

Accepted Answer

$159.70$ amu

Question 11

A drop of water contains $2.77 	imes 10^{-3}$ moles of H$_2$O. How many molecules of H$_2$O are in the drop?

Accepted Answer

$1.67 	imes 10^{21}$ molecules

Question 12

Which of the following is the correct relationship between mass, moles, and number of particles?

Accepted Answer

$	ext{mass (g)} \xrightarrow{\div 	ext{molar mass}} 	ext{moles} \xrightarrow{	imes N_A} 	ext{particles}$

Question 13

If you have $1.00$ mole of NaCl, how many formula units of NaCl do you have?

Accepted Answer

$6.022 	imes 10^{23}$ formula units

Question 14

A chemist needs $0.500$ moles of Fe$_2$O$_3$ for a reaction. What mass of Fe$_2$O$_3$ should be weighed out? (Fe$_2$O$_3$ molar mass: $159.70$ g/mol)

Accepted Answer

$79.85$ g

Question 15

Which of the following is the correct molar mass for potassium fluoride (KF)? (K: $39.10$ g/mol, F: $19.00$ g/mol)

Accepted Answer

$58.10$ g/mol

Question 16

A patient receives an intravenous solution containing $0.90$ grams of NaCl. How many moles of NaCl does this represent? (NaCl: $58.44$ g/mol)

Accepted Answer

$0.015$ mol

Question 17

Which of the following best describes the difference between molecular mass and formula mass?

Accepted Answer

Molecular mass is for covalent compounds, formula mass is for ionic compounds.

Question 18

How many oxygen atoms are in $0.250$ moles of glucose (C$_6$H$_{12}$O$_6$)?

Accepted Answer

$1.51 	imes 10^{24}$ atoms

The Mole Concept, Molar Mass, and Molecular/Formula Mass in General Chemistry

Study Guide - Practice Questions